Adding upstream version 6.1.76.upstream/6.1.76

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

1 files changed, 787 insertions, 0 deletions

diff --git a/drivers/net/ipa/gsi_trans.c b/drivers/net/ipa/gsi_trans.c
new file mode 100644
index 000000000..fa6863c26
--- /dev/null
+++ b/drivers/net/ipa/gsi_trans.c
@@ -0,0 +1,787 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/* Copyright (c) 2012-2018, The Linux Foundation. All rights reserved.
+ * Copyright (C) 2019-2022 Linaro Ltd.
+ */
+
+#include <linux/types.h>
+#include <linux/bits.h>
+#include <linux/bitfield.h>
+#include <linux/refcount.h>
+#include <linux/scatterlist.h>
+#include <linux/dma-direction.h>
+
+#include "gsi.h"
+#include "gsi_private.h"
+#include "gsi_trans.h"
+#include "ipa_gsi.h"
+#include "ipa_data.h"
+#include "ipa_cmd.h"
+
+/**
+ * DOC: GSI Transactions
+ *
+ * A GSI transaction abstracts the behavior of a GSI channel by representing
+ * everything about a related group of IPA operations in a single structure.
+ * (A "operation" in this sense is either a data transfer or an IPA immediate
+ * command.)  Most details of interaction with the GSI hardware are managed
+ * by the GSI transaction core, allowing users to simply describe operations
+ * to be performed.  When a transaction has completed a callback function
+ * (dependent on the type of endpoint associated with the channel) allows
+ * cleanup of resources associated with the transaction.
+ *
+ * To perform an operation (or set of them), a user of the GSI transaction
+ * interface allocates a transaction, indicating the number of TREs required
+ * (one per operation).  If sufficient TREs are available, they are reserved
+ * for use in the transaction and the allocation succeeds.  This way
+ * exhaustion of the available TREs in a channel ring is detected as early
+ * as possible.  Any other resources that might be needed to complete a
+ * transaction are also allocated when the transaction is allocated.
+ *
+ * Operations performed as part of a transaction are represented in an array
+ * of Linux scatterlist structures, allocated with the transaction.  These
+ * scatterlist structures are initialized by "adding" operations to the
+ * transaction.  If a buffer in an operation must be mapped for DMA, this is
+ * done at the time it is added to the transaction.  It is possible for a
+ * mapping error to occur when an operation is added.  In this case the
+ * transaction should simply be freed; this correctly releases resources
+ * associated with the transaction.
+ *
+ * Once all operations have been successfully added to a transaction, the
+ * transaction is committed.  Committing transfers ownership of the entire
+ * transaction to the GSI transaction core.  The GSI transaction code
+ * formats the content of the scatterlist array into the channel ring
+ * buffer and informs the hardware that new TREs are available to process.
+ *
+ * The last TRE in each transaction is marked to interrupt the AP when the
+ * GSI hardware has completed it.  Because transfers described by TREs are
+ * performed strictly in order, signaling the completion of just the last
+ * TRE in the transaction is sufficient to indicate the full transaction
+ * is complete.
+ *
+ * When a transaction is complete, ipa_gsi_trans_complete() is called by the
+ * GSI code into the IPA layer, allowing it to perform any final cleanup
+ * required before the transaction is freed.
+ */
+
+/* Hardware values representing a transfer element type */
+enum gsi_tre_type {
+	GSI_RE_XFER	= 0x2,
+	GSI_RE_IMMD_CMD	= 0x3,
+};
+
+/* An entry in a channel ring */
+struct gsi_tre {
+	__le64 addr;		/* DMA address */
+	__le16 len_opcode;	/* length in bytes or enum IPA_CMD_* */
+	__le16 reserved;
+	__le32 flags;		/* TRE_FLAGS_* */
+};
+
+/* gsi_tre->flags mask values (in CPU byte order) */
+#define TRE_FLAGS_CHAIN_FMASK	GENMASK(0, 0)
+#define TRE_FLAGS_IEOT_FMASK	GENMASK(9, 9)
+#define TRE_FLAGS_BEI_FMASK	GENMASK(10, 10)
+#define TRE_FLAGS_TYPE_FMASK	GENMASK(23, 16)
+
+int gsi_trans_pool_init(struct gsi_trans_pool *pool, size_t size, u32 count,
+			u32 max_alloc)
+{
+	void *virt;
+
+	if (!size)
+		return -EINVAL;
+	if (count < max_alloc)
+		return -EINVAL;
+	if (!max_alloc)
+		return -EINVAL;
+
+	/* By allocating a few extra entries in our pool (one less
+	 * than the maximum number that will be requested in a
+	 * single allocation), we can always satisfy requests without
+	 * ever worrying about straddling the end of the pool array.
+	 * If there aren't enough entries starting at the free index,
+	 * we just allocate free entries from the beginning of the pool.
+	 */
+	virt = kcalloc(count + max_alloc - 1, size, GFP_KERNEL);
+	if (!virt)
+		return -ENOMEM;
+
+	pool->base = virt;
+	/* If the allocator gave us any extra memory, use it */
+	pool->count = ksize(pool->base) / size;
+	pool->free = 0;
+	pool->max_alloc = max_alloc;
+	pool->size = size;
+	pool->addr = 0;		/* Only used for DMA pools */
+
+	return 0;
+}
+
+void gsi_trans_pool_exit(struct gsi_trans_pool *pool)
+{
+	kfree(pool->base);
+	memset(pool, 0, sizeof(*pool));
+}
+
+/* Home-grown DMA pool.  This way we can preallocate the pool, and guarantee
+ * allocations will succeed.  The immediate commands in a transaction can
+ * require up to max_alloc elements from the pool.  But we only allow
+ * allocation of a single element from a DMA pool at a time.
+ */
+int gsi_trans_pool_init_dma(struct device *dev, struct gsi_trans_pool *pool,
+			    size_t size, u32 count, u32 max_alloc)
+{
+	size_t total_size;
+	dma_addr_t addr;
+	void *virt;
+
+	if (!size)
+		return -EINVAL;
+	if (count < max_alloc)
+		return -EINVAL;
+	if (!max_alloc)
+		return -EINVAL;
+
+	/* Don't let allocations cross a power-of-two boundary */
+	size = __roundup_pow_of_two(size);
+	total_size = (count + max_alloc - 1) * size;
+
+	/* The allocator will give us a power-of-2 number of pages
+	 * sufficient to satisfy our request.  Round up our requested
+	 * size to avoid any unused space in the allocation.  This way
+	 * gsi_trans_pool_exit_dma() can assume the total allocated
+	 * size is exactly (count * size).
+	 */
+	total_size = PAGE_SIZE << get_order(total_size);
+
+	virt = dma_alloc_coherent(dev, total_size, &addr, GFP_KERNEL);
+	if (!virt)
+		return -ENOMEM;
+
+	pool->base = virt;
+	pool->count = total_size / size;
+	pool->free = 0;
+	pool->size = size;
+	pool->max_alloc = max_alloc;
+	pool->addr = addr;
+
+	return 0;
+}
+
+void gsi_trans_pool_exit_dma(struct device *dev, struct gsi_trans_pool *pool)
+{
+	size_t total_size = pool->count * pool->size;
+
+	dma_free_coherent(dev, total_size, pool->base, pool->addr);
+	memset(pool, 0, sizeof(*pool));
+}
+
+/* Return the byte offset of the next free entry in the pool */
+static u32 gsi_trans_pool_alloc_common(struct gsi_trans_pool *pool, u32 count)
+{
+	u32 offset;
+
+	WARN_ON(!count);
+	WARN_ON(count > pool->max_alloc);
+
+	/* Allocate from beginning if wrap would occur */
+	if (count > pool->count - pool->free)
+		pool->free = 0;
+
+	offset = pool->free * pool->size;
+	pool->free += count;
+	memset(pool->base + offset, 0, count * pool->size);
+
+	return offset;
+}
+
+/* Allocate a contiguous block of zeroed entries from a pool */
+void *gsi_trans_pool_alloc(struct gsi_trans_pool *pool, u32 count)
+{
+	return pool->base + gsi_trans_pool_alloc_common(pool, count);
+}
+
+/* Allocate a single zeroed entry from a DMA pool */
+void *gsi_trans_pool_alloc_dma(struct gsi_trans_pool *pool, dma_addr_t *addr)
+{
+	u32 offset = gsi_trans_pool_alloc_common(pool, 1);
+
+	*addr = pool->addr + offset;
+
+	return pool->base + offset;
+}
+
+/* Map a TRE ring entry index to the transaction it is associated with */
+static void gsi_trans_map(struct gsi_trans *trans, u32 index)
+{
+	struct gsi_channel *channel = &trans->gsi->channel[trans->channel_id];
+
+	/* The completion event will indicate the last TRE used */
+	index += trans->used_count - 1;
+
+	/* Note: index *must* be used modulo the ring count here */
+	channel->trans_info.map[index % channel->tre_ring.count] = trans;
+}
+
+/* Return the transaction mapped to a given ring entry */
+struct gsi_trans *
+gsi_channel_trans_mapped(struct gsi_channel *channel, u32 index)
+{
+	/* Note: index *must* be used modulo the ring count here */
+	return channel->trans_info.map[index % channel->tre_ring.count];
+}
+
+/* Return the oldest completed transaction for a channel (or null) */
+struct gsi_trans *gsi_channel_trans_complete(struct gsi_channel *channel)
+{
+	struct gsi_trans_info *trans_info = &channel->trans_info;
+	u16 trans_id = trans_info->completed_id;
+
+	if (trans_id == trans_info->pending_id) {
+		gsi_channel_update(channel);
+		if (trans_id == trans_info->pending_id)
+			return NULL;
+	}
+
+	return &trans_info->trans[trans_id %= channel->tre_count];
+}
+
+/* Move a transaction from allocated to committed state */
+static void gsi_trans_move_committed(struct gsi_trans *trans)
+{
+	struct gsi_channel *channel = &trans->gsi->channel[trans->channel_id];
+	struct gsi_trans_info *trans_info = &channel->trans_info;
+
+	/* This allocated transaction is now committed */
+	trans_info->allocated_id++;
+}
+
+/* Move committed transactions to pending state */
+static void gsi_trans_move_pending(struct gsi_trans *trans)
+{
+	struct gsi_channel *channel = &trans->gsi->channel[trans->channel_id];
+	struct gsi_trans_info *trans_info = &channel->trans_info;
+	u16 trans_index = trans - &trans_info->trans[0];
+	u16 delta;
+
+	/* These committed transactions are now pending */
+	delta = trans_index - trans_info->committed_id + 1;
+	trans_info->committed_id += delta % channel->tre_count;
+}
+
+/* Move pending transactions to completed state */
+void gsi_trans_move_complete(struct gsi_trans *trans)
+{
+	struct gsi_channel *channel = &trans->gsi->channel[trans->channel_id];
+	struct gsi_trans_info *trans_info = &channel->trans_info;
+	u16 trans_index = trans - trans_info->trans;
+	u16 delta;
+
+	/* These pending transactions are now completed */
+	delta = trans_index - trans_info->pending_id + 1;
+	delta %= channel->tre_count;
+	trans_info->pending_id += delta;
+}
+
+/* Move a transaction from completed to polled state */
+void gsi_trans_move_polled(struct gsi_trans *trans)
+{
+	struct gsi_channel *channel = &trans->gsi->channel[trans->channel_id];
+	struct gsi_trans_info *trans_info = &channel->trans_info;
+
+	/* This completed transaction is now polled */
+	trans_info->completed_id++;
+}
+
+/* Reserve some number of TREs on a channel.  Returns true if successful */
+static bool
+gsi_trans_tre_reserve(struct gsi_trans_info *trans_info, u32 tre_count)
+{
+	int avail = atomic_read(&trans_info->tre_avail);
+	int new;
+
+	do {
+		new = avail - (int)tre_count;
+		if (unlikely(new < 0))
+			return false;
+	} while (!atomic_try_cmpxchg(&trans_info->tre_avail, &avail, new));
+
+	return true;
+}
+
+/* Release previously-reserved TRE entries to a channel */
+static void
+gsi_trans_tre_release(struct gsi_trans_info *trans_info, u32 tre_count)
+{
+	atomic_add(tre_count, &trans_info->tre_avail);
+}
+
+/* Return true if no transactions are allocated, false otherwise */
+bool gsi_channel_trans_idle(struct gsi *gsi, u32 channel_id)
+{
+	u32 tre_max = gsi_channel_tre_max(gsi, channel_id);
+	struct gsi_trans_info *trans_info;
+
+	trans_info = &gsi->channel[channel_id].trans_info;
+
+	return atomic_read(&trans_info->tre_avail) == tre_max;
+}
+
+/* Allocate a GSI transaction on a channel */
+struct gsi_trans *gsi_channel_trans_alloc(struct gsi *gsi, u32 channel_id,
+					  u32 tre_count,
+					  enum dma_data_direction direction)
+{
+	struct gsi_channel *channel = &gsi->channel[channel_id];
+	struct gsi_trans_info *trans_info;
+	struct gsi_trans *trans;
+	u16 trans_index;
+
+	if (WARN_ON(tre_count > channel->trans_tre_max))
+		return NULL;
+
+	trans_info = &channel->trans_info;
+
+	/* If we can't reserve the TREs for the transaction, we're done */
+	if (!gsi_trans_tre_reserve(trans_info, tre_count))
+		return NULL;
+
+	trans_index = trans_info->free_id % channel->tre_count;
+	trans = &trans_info->trans[trans_index];
+	memset(trans, 0, sizeof(*trans));
+
+	/* Initialize non-zero fields in the transaction */
+	trans->gsi = gsi;
+	trans->channel_id = channel_id;
+	trans->rsvd_count = tre_count;
+	init_completion(&trans->completion);
+
+	/* Allocate the scatterlist */
+	trans->sgl = gsi_trans_pool_alloc(&trans_info->sg_pool, tre_count);
+	sg_init_marker(trans->sgl, tre_count);
+
+	trans->direction = direction;
+	refcount_set(&trans->refcount, 1);
+
+	/* This free transaction is now allocated */
+	trans_info->free_id++;
+
+	return trans;
+}
+
+/* Free a previously-allocated transaction */
+void gsi_trans_free(struct gsi_trans *trans)
+{
+	struct gsi_trans_info *trans_info;
+
+	if (!refcount_dec_and_test(&trans->refcount))
+		return;
+
+	/* Unused transactions are allocated but never committed, pending,
+	 * completed, or polled.
+	 */
+	trans_info = &trans->gsi->channel[trans->channel_id].trans_info;
+	if (!trans->used_count) {
+		trans_info->allocated_id++;
+		trans_info->committed_id++;
+		trans_info->pending_id++;
+		trans_info->completed_id++;
+	} else {
+		ipa_gsi_trans_release(trans);
+	}
+
+	/* This transaction is now free */
+	trans_info->polled_id++;
+
+	/* Releasing the reserved TREs implicitly frees the sgl[] and
+	 * (if present) info[] arrays, plus the transaction itself.
+	 */
+	gsi_trans_tre_release(trans_info, trans->rsvd_count);
+}
+
+/* Add an immediate command to a transaction */
+void gsi_trans_cmd_add(struct gsi_trans *trans, void *buf, u32 size,
+		       dma_addr_t addr, enum ipa_cmd_opcode opcode)
+{
+	u32 which = trans->used_count++;
+	struct scatterlist *sg;
+
+	WARN_ON(which >= trans->rsvd_count);
+
+	/* Commands are quite different from data transfer requests.
+	 * Their payloads come from a pool whose memory is allocated
+	 * using dma_alloc_coherent().  We therefore do *not* map them
+	 * for DMA (unlike what we do for pages and skbs).
+	 *
+	 * When a transaction completes, the SGL is normally unmapped.
+	 * A command transaction has direction DMA_NONE, which tells
+	 * gsi_trans_complete() to skip the unmapping step.
+	 *
+	 * The only things we use directly in a command scatter/gather
+	 * entry are the DMA address and length.  We still need the SG
+	 * table flags to be maintained though, so assign a NULL page
+	 * pointer for that purpose.
+	 */
+	sg = &trans->sgl[which];
+	sg_assign_page(sg, NULL);
+	sg_dma_address(sg) = addr;
+	sg_dma_len(sg) = size;
+
+	trans->cmd_opcode[which] = opcode;
+}
+
+/* Add a page transfer to a transaction.  It will fill the only TRE. */
+int gsi_trans_page_add(struct gsi_trans *trans, struct page *page, u32 size,
+		       u32 offset)
+{
+	struct scatterlist *sg = &trans->sgl[0];
+	int ret;
+
+	if (WARN_ON(trans->rsvd_count != 1))
+		return -EINVAL;
+	if (WARN_ON(trans->used_count))
+		return -EINVAL;
+
+	sg_set_page(sg, page, size, offset);
+	ret = dma_map_sg(trans->gsi->dev, sg, 1, trans->direction);
+	if (!ret)
+		return -ENOMEM;
+
+	trans->used_count++;	/* Transaction now owns the (DMA mapped) page */
+
+	return 0;
+}
+
+/* Add an SKB transfer to a transaction.  No other TREs will be used. */
+int gsi_trans_skb_add(struct gsi_trans *trans, struct sk_buff *skb)
+{
+	struct scatterlist *sg = &trans->sgl[0];
+	u32 used_count;
+	int ret;
+
+	if (WARN_ON(trans->rsvd_count != 1))
+		return -EINVAL;
+	if (WARN_ON(trans->used_count))
+		return -EINVAL;
+
+	/* skb->len will not be 0 (checked early) */
+	ret = skb_to_sgvec(skb, sg, 0, skb->len);
+	if (ret < 0)
+		return ret;
+	used_count = ret;
+
+	ret = dma_map_sg(trans->gsi->dev, sg, used_count, trans->direction);
+	if (!ret)
+		return -ENOMEM;
+
+	/* Transaction now owns the (DMA mapped) skb */
+	trans->used_count += used_count;
+
+	return 0;
+}
+
+/* Compute the length/opcode value to use for a TRE */
+static __le16 gsi_tre_len_opcode(enum ipa_cmd_opcode opcode, u32 len)
+{
+	return opcode == IPA_CMD_NONE ? cpu_to_le16((u16)len)
+				      : cpu_to_le16((u16)opcode);
+}
+
+/* Compute the flags value to use for a given TRE */
+static __le32 gsi_tre_flags(bool last_tre, bool bei, enum ipa_cmd_opcode opcode)
+{
+	enum gsi_tre_type tre_type;
+	u32 tre_flags;
+
+	tre_type = opcode == IPA_CMD_NONE ? GSI_RE_XFER : GSI_RE_IMMD_CMD;
+	tre_flags = u32_encode_bits(tre_type, TRE_FLAGS_TYPE_FMASK);
+
+	/* Last TRE contains interrupt flags */
+	if (last_tre) {
+		/* All transactions end in a transfer completion interrupt */
+		tre_flags |= TRE_FLAGS_IEOT_FMASK;
+		/* Don't interrupt when outbound commands are acknowledged */
+		if (bei)
+			tre_flags |= TRE_FLAGS_BEI_FMASK;
+	} else {	/* All others indicate there's more to come */
+		tre_flags |= TRE_FLAGS_CHAIN_FMASK;
+	}
+
+	return cpu_to_le32(tre_flags);
+}
+
+static void gsi_trans_tre_fill(struct gsi_tre *dest_tre, dma_addr_t addr,
+			       u32 len, bool last_tre, bool bei,
+			       enum ipa_cmd_opcode opcode)
+{
+	struct gsi_tre tre;
+
+	tre.addr = cpu_to_le64(addr);
+	tre.len_opcode = gsi_tre_len_opcode(opcode, len);
+	tre.reserved = 0;
+	tre.flags = gsi_tre_flags(last_tre, bei, opcode);
+
+	/* ARM64 can write 16 bytes as a unit with a single instruction.
+	 * Doing the assignment this way is an attempt to make that happen.
+	 */
+	*dest_tre = tre;
+}
+
+/**
+ * __gsi_trans_commit() - Common GSI transaction commit code
+ * @trans:	Transaction to commit
+ * @ring_db:	Whether to tell the hardware about these queued transfers
+ *
+ * Formats channel ring TRE entries based on the content of the scatterlist.
+ * Maps a transaction pointer to the last ring entry used for the transaction,
+ * so it can be recovered when it completes.  Moves the transaction to
+ * pending state.  Finally, updates the channel ring pointer and optionally
+ * rings the doorbell.
+ */
+static void __gsi_trans_commit(struct gsi_trans *trans, bool ring_db)
+{
+	struct gsi_channel *channel = &trans->gsi->channel[trans->channel_id];
+	struct gsi_ring *tre_ring = &channel->tre_ring;
+	enum ipa_cmd_opcode opcode = IPA_CMD_NONE;
+	bool bei = channel->toward_ipa;
+	struct gsi_tre *dest_tre;
+	struct scatterlist *sg;
+	u32 byte_count = 0;
+	u8 *cmd_opcode;
+	u32 avail;
+	u32 i;
+
+	WARN_ON(!trans->used_count);
+
+	/* Consume the entries.  If we cross the end of the ring while
+	 * filling them we'll switch to the beginning to finish.
+	 * If there is no info array we're doing a simple data
+	 * transfer request, whose opcode is IPA_CMD_NONE.
+	 */
+	cmd_opcode = channel->command ? &trans->cmd_opcode[0] : NULL;
+	avail = tre_ring->count - tre_ring->index % tre_ring->count;
+	dest_tre = gsi_ring_virt(tre_ring, tre_ring->index);
+	for_each_sg(trans->sgl, sg, trans->used_count, i) {
+		bool last_tre = i == trans->used_count - 1;
+		dma_addr_t addr = sg_dma_address(sg);
+		u32 len = sg_dma_len(sg);
+
+		byte_count += len;
+		if (!avail--)
+			dest_tre = gsi_ring_virt(tre_ring, 0);
+		if (cmd_opcode)
+			opcode = *cmd_opcode++;
+
+		gsi_trans_tre_fill(dest_tre, addr, len, last_tre, bei, opcode);
+		dest_tre++;
+	}
+	/* Associate the TRE with the transaction */
+	gsi_trans_map(trans, tre_ring->index);
+
+	tre_ring->index += trans->used_count;
+
+	trans->len = byte_count;
+	if (channel->toward_ipa)
+		gsi_trans_tx_committed(trans);
+
+	gsi_trans_move_committed(trans);
+
+	/* Ring doorbell if requested, or if all TREs are allocated */
+	if (ring_db || !atomic_read(&channel->trans_info.tre_avail)) {
+		/* Report what we're handing off to hardware for TX channels */
+		if (channel->toward_ipa)
+			gsi_trans_tx_queued(trans);
+		gsi_trans_move_pending(trans);
+		gsi_channel_doorbell(channel);
+	}
+}
+
+/* Commit a GSI transaction */
+void gsi_trans_commit(struct gsi_trans *trans, bool ring_db)
+{
+	if (trans->used_count)
+		__gsi_trans_commit(trans, ring_db);
+	else
+		gsi_trans_free(trans);
+}
+
+/* Commit a GSI transaction and wait for it to complete */
+void gsi_trans_commit_wait(struct gsi_trans *trans)
+{
+	if (!trans->used_count)
+		goto out_trans_free;
+
+	refcount_inc(&trans->refcount);
+
+	__gsi_trans_commit(trans, true);
+
+	wait_for_completion(&trans->completion);
+
+out_trans_free:
+	gsi_trans_free(trans);
+}
+
+/* Process the completion of a transaction; called while polling */
+void gsi_trans_complete(struct gsi_trans *trans)
+{
+	/* If the entire SGL was mapped when added, unmap it now */
+	if (trans->direction != DMA_NONE)
+		dma_unmap_sg(trans->gsi->dev, trans->sgl, trans->used_count,
+			     trans->direction);
+
+	ipa_gsi_trans_complete(trans);
+
+	complete(&trans->completion);
+
+	gsi_trans_free(trans);
+}
+
+/* Cancel a channel's pending transactions */
+void gsi_channel_trans_cancel_pending(struct gsi_channel *channel)
+{
+	struct gsi_trans_info *trans_info = &channel->trans_info;
+	u16 trans_id = trans_info->pending_id;
+
+	/* channel->gsi->mutex is held by caller */
+
+	/* If there are no pending transactions, we're done */
+	if (trans_id == trans_info->committed_id)
+		return;
+
+	/* Mark all pending transactions cancelled */
+	do {
+		struct gsi_trans *trans;
+
+		trans = &trans_info->trans[trans_id % channel->tre_count];
+		trans->cancelled = true;
+	} while (++trans_id != trans_info->committed_id);
+
+	/* All pending transactions are now completed */
+	trans_info->pending_id = trans_info->committed_id;
+
+	/* Schedule NAPI polling to complete the cancelled transactions */
+	napi_schedule(&channel->napi);
+}
+
+/* Issue a command to read a single byte from a channel */
+int gsi_trans_read_byte(struct gsi *gsi, u32 channel_id, dma_addr_t addr)
+{
+	struct gsi_channel *channel = &gsi->channel[channel_id];
+	struct gsi_ring *tre_ring = &channel->tre_ring;
+	struct gsi_trans_info *trans_info;
+	struct gsi_tre *dest_tre;
+
+	trans_info = &channel->trans_info;
+
+	/* First reserve the TRE, if possible */
+	if (!gsi_trans_tre_reserve(trans_info, 1))
+		return -EBUSY;
+
+	/* Now fill the reserved TRE and tell the hardware */
+
+	dest_tre = gsi_ring_virt(tre_ring, tre_ring->index);
+	gsi_trans_tre_fill(dest_tre, addr, 1, true, false, IPA_CMD_NONE);
+
+	tre_ring->index++;
+	gsi_channel_doorbell(channel);
+
+	return 0;
+}
+
+/* Mark a gsi_trans_read_byte() request done */
+void gsi_trans_read_byte_done(struct gsi *gsi, u32 channel_id)
+{
+	struct gsi_channel *channel = &gsi->channel[channel_id];
+
+	gsi_trans_tre_release(&channel->trans_info, 1);
+}
+
+/* Initialize a channel's GSI transaction info */
+int gsi_channel_trans_init(struct gsi *gsi, u32 channel_id)
+{
+	struct gsi_channel *channel = &gsi->channel[channel_id];
+	u32 tre_count = channel->tre_count;
+	struct gsi_trans_info *trans_info;
+	u32 tre_max;
+	int ret;
+
+	/* Ensure the size of a channel element is what's expected */
+	BUILD_BUG_ON(sizeof(struct gsi_tre) != GSI_RING_ELEMENT_SIZE);
+
+	trans_info = &channel->trans_info;
+
+	/* The tre_avail field is what ultimately limits the number of
+	 * outstanding transactions and their resources.  A transaction
+	 * allocation succeeds only if the TREs available are sufficient
+	 * for what the transaction might need.
+	 */
+	tre_max = gsi_channel_tre_max(channel->gsi, channel_id);
+	atomic_set(&trans_info->tre_avail, tre_max);
+
+	/* We can't use more TREs than the number available in the ring.
+	 * This limits the number of transactions that can be outstanding.
+	 * Worst case is one TRE per transaction (but we actually limit
+	 * it to something a little less than that).  By allocating a
+	 * power-of-two number of transactions we can use an index
+	 * modulo that number to determine the next one that's free.
+	 * Transactions are allocated one at a time.
+	 */
+	trans_info->trans = kcalloc(tre_count, sizeof(*trans_info->trans),
+				    GFP_KERNEL);
+	if (!trans_info->trans)
+		return -ENOMEM;
+	trans_info->free_id = 0;	/* all modulo channel->tre_count */
+	trans_info->allocated_id = 0;
+	trans_info->committed_id = 0;
+	trans_info->pending_id = 0;
+	trans_info->completed_id = 0;
+	trans_info->polled_id = 0;
+
+	/* A completion event contains a pointer to the TRE that caused
+	 * the event (which will be the last one used by the transaction).
+	 * Each entry in this map records the transaction associated
+	 * with a corresponding completed TRE.
+	 */
+	trans_info->map = kcalloc(tre_count, sizeof(*trans_info->map),
+				  GFP_KERNEL);
+	if (!trans_info->map) {
+		ret = -ENOMEM;
+		goto err_trans_free;
+	}
+
+	/* A transaction uses a scatterlist array to represent the data
+	 * transfers implemented by the transaction.  Each scatterlist
+	 * element is used to fill a single TRE when the transaction is
+	 * committed.  So we need as many scatterlist elements as the
+	 * maximum number of TREs that can be outstanding.
+	 */
+	ret = gsi_trans_pool_init(&trans_info->sg_pool,
+				  sizeof(struct scatterlist),
+				  tre_max, channel->trans_tre_max);
+	if (ret)
+		goto err_map_free;
+
+
+	return 0;
+
+err_map_free:
+	kfree(trans_info->map);
+err_trans_free:
+	kfree(trans_info->trans);
+
+	dev_err(gsi->dev, "error %d initializing channel %u transactions\n",
+		ret, channel_id);
+
+	return ret;
+}
+
+/* Inverse of gsi_channel_trans_init() */
+void gsi_channel_trans_exit(struct gsi_channel *channel)
+{
+	struct gsi_trans_info *trans_info = &channel->trans_info;
+
+	gsi_trans_pool_exit(&trans_info->sg_pool);
+	kfree(trans_info->trans);
+	kfree(trans_info->map);
+}