Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2206 insertions, 0 deletions

diff --git a/drivers/hwtracing/intel_th/msu.c b/drivers/hwtracing/intel_th/msu.c
new file mode 100644
index 000000000..6c8215a47
--- /dev/null
+++ b/drivers/hwtracing/intel_th/msu.c
@@ -0,0 +1,2206 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Intel(R) Trace Hub Memory Storage Unit
+ *
+ * Copyright (C) 2014-2015 Intel Corporation.
+ */
+
+#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
+
+#include <linux/types.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/uaccess.h>
+#include <linux/sizes.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/mm.h>
+#include <linux/fs.h>
+#include <linux/io.h>
+#include <linux/workqueue.h>
+#include <linux/dma-mapping.h>
+
+#ifdef CONFIG_X86
+#include <asm/set_memory.h>
+#endif
+
+#include <linux/intel_th.h>
+#include "intel_th.h"
+#include "msu.h"
+
+#define msc_dev(x) (&(x)->thdev->dev)
+
+/*
+ * Lockout state transitions:
+ *   READY -> INUSE -+-> LOCKED -+-> READY -> etc.
+ *                   \-----------/
+ * WIN_READY:	window can be used by HW
+ * WIN_INUSE:	window is in use
+ * WIN_LOCKED:	window is filled up and is being processed by the buffer
+ * handling code
+ *
+ * All state transitions happen automatically, except for the LOCKED->READY,
+ * which needs to be signalled by the buffer code by calling
+ * intel_th_msc_window_unlock().
+ *
+ * When the interrupt handler has to switch to the next window, it checks
+ * whether it's READY, and if it is, it performs the switch and tracing
+ * continues. If it's LOCKED, it stops the trace.
+ */
+enum lockout_state {
+	WIN_READY = 0,
+	WIN_INUSE,
+	WIN_LOCKED
+};
+
+/**
+ * struct msc_window - multiblock mode window descriptor
+ * @entry:	window list linkage (msc::win_list)
+ * @pgoff:	page offset into the buffer that this window starts at
+ * @lockout:	lockout state, see comment below
+ * @lo_lock:	lockout state serialization
+ * @nr_blocks:	number of blocks (pages) in this window
+ * @nr_segs:	number of segments in this window (<= @nr_blocks)
+ * @_sgt:	array of block descriptors
+ * @sgt:	array of block descriptors
+ */
+struct msc_window {
+	struct list_head	entry;
+	unsigned long		pgoff;
+	enum lockout_state	lockout;
+	spinlock_t		lo_lock;
+	unsigned int		nr_blocks;
+	unsigned int		nr_segs;
+	struct msc		*msc;
+	struct sg_table		_sgt;
+	struct sg_table		*sgt;
+};
+
+/**
+ * struct msc_iter - iterator for msc buffer
+ * @entry:		msc::iter_list linkage
+ * @msc:		pointer to the MSC device
+ * @start_win:		oldest window
+ * @win:		current window
+ * @offset:		current logical offset into the buffer
+ * @start_block:	oldest block in the window
+ * @block:		block number in the window
+ * @block_off:		offset into current block
+ * @wrap_count:		block wrapping handling
+ * @eof:		end of buffer reached
+ */
+struct msc_iter {
+	struct list_head	entry;
+	struct msc		*msc;
+	struct msc_window	*start_win;
+	struct msc_window	*win;
+	unsigned long		offset;
+	struct scatterlist	*start_block;
+	struct scatterlist	*block;
+	unsigned int		block_off;
+	unsigned int		wrap_count;
+	unsigned int		eof;
+};
+
+/**
+ * struct msc - MSC device representation
+ * @reg_base:		register window base address
+ * @thdev:		intel_th_device pointer
+ * @mbuf:		MSU buffer, if assigned
+ * @mbuf_priv		MSU buffer's private data, if @mbuf
+ * @win_list:		list of windows in multiblock mode
+ * @single_sgt:		single mode buffer
+ * @cur_win:		current window
+ * @nr_pages:		total number of pages allocated for this buffer
+ * @single_sz:		amount of data in single mode
+ * @single_wrap:	single mode wrap occurred
+ * @base:		buffer's base pointer
+ * @base_addr:		buffer's base address
+ * @user_count:		number of users of the buffer
+ * @mmap_count:		number of mappings
+ * @buf_mutex:		mutex to serialize access to buffer-related bits
+
+ * @enabled:		MSC is enabled
+ * @wrap:		wrapping is enabled
+ * @mode:		MSC operating mode
+ * @burst_len:		write burst length
+ * @index:		number of this MSC in the MSU
+ */
+struct msc {
+	void __iomem		*reg_base;
+	void __iomem		*msu_base;
+	struct intel_th_device	*thdev;
+
+	const struct msu_buffer	*mbuf;
+	void			*mbuf_priv;
+
+	struct work_struct	work;
+	struct list_head	win_list;
+	struct sg_table		single_sgt;
+	struct msc_window	*cur_win;
+	struct msc_window	*switch_on_unlock;
+	unsigned long		nr_pages;
+	unsigned long		single_sz;
+	unsigned int		single_wrap : 1;
+	void			*base;
+	dma_addr_t		base_addr;
+	u32			orig_addr;
+	u32			orig_sz;
+
+	/* <0: no buffer, 0: no users, >0: active users */
+	atomic_t		user_count;
+
+	atomic_t		mmap_count;
+	struct mutex		buf_mutex;
+
+	struct list_head	iter_list;
+
+	bool			stop_on_full;
+
+	/* config */
+	unsigned int		enabled : 1,
+				wrap	: 1,
+				do_irq	: 1,
+				multi_is_broken : 1;
+	unsigned int		mode;
+	unsigned int		burst_len;
+	unsigned int		index;
+};
+
+static LIST_HEAD(msu_buffer_list);
+static DEFINE_MUTEX(msu_buffer_mutex);
+
+/**
+ * struct msu_buffer_entry - internal MSU buffer bookkeeping
+ * @entry:	link to msu_buffer_list
+ * @mbuf:	MSU buffer object
+ * @owner:	module that provides this MSU buffer
+ */
+struct msu_buffer_entry {
+	struct list_head	entry;
+	const struct msu_buffer	*mbuf;
+	struct module		*owner;
+};
+
+static struct msu_buffer_entry *__msu_buffer_entry_find(const char *name)
+{
+	struct msu_buffer_entry *mbe;
+
+	lockdep_assert_held(&msu_buffer_mutex);
+
+	list_for_each_entry(mbe, &msu_buffer_list, entry) {
+		if (!strcmp(mbe->mbuf->name, name))
+			return mbe;
+	}
+
+	return NULL;
+}
+
+static const struct msu_buffer *
+msu_buffer_get(const char *name)
+{
+	struct msu_buffer_entry *mbe;
+
+	mutex_lock(&msu_buffer_mutex);
+	mbe = __msu_buffer_entry_find(name);
+	if (mbe && !try_module_get(mbe->owner))
+		mbe = NULL;
+	mutex_unlock(&msu_buffer_mutex);
+
+	return mbe ? mbe->mbuf : NULL;
+}
+
+static void msu_buffer_put(const struct msu_buffer *mbuf)
+{
+	struct msu_buffer_entry *mbe;
+
+	mutex_lock(&msu_buffer_mutex);
+	mbe = __msu_buffer_entry_find(mbuf->name);
+	if (mbe)
+		module_put(mbe->owner);
+	mutex_unlock(&msu_buffer_mutex);
+}
+
+int intel_th_msu_buffer_register(const struct msu_buffer *mbuf,
+				 struct module *owner)
+{
+	struct msu_buffer_entry *mbe;
+	int ret = 0;
+
+	mbe = kzalloc(sizeof(*mbe), GFP_KERNEL);
+	if (!mbe)
+		return -ENOMEM;
+
+	mutex_lock(&msu_buffer_mutex);
+	if (__msu_buffer_entry_find(mbuf->name)) {
+		ret = -EEXIST;
+		kfree(mbe);
+		goto unlock;
+	}
+
+	mbe->mbuf = mbuf;
+	mbe->owner = owner;
+	list_add_tail(&mbe->entry, &msu_buffer_list);
+unlock:
+	mutex_unlock(&msu_buffer_mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(intel_th_msu_buffer_register);
+
+void intel_th_msu_buffer_unregister(const struct msu_buffer *mbuf)
+{
+	struct msu_buffer_entry *mbe;
+
+	mutex_lock(&msu_buffer_mutex);
+	mbe = __msu_buffer_entry_find(mbuf->name);
+	if (mbe) {
+		list_del(&mbe->entry);
+		kfree(mbe);
+	}
+	mutex_unlock(&msu_buffer_mutex);
+}
+EXPORT_SYMBOL_GPL(intel_th_msu_buffer_unregister);
+
+static inline bool msc_block_is_empty(struct msc_block_desc *bdesc)
+{
+	/* header hasn't been written */
+	if (!bdesc->valid_dw)
+		return true;
+
+	/* valid_dw includes the header */
+	if (!msc_data_sz(bdesc))
+		return true;
+
+	return false;
+}
+
+static inline struct scatterlist *msc_win_base_sg(struct msc_window *win)
+{
+	return win->sgt->sgl;
+}
+
+static inline struct msc_block_desc *msc_win_base(struct msc_window *win)
+{
+	return sg_virt(msc_win_base_sg(win));
+}
+
+static inline dma_addr_t msc_win_base_dma(struct msc_window *win)
+{
+	return sg_dma_address(msc_win_base_sg(win));
+}
+
+static inline unsigned long
+msc_win_base_pfn(struct msc_window *win)
+{
+	return PFN_DOWN(msc_win_base_dma(win));
+}
+
+/**
+ * msc_is_last_win() - check if a window is the last one for a given MSC
+ * @win:	window
+ * Return:	true if @win is the last window in MSC's multiblock buffer
+ */
+static inline bool msc_is_last_win(struct msc_window *win)
+{
+	return win->entry.next == &win->msc->win_list;
+}
+
+/**
+ * msc_next_window() - return next window in the multiblock buffer
+ * @win:	current window
+ *
+ * Return:	window following the current one
+ */
+static struct msc_window *msc_next_window(struct msc_window *win)
+{
+	if (msc_is_last_win(win))
+		return list_first_entry(&win->msc->win_list, struct msc_window,
+					entry);
+
+	return list_next_entry(win, entry);
+}
+
+static size_t msc_win_total_sz(struct msc_window *win)
+{
+	struct scatterlist *sg;
+	unsigned int blk;
+	size_t size = 0;
+
+	for_each_sg(win->sgt->sgl, sg, win->nr_segs, blk) {
+		struct msc_block_desc *bdesc = sg_virt(sg);
+
+		if (msc_block_wrapped(bdesc))
+			return (size_t)win->nr_blocks << PAGE_SHIFT;
+
+		size += msc_total_sz(bdesc);
+		if (msc_block_last_written(bdesc))
+			break;
+	}
+
+	return size;
+}
+
+/**
+ * msc_find_window() - find a window matching a given sg_table
+ * @msc:	MSC device
+ * @sgt:	SG table of the window
+ * @nonempty:	skip over empty windows
+ *
+ * Return:	MSC window structure pointer or NULL if the window
+ *		could not be found.
+ */
+static struct msc_window *
+msc_find_window(struct msc *msc, struct sg_table *sgt, bool nonempty)
+{
+	struct msc_window *win;
+	unsigned int found = 0;
+
+	if (list_empty(&msc->win_list))
+		return NULL;
+
+	/*
+	 * we might need a radix tree for this, depending on how
+	 * many windows a typical user would allocate; ideally it's
+	 * something like 2, in which case we're good
+	 */
+	list_for_each_entry(win, &msc->win_list, entry) {
+		if (win->sgt == sgt)
+			found++;
+
+		/* skip the empty ones */
+		if (nonempty && msc_block_is_empty(msc_win_base(win)))
+			continue;
+
+		if (found)
+			return win;
+	}
+
+	return NULL;
+}
+
+/**
+ * msc_oldest_window() - locate the window with oldest data
+ * @msc:	MSC device
+ *
+ * This should only be used in multiblock mode. Caller should hold the
+ * msc::user_count reference.
+ *
+ * Return:	the oldest window with valid data
+ */
+static struct msc_window *msc_oldest_window(struct msc *msc)
+{
+	struct msc_window *win;
+
+	if (list_empty(&msc->win_list))
+		return NULL;
+
+	win = msc_find_window(msc, msc_next_window(msc->cur_win)->sgt, true);
+	if (win)
+		return win;
+
+	return list_first_entry(&msc->win_list, struct msc_window, entry);
+}
+
+/**
+ * msc_win_oldest_sg() - locate the oldest block in a given window
+ * @win:	window to look at
+ *
+ * Return:	index of the block with the oldest data
+ */
+static struct scatterlist *msc_win_oldest_sg(struct msc_window *win)
+{
+	unsigned int blk;
+	struct scatterlist *sg;
+	struct msc_block_desc *bdesc = msc_win_base(win);
+
+	/* without wrapping, first block is the oldest */
+	if (!msc_block_wrapped(bdesc))
+		return msc_win_base_sg(win);
+
+	/*
+	 * with wrapping, last written block contains both the newest and the
+	 * oldest data for this window.
+	 */
+	for_each_sg(win->sgt->sgl, sg, win->nr_segs, blk) {
+		struct msc_block_desc *bdesc = sg_virt(sg);
+
+		if (msc_block_last_written(bdesc))
+			return sg;
+	}
+
+	return msc_win_base_sg(win);
+}
+
+static struct msc_block_desc *msc_iter_bdesc(struct msc_iter *iter)
+{
+	return sg_virt(iter->block);
+}
+
+static struct msc_iter *msc_iter_install(struct msc *msc)
+{
+	struct msc_iter *iter;
+
+	iter = kzalloc(sizeof(*iter), GFP_KERNEL);
+	if (!iter)
+		return ERR_PTR(-ENOMEM);
+
+	mutex_lock(&msc->buf_mutex);
+
+	/*
+	 * Reading and tracing are mutually exclusive; if msc is
+	 * enabled, open() will fail; otherwise existing readers
+	 * will prevent enabling the msc and the rest of fops don't
+	 * need to worry about it.
+	 */
+	if (msc->enabled) {
+		kfree(iter);
+		iter = ERR_PTR(-EBUSY);
+		goto unlock;
+	}
+
+	iter->msc = msc;
+
+	list_add_tail(&iter->entry, &msc->iter_list);
+unlock:
+	mutex_unlock(&msc->buf_mutex);
+
+	return iter;
+}
+
+static void msc_iter_remove(struct msc_iter *iter, struct msc *msc)
+{
+	mutex_lock(&msc->buf_mutex);
+	list_del(&iter->entry);
+	mutex_unlock(&msc->buf_mutex);
+
+	kfree(iter);
+}
+
+static void msc_iter_block_start(struct msc_iter *iter)
+{
+	if (iter->start_block)
+		return;
+
+	iter->start_block = msc_win_oldest_sg(iter->win);
+	iter->block = iter->start_block;
+	iter->wrap_count = 0;
+
+	/*
+	 * start with the block with oldest data; if data has wrapped
+	 * in this window, it should be in this block
+	 */
+	if (msc_block_wrapped(msc_iter_bdesc(iter)))
+		iter->wrap_count = 2;
+
+}
+
+static int msc_iter_win_start(struct msc_iter *iter, struct msc *msc)
+{
+	/* already started, nothing to do */
+	if (iter->start_win)
+		return 0;
+
+	iter->start_win = msc_oldest_window(msc);
+	if (!iter->start_win)
+		return -EINVAL;
+
+	iter->win = iter->start_win;
+	iter->start_block = NULL;
+
+	msc_iter_block_start(iter);
+
+	return 0;
+}
+
+static int msc_iter_win_advance(struct msc_iter *iter)
+{
+	iter->win = msc_next_window(iter->win);
+	iter->start_block = NULL;
+
+	if (iter->win == iter->start_win) {
+		iter->eof++;
+		return 1;
+	}
+
+	msc_iter_block_start(iter);
+
+	return 0;
+}
+
+static int msc_iter_block_advance(struct msc_iter *iter)
+{
+	iter->block_off = 0;
+
+	/* wrapping */
+	if (iter->wrap_count && iter->block == iter->start_block) {
+		iter->wrap_count--;
+		if (!iter->wrap_count)
+			/* copied newest data from the wrapped block */
+			return msc_iter_win_advance(iter);
+	}
+
+	/* no wrapping, check for last written block */
+	if (!iter->wrap_count && msc_block_last_written(msc_iter_bdesc(iter)))
+		/* copied newest data for the window */
+		return msc_iter_win_advance(iter);
+
+	/* block advance */
+	if (sg_is_last(iter->block))
+		iter->block = msc_win_base_sg(iter->win);
+	else
+		iter->block = sg_next(iter->block);
+
+	/* no wrapping, sanity check in case there is no last written block */
+	if (!iter->wrap_count && iter->block == iter->start_block)
+		return msc_iter_win_advance(iter);
+
+	return 0;
+}
+
+/**
+ * msc_buffer_iterate() - go through multiblock buffer's data
+ * @iter:	iterator structure
+ * @size:	amount of data to scan
+ * @data:	callback's private data
+ * @fn:		iterator callback
+ *
+ * This will start at the window which will be written to next (containing
+ * the oldest data) and work its way to the current window, calling @fn
+ * for each chunk of data as it goes.
+ *
+ * Caller should have msc::user_count reference to make sure the buffer
+ * doesn't disappear from under us.
+ *
+ * Return:	amount of data actually scanned.
+ */
+static ssize_t
+msc_buffer_iterate(struct msc_iter *iter, size_t size, void *data,
+		   unsigned long (*fn)(void *, void *, size_t))
+{
+	struct msc *msc = iter->msc;
+	size_t len = size;
+	unsigned int advance;
+
+	if (iter->eof)
+		return 0;
+
+	/* start with the oldest window */
+	if (msc_iter_win_start(iter, msc))
+		return 0;
+
+	do {
+		unsigned long data_bytes = msc_data_sz(msc_iter_bdesc(iter));
+		void *src = (void *)msc_iter_bdesc(iter) + MSC_BDESC;
+		size_t tocopy = data_bytes, copied = 0;
+		size_t remaining = 0;
+
+		advance = 1;
+
+		/*
+		 * If block wrapping happened, we need to visit the last block
+		 * twice, because it contains both the oldest and the newest
+		 * data in this window.
+		 *
+		 * First time (wrap_count==2), in the very beginning, to collect
+		 * the oldest data, which is in the range
+		 * (data_bytes..DATA_IN_PAGE).
+		 *
+		 * Second time (wrap_count==1), it's just like any other block,
+		 * containing data in the range of [MSC_BDESC..data_bytes].
+		 */
+		if (iter->block == iter->start_block && iter->wrap_count == 2) {
+			tocopy = DATA_IN_PAGE - data_bytes;
+			src += data_bytes;
+		}
+
+		if (!tocopy)
+			goto next_block;
+
+		tocopy -= iter->block_off;
+		src += iter->block_off;
+
+		if (len < tocopy) {
+			tocopy = len;
+			advance = 0;
+		}
+
+		remaining = fn(data, src, tocopy);
+
+		if (remaining)
+			advance = 0;
+
+		copied = tocopy - remaining;
+		len -= copied;
+		iter->block_off += copied;
+		iter->offset += copied;
+
+		if (!advance)
+			break;
+
+next_block:
+		if (msc_iter_block_advance(iter))
+			break;
+
+	} while (len);
+
+	return size - len;
+}
+
+/**
+ * msc_buffer_clear_hw_header() - clear hw header for multiblock
+ * @msc:	MSC device
+ */
+static void msc_buffer_clear_hw_header(struct msc *msc)
+{
+	struct msc_window *win;
+	struct scatterlist *sg;
+
+	list_for_each_entry(win, &msc->win_list, entry) {
+		unsigned int blk;
+
+		for_each_sg(win->sgt->sgl, sg, win->nr_segs, blk) {
+			struct msc_block_desc *bdesc = sg_virt(sg);
+
+			memset_startat(bdesc, 0, hw_tag);
+		}
+	}
+}
+
+static int intel_th_msu_init(struct msc *msc)
+{
+	u32 mintctl, msusts;
+
+	if (!msc->do_irq)
+		return 0;
+
+	if (!msc->mbuf)
+		return 0;
+
+	mintctl = ioread32(msc->msu_base + REG_MSU_MINTCTL);
+	mintctl |= msc->index ? M1BLIE : M0BLIE;
+	iowrite32(mintctl, msc->msu_base + REG_MSU_MINTCTL);
+	if (mintctl != ioread32(msc->msu_base + REG_MSU_MINTCTL)) {
+		dev_info(msc_dev(msc), "MINTCTL ignores writes: no usable interrupts\n");
+		msc->do_irq = 0;
+		return 0;
+	}
+
+	msusts = ioread32(msc->msu_base + REG_MSU_MSUSTS);
+	iowrite32(msusts, msc->msu_base + REG_MSU_MSUSTS);
+
+	return 0;
+}
+
+static void intel_th_msu_deinit(struct msc *msc)
+{
+	u32 mintctl;
+
+	if (!msc->do_irq)
+		return;
+
+	mintctl = ioread32(msc->msu_base + REG_MSU_MINTCTL);
+	mintctl &= msc->index ? ~M1BLIE : ~M0BLIE;
+	iowrite32(mintctl, msc->msu_base + REG_MSU_MINTCTL);
+}
+
+static int msc_win_set_lockout(struct msc_window *win,
+			       enum lockout_state expect,
+			       enum lockout_state new)
+{
+	enum lockout_state old;
+	unsigned long flags;
+	int ret = 0;
+
+	if (!win->msc->mbuf)
+		return 0;
+
+	spin_lock_irqsave(&win->lo_lock, flags);
+	old = win->lockout;
+
+	if (old != expect) {
+		ret = -EINVAL;
+		goto unlock;
+	}
+
+	win->lockout = new;
+
+	if (old == expect && new == WIN_LOCKED)
+		atomic_inc(&win->msc->user_count);
+	else if (old == expect && old == WIN_LOCKED)
+		atomic_dec(&win->msc->user_count);
+
+unlock:
+	spin_unlock_irqrestore(&win->lo_lock, flags);
+
+	if (ret) {
+		if (expect == WIN_READY && old == WIN_LOCKED)
+			return -EBUSY;
+
+		/* from intel_th_msc_window_unlock(), don't warn if not locked */
+		if (expect == WIN_LOCKED && old == new)
+			return 0;
+
+		dev_warn_ratelimited(msc_dev(win->msc),
+				     "expected lockout state %d, got %d\n",
+				     expect, old);
+	}
+
+	return ret;
+}
+/**
+ * msc_configure() - set up MSC hardware
+ * @msc:	the MSC device to configure
+ *
+ * Program storage mode, wrapping, burst length and trace buffer address
+ * into a given MSC. Then, enable tracing and set msc::enabled.
+ * The latter is serialized on msc::buf_mutex, so make sure to hold it.
+ */
+static int msc_configure(struct msc *msc)
+{
+	u32 reg;
+
+	lockdep_assert_held(&msc->buf_mutex);
+
+	if (msc->mode > MSC_MODE_MULTI)
+		return -EINVAL;
+
+	if (msc->mode == MSC_MODE_MULTI) {
+		if (msc_win_set_lockout(msc->cur_win, WIN_READY, WIN_INUSE))
+			return -EBUSY;
+
+		msc_buffer_clear_hw_header(msc);
+	}
+
+	msc->orig_addr = ioread32(msc->reg_base + REG_MSU_MSC0BAR);
+	msc->orig_sz   = ioread32(msc->reg_base + REG_MSU_MSC0SIZE);
+
+	reg = msc->base_addr >> PAGE_SHIFT;
+	iowrite32(reg, msc->reg_base + REG_MSU_MSC0BAR);
+
+	if (msc->mode == MSC_MODE_SINGLE) {
+		reg = msc->nr_pages;
+		iowrite32(reg, msc->reg_base + REG_MSU_MSC0SIZE);
+	}
+
+	reg = ioread32(msc->reg_base + REG_MSU_MSC0CTL);
+	reg &= ~(MSC_MODE | MSC_WRAPEN | MSC_EN | MSC_RD_HDR_OVRD);
+
+	reg |= MSC_EN;
+	reg |= msc->mode << __ffs(MSC_MODE);
+	reg |= msc->burst_len << __ffs(MSC_LEN);
+
+	if (msc->wrap)
+		reg |= MSC_WRAPEN;
+
+	iowrite32(reg, msc->reg_base + REG_MSU_MSC0CTL);
+
+	intel_th_msu_init(msc);
+
+	msc->thdev->output.multiblock = msc->mode == MSC_MODE_MULTI;
+	intel_th_trace_enable(msc->thdev);
+	msc->enabled = 1;
+
+	if (msc->mbuf && msc->mbuf->activate)
+		msc->mbuf->activate(msc->mbuf_priv);
+
+	return 0;
+}
+
+/**
+ * msc_disable() - disable MSC hardware
+ * @msc:	MSC device to disable
+ *
+ * If @msc is enabled, disable tracing on the switch and then disable MSC
+ * storage. Caller must hold msc::buf_mutex.
+ */
+static void msc_disable(struct msc *msc)
+{
+	struct msc_window *win = msc->cur_win;
+	u32 reg;
+
+	lockdep_assert_held(&msc->buf_mutex);
+
+	if (msc->mode == MSC_MODE_MULTI)
+		msc_win_set_lockout(win, WIN_INUSE, WIN_LOCKED);
+
+	if (msc->mbuf && msc->mbuf->deactivate)
+		msc->mbuf->deactivate(msc->mbuf_priv);
+	intel_th_msu_deinit(msc);
+	intel_th_trace_disable(msc->thdev);
+
+	if (msc->mode == MSC_MODE_SINGLE) {
+		reg = ioread32(msc->reg_base + REG_MSU_MSC0STS);
+		msc->single_wrap = !!(reg & MSCSTS_WRAPSTAT);
+
+		reg = ioread32(msc->reg_base + REG_MSU_MSC0MWP);
+		msc->single_sz = reg & ((msc->nr_pages << PAGE_SHIFT) - 1);
+		dev_dbg(msc_dev(msc), "MSCnMWP: %08x/%08lx, wrap: %d\n",
+			reg, msc->single_sz, msc->single_wrap);
+	}
+
+	reg = ioread32(msc->reg_base + REG_MSU_MSC0CTL);
+	reg &= ~MSC_EN;
+	iowrite32(reg, msc->reg_base + REG_MSU_MSC0CTL);
+
+	if (msc->mbuf && msc->mbuf->ready)
+		msc->mbuf->ready(msc->mbuf_priv, win->sgt,
+				 msc_win_total_sz(win));
+
+	msc->enabled = 0;
+
+	iowrite32(msc->orig_addr, msc->reg_base + REG_MSU_MSC0BAR);
+	iowrite32(msc->orig_sz, msc->reg_base + REG_MSU_MSC0SIZE);
+
+	dev_dbg(msc_dev(msc), "MSCnNWSA: %08x\n",
+		ioread32(msc->reg_base + REG_MSU_MSC0NWSA));
+
+	reg = ioread32(msc->reg_base + REG_MSU_MSC0STS);
+	dev_dbg(msc_dev(msc), "MSCnSTS: %08x\n", reg);
+
+	reg = ioread32(msc->reg_base + REG_MSU_MSUSTS);
+	reg &= msc->index ? MSUSTS_MSC1BLAST : MSUSTS_MSC0BLAST;
+	iowrite32(reg, msc->reg_base + REG_MSU_MSUSTS);
+}
+
+static int intel_th_msc_activate(struct intel_th_device *thdev)
+{
+	struct msc *msc = dev_get_drvdata(&thdev->dev);
+	int ret = -EBUSY;
+
+	if (!atomic_inc_unless_negative(&msc->user_count))
+		return -ENODEV;
+
+	mutex_lock(&msc->buf_mutex);
+
+	/* if there are readers, refuse */
+	if (list_empty(&msc->iter_list))
+		ret = msc_configure(msc);
+
+	mutex_unlock(&msc->buf_mutex);
+
+	if (ret)
+		atomic_dec(&msc->user_count);
+
+	return ret;
+}
+
+static void intel_th_msc_deactivate(struct intel_th_device *thdev)
+{
+	struct msc *msc = dev_get_drvdata(&thdev->dev);
+
+	mutex_lock(&msc->buf_mutex);
+	if (msc->enabled) {
+		msc_disable(msc);
+		atomic_dec(&msc->user_count);
+	}
+	mutex_unlock(&msc->buf_mutex);
+}
+
+/**
+ * msc_buffer_contig_alloc() - allocate a contiguous buffer for SINGLE mode
+ * @msc:	MSC device
+ * @size:	allocation size in bytes
+ *
+ * This modifies msc::base, which requires msc::buf_mutex to serialize, so the
+ * caller is expected to hold it.
+ *
+ * Return:	0 on success, -errno otherwise.
+ */
+static int msc_buffer_contig_alloc(struct msc *msc, unsigned long size)
+{
+	unsigned long nr_pages = size >> PAGE_SHIFT;
+	unsigned int order = get_order(size);
+	struct page *page;
+	int ret;
+
+	if (!size)
+		return 0;
+
+	ret = sg_alloc_table(&msc->single_sgt, 1, GFP_KERNEL);
+	if (ret)
+		goto err_out;
+
+	ret = -ENOMEM;
+	page = alloc_pages(GFP_KERNEL | __GFP_ZERO | GFP_DMA32, order);
+	if (!page)
+		goto err_free_sgt;
+
+	split_page(page, order);
+	sg_set_buf(msc->single_sgt.sgl, page_address(page), size);
+
+	ret = dma_map_sg(msc_dev(msc)->parent->parent, msc->single_sgt.sgl, 1,
+			 DMA_FROM_DEVICE);
+	if (ret < 0)
+		goto err_free_pages;
+
+	msc->nr_pages = nr_pages;
+	msc->base = page_address(page);
+	msc->base_addr = sg_dma_address(msc->single_sgt.sgl);
+
+	return 0;
+
+err_free_pages:
+	__free_pages(page, order);
+
+err_free_sgt:
+	sg_free_table(&msc->single_sgt);
+
+err_out:
+	return ret;
+}
+
+/**
+ * msc_buffer_contig_free() - free a contiguous buffer
+ * @msc:	MSC configured in SINGLE mode
+ */
+static void msc_buffer_contig_free(struct msc *msc)
+{
+	unsigned long off;
+
+	dma_unmap_sg(msc_dev(msc)->parent->parent, msc->single_sgt.sgl,
+		     1, DMA_FROM_DEVICE);
+	sg_free_table(&msc->single_sgt);
+
+	for (off = 0; off < msc->nr_pages << PAGE_SHIFT; off += PAGE_SIZE) {
+		struct page *page = virt_to_page(msc->base + off);
+
+		page->mapping = NULL;
+		__free_page(page);
+	}
+
+	msc->nr_pages = 0;
+}
+
+/**
+ * msc_buffer_contig_get_page() - find a page at a given offset
+ * @msc:	MSC configured in SINGLE mode
+ * @pgoff:	page offset
+ *
+ * Return:	page, if @pgoff is within the range, NULL otherwise.
+ */
+static struct page *msc_buffer_contig_get_page(struct msc *msc,
+					       unsigned long pgoff)
+{
+	if (pgoff >= msc->nr_pages)
+		return NULL;
+
+	return virt_to_page(msc->base + (pgoff << PAGE_SHIFT));
+}
+
+static int __msc_buffer_win_alloc(struct msc_window *win,
+				  unsigned int nr_segs)
+{
+	struct scatterlist *sg_ptr;
+	void *block;
+	int i, ret;
+
+	ret = sg_alloc_table(win->sgt, nr_segs, GFP_KERNEL);
+	if (ret)
+		return -ENOMEM;
+
+	for_each_sg(win->sgt->sgl, sg_ptr, nr_segs, i) {
+		block = dma_alloc_coherent(msc_dev(win->msc)->parent->parent,
+					  PAGE_SIZE, &sg_dma_address(sg_ptr),
+					  GFP_KERNEL);
+		if (!block)
+			goto err_nomem;
+
+		sg_set_buf(sg_ptr, block, PAGE_SIZE);
+	}
+
+	return nr_segs;
+
+err_nomem:
+	for_each_sg(win->sgt->sgl, sg_ptr, i, ret)
+		dma_free_coherent(msc_dev(win->msc)->parent->parent, PAGE_SIZE,
+				  sg_virt(sg_ptr), sg_dma_address(sg_ptr));
+
+	sg_free_table(win->sgt);
+
+	return -ENOMEM;
+}
+
+#ifdef CONFIG_X86
+static void msc_buffer_set_uc(struct msc *msc)
+{
+	struct scatterlist *sg_ptr;
+	struct msc_window *win;
+	int i;
+
+	if (msc->mode == MSC_MODE_SINGLE) {
+		set_memory_uc((unsigned long)msc->base, msc->nr_pages);
+		return;
+	}
+
+	list_for_each_entry(win, &msc->win_list, entry) {
+		for_each_sg(win->sgt->sgl, sg_ptr, win->nr_segs, i) {
+			/* Set the page as uncached */
+			set_memory_uc((unsigned long)sg_virt(sg_ptr),
+					PFN_DOWN(sg_ptr->length));
+		}
+	}
+}
+
+static void msc_buffer_set_wb(struct msc *msc)
+{
+	struct scatterlist *sg_ptr;
+	struct msc_window *win;
+	int i;
+
+	if (msc->mode == MSC_MODE_SINGLE) {
+		set_memory_wb((unsigned long)msc->base, msc->nr_pages);
+		return;
+	}
+
+	list_for_each_entry(win, &msc->win_list, entry) {
+		for_each_sg(win->sgt->sgl, sg_ptr, win->nr_segs, i) {
+			/* Reset the page to write-back */
+			set_memory_wb((unsigned long)sg_virt(sg_ptr),
+					PFN_DOWN(sg_ptr->length));
+		}
+	}
+}
+#else /* !X86 */
+static inline void
+msc_buffer_set_uc(struct msc *msc) {}
+static inline void msc_buffer_set_wb(struct msc *msc) {}
+#endif /* CONFIG_X86 */
+
+static struct page *msc_sg_page(struct scatterlist *sg)
+{
+	void *addr = sg_virt(sg);
+
+	if (is_vmalloc_addr(addr))
+		return vmalloc_to_page(addr);
+
+	return sg_page(sg);
+}
+
+/**
+ * msc_buffer_win_alloc() - alloc a window for a multiblock mode
+ * @msc:	MSC device
+ * @nr_blocks:	number of pages in this window
+ *
+ * This modifies msc::win_list and msc::base, which requires msc::buf_mutex
+ * to serialize, so the caller is expected to hold it.
+ *
+ * Return:	0 on success, -errno otherwise.
+ */
+static int msc_buffer_win_alloc(struct msc *msc, unsigned int nr_blocks)
+{
+	struct msc_window *win;
+	int ret = -ENOMEM;
+
+	if (!nr_blocks)
+		return 0;
+
+	win = kzalloc(sizeof(*win), GFP_KERNEL);
+	if (!win)
+		return -ENOMEM;
+
+	win->msc = msc;
+	win->sgt = &win->_sgt;
+	win->lockout = WIN_READY;
+	spin_lock_init(&win->lo_lock);
+
+	if (!list_empty(&msc->win_list)) {
+		struct msc_window *prev = list_last_entry(&msc->win_list,
+							  struct msc_window,
+							  entry);
+
+		win->pgoff = prev->pgoff + prev->nr_blocks;
+	}
+
+	if (msc->mbuf && msc->mbuf->alloc_window)
+		ret = msc->mbuf->alloc_window(msc->mbuf_priv, &win->sgt,
+					      nr_blocks << PAGE_SHIFT);
+	else
+		ret = __msc_buffer_win_alloc(win, nr_blocks);
+
+	if (ret <= 0)
+		goto err_nomem;
+
+	win->nr_segs = ret;
+	win->nr_blocks = nr_blocks;
+
+	if (list_empty(&msc->win_list)) {
+		msc->base = msc_win_base(win);
+		msc->base_addr = msc_win_base_dma(win);
+		msc->cur_win = win;
+	}
+
+	list_add_tail(&win->entry, &msc->win_list);
+	msc->nr_pages += nr_blocks;
+
+	return 0;
+
+err_nomem:
+	kfree(win);
+
+	return ret;
+}
+
+static void __msc_buffer_win_free(struct msc *msc, struct msc_window *win)
+{
+	struct scatterlist *sg;
+	int i;
+
+	for_each_sg(win->sgt->sgl, sg, win->nr_segs, i) {
+		struct page *page = msc_sg_page(sg);
+
+		page->mapping = NULL;
+		dma_free_coherent(msc_dev(win->msc)->parent->parent, PAGE_SIZE,
+				  sg_virt(sg), sg_dma_address(sg));
+	}
+	sg_free_table(win->sgt);
+}
+
+/**
+ * msc_buffer_win_free() - free a window from MSC's window list
+ * @msc:	MSC device
+ * @win:	window to free
+ *
+ * This modifies msc::win_list and msc::base, which requires msc::buf_mutex
+ * to serialize, so the caller is expected to hold it.
+ */
+static void msc_buffer_win_free(struct msc *msc, struct msc_window *win)
+{
+	msc->nr_pages -= win->nr_blocks;
+
+	list_del(&win->entry);
+	if (list_empty(&msc->win_list)) {
+		msc->base = NULL;
+		msc->base_addr = 0;
+	}
+
+	if (msc->mbuf && msc->mbuf->free_window)
+		msc->mbuf->free_window(msc->mbuf_priv, win->sgt);
+	else
+		__msc_buffer_win_free(msc, win);
+
+	kfree(win);
+}
+
+/**
+ * msc_buffer_relink() - set up block descriptors for multiblock mode
+ * @msc:	MSC device
+ *
+ * This traverses msc::win_list, which requires msc::buf_mutex to serialize,
+ * so the caller is expected to hold it.
+ */
+static void msc_buffer_relink(struct msc *msc)
+{
+	struct msc_window *win, *next_win;
+
+	/* call with msc::mutex locked */
+	list_for_each_entry(win, &msc->win_list, entry) {
+		struct scatterlist *sg;
+		unsigned int blk;
+		u32 sw_tag = 0;
+
+		/*
+		 * Last window's next_win should point to the first window
+		 * and MSC_SW_TAG_LASTWIN should be set.
+		 */
+		if (msc_is_last_win(win)) {
+			sw_tag |= MSC_SW_TAG_LASTWIN;
+			next_win = list_first_entry(&msc->win_list,
+						    struct msc_window, entry);
+		} else {
+			next_win = list_next_entry(win, entry);
+		}
+
+		for_each_sg(win->sgt->sgl, sg, win->nr_segs, blk) {
+			struct msc_block_desc *bdesc = sg_virt(sg);
+
+			memset(bdesc, 0, sizeof(*bdesc));
+
+			bdesc->next_win = msc_win_base_pfn(next_win);
+
+			/*
+			 * Similarly to last window, last block should point
+			 * to the first one.
+			 */
+			if (blk == win->nr_segs - 1) {
+				sw_tag |= MSC_SW_TAG_LASTBLK;
+				bdesc->next_blk = msc_win_base_pfn(win);
+			} else {
+				dma_addr_t addr = sg_dma_address(sg_next(sg));
+
+				bdesc->next_blk = PFN_DOWN(addr);
+			}
+
+			bdesc->sw_tag = sw_tag;
+			bdesc->block_sz = sg->length / 64;
+		}
+	}
+
+	/*
+	 * Make the above writes globally visible before tracing is
+	 * enabled to make sure hardware sees them coherently.
+	 */
+	wmb();
+}
+
+static void msc_buffer_multi_free(struct msc *msc)
+{
+	struct msc_window *win, *iter;
+
+	list_for_each_entry_safe(win, iter, &msc->win_list, entry)
+		msc_buffer_win_free(msc, win);
+}
+
+static int msc_buffer_multi_alloc(struct msc *msc, unsigned long *nr_pages,
+				  unsigned int nr_wins)
+{
+	int ret, i;
+
+	for (i = 0; i < nr_wins; i++) {
+		ret = msc_buffer_win_alloc(msc, nr_pages[i]);
+		if (ret) {
+			msc_buffer_multi_free(msc);
+			return ret;
+		}
+	}
+
+	msc_buffer_relink(msc);
+
+	return 0;
+}
+
+/**
+ * msc_buffer_free() - free buffers for MSC
+ * @msc:	MSC device
+ *
+ * Free MSC's storage buffers.
+ *
+ * This modifies msc::win_list and msc::base, which requires msc::buf_mutex to
+ * serialize, so the caller is expected to hold it.
+ */
+static void msc_buffer_free(struct msc *msc)
+{
+	msc_buffer_set_wb(msc);
+
+	if (msc->mode == MSC_MODE_SINGLE)
+		msc_buffer_contig_free(msc);
+	else if (msc->mode == MSC_MODE_MULTI)
+		msc_buffer_multi_free(msc);
+}
+
+/**
+ * msc_buffer_alloc() - allocate a buffer for MSC
+ * @msc:	MSC device
+ * @size:	allocation size in bytes
+ *
+ * Allocate a storage buffer for MSC, depending on the msc::mode, it will be
+ * either done via msc_buffer_contig_alloc() for SINGLE operation mode or
+ * msc_buffer_win_alloc() for multiblock operation. The latter allocates one
+ * window per invocation, so in multiblock mode this can be called multiple
+ * times for the same MSC to allocate multiple windows.
+ *
+ * This modifies msc::win_list and msc::base, which requires msc::buf_mutex
+ * to serialize, so the caller is expected to hold it.
+ *
+ * Return:	0 on success, -errno otherwise.
+ */
+static int msc_buffer_alloc(struct msc *msc, unsigned long *nr_pages,
+			    unsigned int nr_wins)
+{
+	int ret;
+
+	/* -1: buffer not allocated */
+	if (atomic_read(&msc->user_count) != -1)
+		return -EBUSY;
+
+	if (msc->mode == MSC_MODE_SINGLE) {
+		if (nr_wins != 1)
+			return -EINVAL;
+
+		ret = msc_buffer_contig_alloc(msc, nr_pages[0] << PAGE_SHIFT);
+	} else if (msc->mode == MSC_MODE_MULTI) {
+		ret = msc_buffer_multi_alloc(msc, nr_pages, nr_wins);
+	} else {
+		ret = -EINVAL;
+	}
+
+	if (!ret) {
+		msc_buffer_set_uc(msc);
+
+		/* allocation should be visible before the counter goes to 0 */
+		smp_mb__before_atomic();
+
+		if (WARN_ON_ONCE(atomic_cmpxchg(&msc->user_count, -1, 0) != -1))
+			return -EINVAL;
+	}
+
+	return ret;
+}
+
+/**
+ * msc_buffer_unlocked_free_unless_used() - free a buffer unless it's in use
+ * @msc:	MSC device
+ *
+ * This will free MSC buffer unless it is in use or there is no allocated
+ * buffer.
+ * Caller needs to hold msc::buf_mutex.
+ *
+ * Return:	0 on successful deallocation or if there was no buffer to
+ *		deallocate, -EBUSY if there are active users.
+ */
+static int msc_buffer_unlocked_free_unless_used(struct msc *msc)
+{
+	int count, ret = 0;
+
+	count = atomic_cmpxchg(&msc->user_count, 0, -1);
+
+	/* > 0: buffer is allocated and has users */
+	if (count > 0)
+		ret = -EBUSY;
+	/* 0: buffer is allocated, no users */
+	else if (!count)
+		msc_buffer_free(msc);
+	/* < 0: no buffer, nothing to do */
+
+	return ret;
+}
+
+/**
+ * msc_buffer_free_unless_used() - free a buffer unless it's in use
+ * @msc:	MSC device
+ *
+ * This is a locked version of msc_buffer_unlocked_free_unless_used().
+ */
+static int msc_buffer_free_unless_used(struct msc *msc)
+{
+	int ret;
+
+	mutex_lock(&msc->buf_mutex);
+	ret = msc_buffer_unlocked_free_unless_used(msc);
+	mutex_unlock(&msc->buf_mutex);
+
+	return ret;
+}
+
+/**
+ * msc_buffer_get_page() - get MSC buffer page at a given offset
+ * @msc:	MSC device
+ * @pgoff:	page offset into the storage buffer
+ *
+ * This traverses msc::win_list, so holding msc::buf_mutex is expected from
+ * the caller.
+ *
+ * Return:	page if @pgoff corresponds to a valid buffer page or NULL.
+ */
+static struct page *msc_buffer_get_page(struct msc *msc, unsigned long pgoff)
+{
+	struct msc_window *win;
+	struct scatterlist *sg;
+	unsigned int blk;
+
+	if (msc->mode == MSC_MODE_SINGLE)
+		return msc_buffer_contig_get_page(msc, pgoff);
+
+	list_for_each_entry(win, &msc->win_list, entry)
+		if (pgoff >= win->pgoff && pgoff < win->pgoff + win->nr_blocks)
+			goto found;
+
+	return NULL;
+
+found:
+	pgoff -= win->pgoff;
+
+	for_each_sg(win->sgt->sgl, sg, win->nr_segs, blk) {
+		struct page *page = msc_sg_page(sg);
+		size_t pgsz = PFN_DOWN(sg->length);
+
+		if (pgoff < pgsz)
+			return page + pgoff;
+
+		pgoff -= pgsz;
+	}
+
+	return NULL;
+}
+
+/**
+ * struct msc_win_to_user_struct - data for copy_to_user() callback
+ * @buf:	userspace buffer to copy data to
+ * @offset:	running offset
+ */
+struct msc_win_to_user_struct {
+	char __user	*buf;
+	unsigned long	offset;
+};
+
+/**
+ * msc_win_to_user() - iterator for msc_buffer_iterate() to copy data to user
+ * @data:	callback's private data
+ * @src:	source buffer
+ * @len:	amount of data to copy from the source buffer
+ */
+static unsigned long msc_win_to_user(void *data, void *src, size_t len)
+{
+	struct msc_win_to_user_struct *u = data;
+	unsigned long ret;
+
+	ret = copy_to_user(u->buf + u->offset, src, len);
+	u->offset += len - ret;
+
+	return ret;
+}
+
+
+/*
+ * file operations' callbacks
+ */
+
+static int intel_th_msc_open(struct inode *inode, struct file *file)
+{
+	struct intel_th_device *thdev = file->private_data;
+	struct msc *msc = dev_get_drvdata(&thdev->dev);
+	struct msc_iter *iter;
+
+	if (!capable(CAP_SYS_RAWIO))
+		return -EPERM;
+
+	iter = msc_iter_install(msc);
+	if (IS_ERR(iter))
+		return PTR_ERR(iter);
+
+	file->private_data = iter;
+
+	return nonseekable_open(inode, file);
+}
+
+static int intel_th_msc_release(struct inode *inode, struct file *file)
+{
+	struct msc_iter *iter = file->private_data;
+	struct msc *msc = iter->msc;
+
+	msc_iter_remove(iter, msc);
+
+	return 0;
+}
+
+static ssize_t
+msc_single_to_user(struct msc *msc, char __user *buf, loff_t off, size_t len)
+{
+	unsigned long size = msc->nr_pages << PAGE_SHIFT, rem = len;
+	unsigned long start = off, tocopy = 0;
+
+	if (msc->single_wrap) {
+		start += msc->single_sz;
+		if (start < size) {
+			tocopy = min(rem, size - start);
+			if (copy_to_user(buf, msc->base + start, tocopy))
+				return -EFAULT;
+
+			buf += tocopy;
+			rem -= tocopy;
+			start += tocopy;
+		}
+
+		start &= size - 1;
+		if (rem) {
+			tocopy = min(rem, msc->single_sz - start);
+			if (copy_to_user(buf, msc->base + start, tocopy))
+				return -EFAULT;
+
+			rem -= tocopy;
+		}
+
+		return len - rem;
+	}
+
+	if (copy_to_user(buf, msc->base + start, rem))
+		return -EFAULT;
+
+	return len;
+}
+
+static ssize_t intel_th_msc_read(struct file *file, char __user *buf,
+				 size_t len, loff_t *ppos)
+{
+	struct msc_iter *iter = file->private_data;
+	struct msc *msc = iter->msc;
+	size_t size;
+	loff_t off = *ppos;
+	ssize_t ret = 0;
+
+	if (!atomic_inc_unless_negative(&msc->user_count))
+		return 0;
+
+	if (msc->mode == MSC_MODE_SINGLE && !msc->single_wrap)
+		size = msc->single_sz;
+	else
+		size = msc->nr_pages << PAGE_SHIFT;
+
+	if (!size)
+		goto put_count;
+
+	if (off >= size)
+		goto put_count;
+
+	if (off + len >= size)
+		len = size - off;
+
+	if (msc->mode == MSC_MODE_SINGLE) {
+		ret = msc_single_to_user(msc, buf, off, len);
+		if (ret >= 0)
+			*ppos += ret;
+	} else if (msc->mode == MSC_MODE_MULTI) {
+		struct msc_win_to_user_struct u = {
+			.buf	= buf,
+			.offset	= 0,
+		};
+
+		ret = msc_buffer_iterate(iter, len, &u, msc_win_to_user);
+		if (ret >= 0)
+			*ppos = iter->offset;
+	} else {
+		ret = -EINVAL;
+	}
+
+put_count:
+	atomic_dec(&msc->user_count);
+
+	return ret;
+}
+
+/*
+ * vm operations callbacks (vm_ops)
+ */
+
+static void msc_mmap_open(struct vm_area_struct *vma)
+{
+	struct msc_iter *iter = vma->vm_file->private_data;
+	struct msc *msc = iter->msc;
+
+	atomic_inc(&msc->mmap_count);
+}
+
+static void msc_mmap_close(struct vm_area_struct *vma)
+{
+	struct msc_iter *iter = vma->vm_file->private_data;
+	struct msc *msc = iter->msc;
+	unsigned long pg;
+
+	if (!atomic_dec_and_mutex_lock(&msc->mmap_count, &msc->buf_mutex))
+		return;
+
+	/* drop page _refcounts */
+	for (pg = 0; pg < msc->nr_pages; pg++) {
+		struct page *page = msc_buffer_get_page(msc, pg);
+
+		if (WARN_ON_ONCE(!page))
+			continue;
+
+		if (page->mapping)
+			page->mapping = NULL;
+	}
+
+	/* last mapping -- drop user_count */
+	atomic_dec(&msc->user_count);
+	mutex_unlock(&msc->buf_mutex);
+}
+
+static vm_fault_t msc_mmap_fault(struct vm_fault *vmf)
+{
+	struct msc_iter *iter = vmf->vma->vm_file->private_data;
+	struct msc *msc = iter->msc;
+
+	vmf->page = msc_buffer_get_page(msc, vmf->pgoff);
+	if (!vmf->page)
+		return VM_FAULT_SIGBUS;
+
+	get_page(vmf->page);
+	vmf->page->mapping = vmf->vma->vm_file->f_mapping;
+	vmf->page->index = vmf->pgoff;
+
+	return 0;
+}
+
+static const struct vm_operations_struct msc_mmap_ops = {
+	.open	= msc_mmap_open,
+	.close	= msc_mmap_close,
+	.fault	= msc_mmap_fault,
+};
+
+static int intel_th_msc_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	unsigned long size = vma->vm_end - vma->vm_start;
+	struct msc_iter *iter = vma->vm_file->private_data;
+	struct msc *msc = iter->msc;
+	int ret = -EINVAL;
+
+	if (!size || offset_in_page(size))
+		return -EINVAL;
+
+	if (vma->vm_pgoff)
+		return -EINVAL;
+
+	/* grab user_count once per mmap; drop in msc_mmap_close() */
+	if (!atomic_inc_unless_negative(&msc->user_count))
+		return -EINVAL;
+
+	if (msc->mode != MSC_MODE_SINGLE &&
+	    msc->mode != MSC_MODE_MULTI)
+		goto out;
+
+	if (size >> PAGE_SHIFT != msc->nr_pages)
+		goto out;
+
+	atomic_set(&msc->mmap_count, 1);
+	ret = 0;
+
+out:
+	if (ret)
+		atomic_dec(&msc->user_count);
+
+	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+	vma->vm_flags |= VM_DONTEXPAND | VM_DONTCOPY;
+	vma->vm_ops = &msc_mmap_ops;
+	return ret;
+}
+
+static const struct file_operations intel_th_msc_fops = {
+	.open		= intel_th_msc_open,
+	.release	= intel_th_msc_release,
+	.read		= intel_th_msc_read,
+	.mmap		= intel_th_msc_mmap,
+	.llseek		= no_llseek,
+	.owner		= THIS_MODULE,
+};
+
+static void intel_th_msc_wait_empty(struct intel_th_device *thdev)
+{
+	struct msc *msc = dev_get_drvdata(&thdev->dev);
+	unsigned long count;
+	u32 reg;
+
+	for (reg = 0, count = MSC_PLE_WAITLOOP_DEPTH;
+	     count && !(reg & MSCSTS_PLE); count--) {
+		reg = __raw_readl(msc->reg_base + REG_MSU_MSC0STS);
+		cpu_relax();
+	}
+
+	if (!count)
+		dev_dbg(msc_dev(msc), "timeout waiting for MSC0 PLE\n");
+}
+
+static int intel_th_msc_init(struct msc *msc)
+{
+	atomic_set(&msc->user_count, -1);
+
+	msc->mode = msc->multi_is_broken ? MSC_MODE_SINGLE : MSC_MODE_MULTI;
+	mutex_init(&msc->buf_mutex);
+	INIT_LIST_HEAD(&msc->win_list);
+	INIT_LIST_HEAD(&msc->iter_list);
+
+	msc->burst_len =
+		(ioread32(msc->reg_base + REG_MSU_MSC0CTL) & MSC_LEN) >>
+		__ffs(MSC_LEN);
+
+	return 0;
+}
+
+static int msc_win_switch(struct msc *msc)
+{
+	struct msc_window *first;
+
+	if (list_empty(&msc->win_list))
+		return -EINVAL;
+
+	first = list_first_entry(&msc->win_list, struct msc_window, entry);
+
+	if (msc_is_last_win(msc->cur_win))
+		msc->cur_win = first;
+	else
+		msc->cur_win = list_next_entry(msc->cur_win, entry);
+
+	msc->base = msc_win_base(msc->cur_win);
+	msc->base_addr = msc_win_base_dma(msc->cur_win);
+
+	intel_th_trace_switch(msc->thdev);
+
+	return 0;
+}
+
+/**
+ * intel_th_msc_window_unlock - put the window back in rotation
+ * @dev:	MSC device to which this relates
+ * @sgt:	buffer's sg_table for the window, does nothing if NULL
+ */
+void intel_th_msc_window_unlock(struct device *dev, struct sg_table *sgt)
+{
+	struct msc *msc = dev_get_drvdata(dev);
+	struct msc_window *win;
+
+	if (!sgt)
+		return;
+
+	win = msc_find_window(msc, sgt, false);
+	if (!win)
+		return;
+
+	msc_win_set_lockout(win, WIN_LOCKED, WIN_READY);
+	if (msc->switch_on_unlock == win) {
+		msc->switch_on_unlock = NULL;
+		msc_win_switch(msc);
+	}
+}
+EXPORT_SYMBOL_GPL(intel_th_msc_window_unlock);
+
+static void msc_work(struct work_struct *work)
+{
+	struct msc *msc = container_of(work, struct msc, work);
+
+	intel_th_msc_deactivate(msc->thdev);
+}
+
+static irqreturn_t intel_th_msc_interrupt(struct intel_th_device *thdev)
+{
+	struct msc *msc = dev_get_drvdata(&thdev->dev);
+	u32 msusts = ioread32(msc->msu_base + REG_MSU_MSUSTS);
+	u32 mask = msc->index ? MSUSTS_MSC1BLAST : MSUSTS_MSC0BLAST;
+	struct msc_window *win, *next_win;
+
+	if (!msc->do_irq || !msc->mbuf)
+		return IRQ_NONE;
+
+	msusts &= mask;
+
+	if (!msusts)
+		return msc->enabled ? IRQ_HANDLED : IRQ_NONE;
+
+	iowrite32(msusts, msc->msu_base + REG_MSU_MSUSTS);
+
+	if (!msc->enabled)
+		return IRQ_NONE;
+
+	/* grab the window before we do the switch */
+	win = msc->cur_win;
+	if (!win)
+		return IRQ_HANDLED;
+	next_win = msc_next_window(win);
+	if (!next_win)
+		return IRQ_HANDLED;
+
+	/* next window: if READY, proceed, if LOCKED, stop the trace */
+	if (msc_win_set_lockout(next_win, WIN_READY, WIN_INUSE)) {
+		if (msc->stop_on_full)
+			schedule_work(&msc->work);
+		else
+			msc->switch_on_unlock = next_win;
+
+		return IRQ_HANDLED;
+	}
+
+	/* current window: INUSE -> LOCKED */
+	msc_win_set_lockout(win, WIN_INUSE, WIN_LOCKED);
+
+	msc_win_switch(msc);
+
+	if (msc->mbuf && msc->mbuf->ready)
+		msc->mbuf->ready(msc->mbuf_priv, win->sgt,
+				 msc_win_total_sz(win));
+
+	return IRQ_HANDLED;
+}
+
+static const char * const msc_mode[] = {
+	[MSC_MODE_SINGLE]	= "single",
+	[MSC_MODE_MULTI]	= "multi",
+	[MSC_MODE_EXI]		= "ExI",
+	[MSC_MODE_DEBUG]	= "debug",
+};
+
+static ssize_t
+wrap_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct msc *msc = dev_get_drvdata(dev);
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n", msc->wrap);
+}
+
+static ssize_t
+wrap_store(struct device *dev, struct device_attribute *attr, const char *buf,
+	   size_t size)
+{
+	struct msc *msc = dev_get_drvdata(dev);
+	unsigned long val;
+	int ret;
+
+	ret = kstrtoul(buf, 10, &val);
+	if (ret)
+		return ret;
+
+	msc->wrap = !!val;
+
+	return size;
+}
+
+static DEVICE_ATTR_RW(wrap);
+
+static void msc_buffer_unassign(struct msc *msc)
+{
+	lockdep_assert_held(&msc->buf_mutex);
+
+	if (!msc->mbuf)
+		return;
+
+	msc->mbuf->unassign(msc->mbuf_priv);
+	msu_buffer_put(msc->mbuf);
+	msc->mbuf_priv = NULL;
+	msc->mbuf = NULL;
+}
+
+static ssize_t
+mode_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct msc *msc = dev_get_drvdata(dev);
+	const char *mode = msc_mode[msc->mode];
+	ssize_t ret;
+
+	mutex_lock(&msc->buf_mutex);
+	if (msc->mbuf)
+		mode = msc->mbuf->name;
+	ret = scnprintf(buf, PAGE_SIZE, "%s\n", mode);
+	mutex_unlock(&msc->buf_mutex);
+
+	return ret;
+}
+
+static ssize_t
+mode_store(struct device *dev, struct device_attribute *attr, const char *buf,
+	   size_t size)
+{
+	const struct msu_buffer *mbuf = NULL;
+	struct msc *msc = dev_get_drvdata(dev);
+	size_t len = size;
+	char *cp, *mode;
+	int i, ret;
+
+	if (!capable(CAP_SYS_RAWIO))
+		return -EPERM;
+
+	cp = memchr(buf, '\n', len);
+	if (cp)
+		len = cp - buf;
+
+	mode = kstrndup(buf, len, GFP_KERNEL);
+	if (!mode)
+		return -ENOMEM;
+
+	i = match_string(msc_mode, ARRAY_SIZE(msc_mode), mode);
+	if (i >= 0) {
+		kfree(mode);
+		goto found;
+	}
+
+	/* Buffer sinks only work with a usable IRQ */
+	if (!msc->do_irq) {
+		kfree(mode);
+		return -EINVAL;
+	}
+
+	mbuf = msu_buffer_get(mode);
+	kfree(mode);
+	if (mbuf)
+		goto found;
+
+	return -EINVAL;
+
+found:
+	if (i == MSC_MODE_MULTI && msc->multi_is_broken)
+		return -EOPNOTSUPP;
+
+	mutex_lock(&msc->buf_mutex);
+	ret = 0;
+
+	/* Same buffer: do nothing */
+	if (mbuf && mbuf == msc->mbuf) {
+		/* put the extra reference we just got */
+		msu_buffer_put(mbuf);
+		goto unlock;
+	}
+
+	ret = msc_buffer_unlocked_free_unless_used(msc);
+	if (ret)
+		goto unlock;
+
+	if (mbuf) {
+		void *mbuf_priv = mbuf->assign(dev, &i);
+
+		if (!mbuf_priv) {
+			ret = -ENOMEM;
+			goto unlock;
+		}
+
+		msc_buffer_unassign(msc);
+		msc->mbuf_priv = mbuf_priv;
+		msc->mbuf = mbuf;
+	} else {
+		msc_buffer_unassign(msc);
+	}
+
+	msc->mode = i;
+
+unlock:
+	if (ret && mbuf)
+		msu_buffer_put(mbuf);
+	mutex_unlock(&msc->buf_mutex);
+
+	return ret ? ret : size;
+}
+
+static DEVICE_ATTR_RW(mode);
+
+static ssize_t
+nr_pages_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct msc *msc = dev_get_drvdata(dev);
+	struct msc_window *win;
+	size_t count = 0;
+
+	mutex_lock(&msc->buf_mutex);
+
+	if (msc->mode == MSC_MODE_SINGLE)
+		count = scnprintf(buf, PAGE_SIZE, "%ld\n", msc->nr_pages);
+	else if (msc->mode == MSC_MODE_MULTI) {
+		list_for_each_entry(win, &msc->win_list, entry) {
+			count += scnprintf(buf + count, PAGE_SIZE - count,
+					   "%d%c", win->nr_blocks,
+					   msc_is_last_win(win) ? '\n' : ',');
+		}
+	} else {
+		count = scnprintf(buf, PAGE_SIZE, "unsupported\n");
+	}
+
+	mutex_unlock(&msc->buf_mutex);
+
+	return count;
+}
+
+static ssize_t
+nr_pages_store(struct device *dev, struct device_attribute *attr,
+	       const char *buf, size_t size)
+{
+	struct msc *msc = dev_get_drvdata(dev);
+	unsigned long val, *win = NULL, *rewin;
+	size_t len = size;
+	const char *p = buf;
+	char *end, *s;
+	int ret, nr_wins = 0;
+
+	if (!capable(CAP_SYS_RAWIO))
+		return -EPERM;
+
+	ret = msc_buffer_free_unless_used(msc);
+	if (ret)
+		return ret;
+
+	/* scan the comma-separated list of allocation sizes */
+	end = memchr(buf, '\n', len);
+	if (end)
+		len = end - buf;
+
+	do {
+		end = memchr(p, ',', len);
+		s = kstrndup(p, end ? end - p : len, GFP_KERNEL);
+		if (!s) {
+			ret = -ENOMEM;
+			goto free_win;
+		}
+
+		ret = kstrtoul(s, 10, &val);
+		kfree(s);
+
+		if (ret || !val)
+			goto free_win;
+
+		if (nr_wins && msc->mode == MSC_MODE_SINGLE) {
+			ret = -EINVAL;
+			goto free_win;
+		}
+
+		nr_wins++;
+		rewin = krealloc_array(win, nr_wins, sizeof(*win), GFP_KERNEL);
+		if (!rewin) {
+			kfree(win);
+			return -ENOMEM;
+		}
+
+		win = rewin;
+		win[nr_wins - 1] = val;
+
+		if (!end)
+			break;
+
+		/* consume the number and the following comma, hence +1 */
+		len -= end - p + 1;
+		p = end + 1;
+	} while (len);
+
+	mutex_lock(&msc->buf_mutex);
+	ret = msc_buffer_alloc(msc, win, nr_wins);
+	mutex_unlock(&msc->buf_mutex);
+
+free_win:
+	kfree(win);
+
+	return ret ? ret : size;
+}
+
+static DEVICE_ATTR_RW(nr_pages);
+
+static ssize_t
+win_switch_store(struct device *dev, struct device_attribute *attr,
+		 const char *buf, size_t size)
+{
+	struct msc *msc = dev_get_drvdata(dev);
+	unsigned long val;
+	int ret;
+
+	ret = kstrtoul(buf, 10, &val);
+	if (ret)
+		return ret;
+
+	if (val != 1)
+		return -EINVAL;
+
+	ret = -EINVAL;
+	mutex_lock(&msc->buf_mutex);
+	/*
+	 * Window switch can only happen in the "multi" mode.
+	 * If a external buffer is engaged, they have the full
+	 * control over window switching.
+	 */
+	if (msc->mode == MSC_MODE_MULTI && !msc->mbuf)
+		ret = msc_win_switch(msc);
+	mutex_unlock(&msc->buf_mutex);
+
+	return ret ? ret : size;
+}
+
+static DEVICE_ATTR_WO(win_switch);
+
+static ssize_t stop_on_full_show(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	struct msc *msc = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", msc->stop_on_full);
+}
+
+static ssize_t stop_on_full_store(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buf, size_t size)
+{
+	struct msc *msc = dev_get_drvdata(dev);
+	int ret;
+
+	ret = kstrtobool(buf, &msc->stop_on_full);
+	if (ret)
+		return ret;
+
+	return size;
+}
+
+static DEVICE_ATTR_RW(stop_on_full);
+
+static struct attribute *msc_output_attrs[] = {
+	&dev_attr_wrap.attr,
+	&dev_attr_mode.attr,
+	&dev_attr_nr_pages.attr,
+	&dev_attr_win_switch.attr,
+	&dev_attr_stop_on_full.attr,
+	NULL,
+};
+
+static const struct attribute_group msc_output_group = {
+	.attrs	= msc_output_attrs,
+};
+
+static int intel_th_msc_probe(struct intel_th_device *thdev)
+{
+	struct device *dev = &thdev->dev;
+	struct resource *res;
+	struct msc *msc;
+	void __iomem *base;
+	int err;
+
+	res = intel_th_device_get_resource(thdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENODEV;
+
+	base = devm_ioremap(dev, res->start, resource_size(res));
+	if (!base)
+		return -ENOMEM;
+
+	msc = devm_kzalloc(dev, sizeof(*msc), GFP_KERNEL);
+	if (!msc)
+		return -ENOMEM;
+
+	res = intel_th_device_get_resource(thdev, IORESOURCE_IRQ, 1);
+	if (!res)
+		msc->do_irq = 1;
+
+	if (INTEL_TH_CAP(to_intel_th(thdev), multi_is_broken))
+		msc->multi_is_broken = 1;
+
+	msc->index = thdev->id;
+
+	msc->thdev = thdev;
+	msc->reg_base = base + msc->index * 0x100;
+	msc->msu_base = base;
+
+	INIT_WORK(&msc->work, msc_work);
+	err = intel_th_msc_init(msc);
+	if (err)
+		return err;
+
+	dev_set_drvdata(dev, msc);
+
+	return 0;
+}
+
+static void intel_th_msc_remove(struct intel_th_device *thdev)
+{
+	struct msc *msc = dev_get_drvdata(&thdev->dev);
+	int ret;
+
+	intel_th_msc_deactivate(thdev);
+
+	/*
+	 * Buffers should not be used at this point except if the
+	 * output character device is still open and the parent
+	 * device gets detached from its bus, which is a FIXME.
+	 */
+	ret = msc_buffer_free_unless_used(msc);
+	WARN_ON_ONCE(ret);
+}
+
+static struct intel_th_driver intel_th_msc_driver = {
+	.probe	= intel_th_msc_probe,
+	.remove	= intel_th_msc_remove,
+	.irq		= intel_th_msc_interrupt,
+	.wait_empty	= intel_th_msc_wait_empty,
+	.activate	= intel_th_msc_activate,
+	.deactivate	= intel_th_msc_deactivate,
+	.fops	= &intel_th_msc_fops,
+	.attr_group	= &msc_output_group,
+	.driver	= {
+		.name	= "msc",
+		.owner	= THIS_MODULE,
+	},
+};
+
+module_driver(intel_th_msc_driver,
+	      intel_th_driver_register,
+	      intel_th_driver_unregister);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Intel(R) Trace Hub Memory Storage Unit driver");
+MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");