diff options
Diffstat (limited to 'drivers/hwtracing/stm/core.c')
| -rw-r--r-- | drivers/hwtracing/stm/core.c | 1363 |
1 files changed, 1363 insertions, 0 deletions
diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c new file mode 100644 index 000000000..2712e699b --- /dev/null +++ b/drivers/hwtracing/stm/core.c @@ -0,0 +1,1363 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * System Trace Module (STM) infrastructure + * Copyright (c) 2014, Intel Corporation. + * + * STM class implements generic infrastructure for System Trace Module devices + * as defined in MIPI STPv2 specification. + */ + +#include <linux/pm_runtime.h> +#include <linux/uaccess.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/device.h> +#include <linux/compat.h> +#include <linux/kdev_t.h> +#include <linux/srcu.h> +#include <linux/slab.h> +#include <linux/stm.h> +#include <linux/fs.h> +#include <linux/mm.h> +#include <linux/vmalloc.h> +#include "stm.h" + +#include <uapi/linux/stm.h> + +static unsigned int stm_core_up; + +/* + * The SRCU here makes sure that STM device doesn't disappear from under a + * stm_source_write() caller, which may want to have as little overhead as + * possible. + */ +static struct srcu_struct stm_source_srcu; + +static ssize_t masters_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct stm_device *stm = to_stm_device(dev); + int ret; + + ret = sprintf(buf, "%u %u\n", stm->data->sw_start, stm->data->sw_end); + + return ret; +} + +static DEVICE_ATTR_RO(masters); + +static ssize_t channels_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct stm_device *stm = to_stm_device(dev); + int ret; + + ret = sprintf(buf, "%u\n", stm->data->sw_nchannels); + + return ret; +} + +static DEVICE_ATTR_RO(channels); + +static ssize_t hw_override_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct stm_device *stm = to_stm_device(dev); + int ret; + + ret = sprintf(buf, "%u\n", stm->data->hw_override); + + return ret; +} + +static DEVICE_ATTR_RO(hw_override); + +static struct attribute *stm_attrs[] = { + &dev_attr_masters.attr, + &dev_attr_channels.attr, + &dev_attr_hw_override.attr, + NULL, +}; + +ATTRIBUTE_GROUPS(stm); + +static struct class stm_class = { + .name = "stm", + .dev_groups = stm_groups, +}; + +/** + * stm_find_device() - find stm device by name + * @buf: character buffer containing the name + * + * This is called when either policy gets assigned to an stm device or an + * stm_source device gets linked to an stm device. + * + * This grabs device's reference (get_device()) and module reference, both + * of which the calling path needs to make sure to drop with stm_put_device(). + * + * Return: stm device pointer or null if lookup failed. + */ +struct stm_device *stm_find_device(const char *buf) +{ + struct stm_device *stm; + struct device *dev; + + if (!stm_core_up) + return NULL; + + dev = class_find_device_by_name(&stm_class, buf); + if (!dev) + return NULL; + + stm = to_stm_device(dev); + if (!try_module_get(stm->owner)) { + /* matches class_find_device() above */ + put_device(dev); + return NULL; + } + + return stm; +} + +/** + * stm_put_device() - drop references on the stm device + * @stm: stm device, previously acquired by stm_find_device() + * + * This drops the module reference and device reference taken by + * stm_find_device() or stm_char_open(). + */ +void stm_put_device(struct stm_device *stm) +{ + module_put(stm->owner); + put_device(&stm->dev); +} + +/* + * Internally we only care about software-writable masters here, that is the + * ones in the range [stm_data->sw_start..stm_data..sw_end], however we need + * original master numbers to be visible externally, since they are the ones + * that will appear in the STP stream. Thus, the internal bookkeeping uses + * $master - stm_data->sw_start to reference master descriptors and such. + */ + +#define __stm_master(_s, _m) \ + ((_s)->masters[(_m) - (_s)->data->sw_start]) + +static inline struct stp_master * +stm_master(struct stm_device *stm, unsigned int idx) +{ + if (idx < stm->data->sw_start || idx > stm->data->sw_end) + return NULL; + + return __stm_master(stm, idx); +} + +static int stp_master_alloc(struct stm_device *stm, unsigned int idx) +{ + struct stp_master *master; + + master = kzalloc(struct_size(master, chan_map, + BITS_TO_LONGS(stm->data->sw_nchannels)), + GFP_ATOMIC); + if (!master) + return -ENOMEM; + + master->nr_free = stm->data->sw_nchannels; + __stm_master(stm, idx) = master; + + return 0; +} + +static void stp_master_free(struct stm_device *stm, unsigned int idx) +{ + struct stp_master *master = stm_master(stm, idx); + + if (!master) + return; + + __stm_master(stm, idx) = NULL; + kfree(master); +} + +static void stm_output_claim(struct stm_device *stm, struct stm_output *output) +{ + struct stp_master *master = stm_master(stm, output->master); + + lockdep_assert_held(&stm->mc_lock); + lockdep_assert_held(&output->lock); + + if (WARN_ON_ONCE(master->nr_free < output->nr_chans)) + return; + + bitmap_allocate_region(&master->chan_map[0], output->channel, + ilog2(output->nr_chans)); + + master->nr_free -= output->nr_chans; +} + +static void +stm_output_disclaim(struct stm_device *stm, struct stm_output *output) +{ + struct stp_master *master = stm_master(stm, output->master); + + lockdep_assert_held(&stm->mc_lock); + lockdep_assert_held(&output->lock); + + bitmap_release_region(&master->chan_map[0], output->channel, + ilog2(output->nr_chans)); + + master->nr_free += output->nr_chans; + output->nr_chans = 0; +} + +/* + * This is like bitmap_find_free_region(), except it can ignore @start bits + * at the beginning. + */ +static int find_free_channels(unsigned long *bitmap, unsigned int start, + unsigned int end, unsigned int width) +{ + unsigned int pos; + int i; + + for (pos = start; pos < end + 1; pos = ALIGN(pos, width)) { + pos = find_next_zero_bit(bitmap, end + 1, pos); + if (pos + width > end + 1) + break; + + if (pos & (width - 1)) + continue; + + for (i = 1; i < width && !test_bit(pos + i, bitmap); i++) + ; + if (i == width) + return pos; + + /* step over [pos..pos+i) to continue search */ + pos += i; + } + + return -1; +} + +static int +stm_find_master_chan(struct stm_device *stm, unsigned int width, + unsigned int *mstart, unsigned int mend, + unsigned int *cstart, unsigned int cend) +{ + struct stp_master *master; + unsigned int midx; + int pos, err; + + for (midx = *mstart; midx <= mend; midx++) { + if (!stm_master(stm, midx)) { + err = stp_master_alloc(stm, midx); + if (err) + return err; + } + + master = stm_master(stm, midx); + + if (!master->nr_free) + continue; + + pos = find_free_channels(master->chan_map, *cstart, cend, + width); + if (pos < 0) + continue; + + *mstart = midx; + *cstart = pos; + return 0; + } + + return -ENOSPC; +} + +static int stm_output_assign(struct stm_device *stm, unsigned int width, + struct stp_policy_node *policy_node, + struct stm_output *output) +{ + unsigned int midx, cidx, mend, cend; + int ret = -EINVAL; + + if (width > stm->data->sw_nchannels) + return -EINVAL; + + /* We no longer accept policy_node==NULL here */ + if (WARN_ON_ONCE(!policy_node)) + return -EINVAL; + + /* + * Also, the caller holds reference to policy_node, so it won't + * disappear on us. + */ + stp_policy_node_get_ranges(policy_node, &midx, &mend, &cidx, &cend); + + spin_lock(&stm->mc_lock); + spin_lock(&output->lock); + /* output is already assigned -- shouldn't happen */ + if (WARN_ON_ONCE(output->nr_chans)) + goto unlock; + + ret = stm_find_master_chan(stm, width, &midx, mend, &cidx, cend); + if (ret < 0) + goto unlock; + + output->master = midx; + output->channel = cidx; + output->nr_chans = width; + if (stm->pdrv->output_open) { + void *priv = stp_policy_node_priv(policy_node); + + if (WARN_ON_ONCE(!priv)) + goto unlock; + + /* configfs subsys mutex is held by the caller */ + ret = stm->pdrv->output_open(priv, output); + if (ret) + goto unlock; + } + + stm_output_claim(stm, output); + dev_dbg(&stm->dev, "assigned %u:%u (+%u)\n", midx, cidx, width); + + ret = 0; +unlock: + if (ret) + output->nr_chans = 0; + + spin_unlock(&output->lock); + spin_unlock(&stm->mc_lock); + + return ret; +} + +static void stm_output_free(struct stm_device *stm, struct stm_output *output) +{ + spin_lock(&stm->mc_lock); + spin_lock(&output->lock); + if (output->nr_chans) + stm_output_disclaim(stm, output); + if (stm->pdrv && stm->pdrv->output_close) + stm->pdrv->output_close(output); + spin_unlock(&output->lock); + spin_unlock(&stm->mc_lock); +} + +static void stm_output_init(struct stm_output *output) +{ + spin_lock_init(&output->lock); +} + +static int major_match(struct device *dev, const void *data) +{ + unsigned int major = *(unsigned int *)data; + + return MAJOR(dev->devt) == major; +} + +/* + * Framing protocol management + * Modules can implement STM protocol drivers and (un-)register them + * with the STM class framework. + */ +static struct list_head stm_pdrv_head; +static struct mutex stm_pdrv_mutex; + +struct stm_pdrv_entry { + struct list_head entry; + const struct stm_protocol_driver *pdrv; + const struct config_item_type *node_type; +}; + +static const struct stm_pdrv_entry * +__stm_lookup_protocol(const char *name) +{ + struct stm_pdrv_entry *pe; + + /* + * If no name is given (NULL or ""), fall back to "p_basic". + */ + if (!name || !*name) + name = "p_basic"; + + list_for_each_entry(pe, &stm_pdrv_head, entry) { + if (!strcmp(name, pe->pdrv->name)) + return pe; + } + + return NULL; +} + +int stm_register_protocol(const struct stm_protocol_driver *pdrv) +{ + struct stm_pdrv_entry *pe = NULL; + int ret = -ENOMEM; + + mutex_lock(&stm_pdrv_mutex); + + if (__stm_lookup_protocol(pdrv->name)) { + ret = -EEXIST; + goto unlock; + } + + pe = kzalloc(sizeof(*pe), GFP_KERNEL); + if (!pe) + goto unlock; + + if (pdrv->policy_attr) { + pe->node_type = get_policy_node_type(pdrv->policy_attr); + if (!pe->node_type) + goto unlock; + } + + list_add_tail(&pe->entry, &stm_pdrv_head); + pe->pdrv = pdrv; + + ret = 0; +unlock: + mutex_unlock(&stm_pdrv_mutex); + + if (ret) + kfree(pe); + + return ret; +} +EXPORT_SYMBOL_GPL(stm_register_protocol); + +void stm_unregister_protocol(const struct stm_protocol_driver *pdrv) +{ + struct stm_pdrv_entry *pe, *iter; + + mutex_lock(&stm_pdrv_mutex); + + list_for_each_entry_safe(pe, iter, &stm_pdrv_head, entry) { + if (pe->pdrv == pdrv) { + list_del(&pe->entry); + + if (pe->node_type) { + kfree(pe->node_type->ct_attrs); + kfree(pe->node_type); + } + kfree(pe); + break; + } + } + + mutex_unlock(&stm_pdrv_mutex); +} +EXPORT_SYMBOL_GPL(stm_unregister_protocol); + +static bool stm_get_protocol(const struct stm_protocol_driver *pdrv) +{ + return try_module_get(pdrv->owner); +} + +void stm_put_protocol(const struct stm_protocol_driver *pdrv) +{ + module_put(pdrv->owner); +} + +int stm_lookup_protocol(const char *name, + const struct stm_protocol_driver **pdrv, + const struct config_item_type **node_type) +{ + const struct stm_pdrv_entry *pe; + + mutex_lock(&stm_pdrv_mutex); + + pe = __stm_lookup_protocol(name); + if (pe && pe->pdrv && stm_get_protocol(pe->pdrv)) { + *pdrv = pe->pdrv; + *node_type = pe->node_type; + } + + mutex_unlock(&stm_pdrv_mutex); + + return pe ? 0 : -ENOENT; +} + +static int stm_char_open(struct inode *inode, struct file *file) +{ + struct stm_file *stmf; + struct device *dev; + unsigned int major = imajor(inode); + int err = -ENOMEM; + + dev = class_find_device(&stm_class, NULL, &major, major_match); + if (!dev) + return -ENODEV; + + stmf = kzalloc(sizeof(*stmf), GFP_KERNEL); + if (!stmf) + goto err_put_device; + + err = -ENODEV; + stm_output_init(&stmf->output); + stmf->stm = to_stm_device(dev); + + if (!try_module_get(stmf->stm->owner)) + goto err_free; + + file->private_data = stmf; + + return nonseekable_open(inode, file); + +err_free: + kfree(stmf); +err_put_device: + /* matches class_find_device() above */ + put_device(dev); + + return err; +} + +static int stm_char_release(struct inode *inode, struct file *file) +{ + struct stm_file *stmf = file->private_data; + struct stm_device *stm = stmf->stm; + + if (stm->data->unlink) + stm->data->unlink(stm->data, stmf->output.master, + stmf->output.channel); + + stm_output_free(stm, &stmf->output); + + /* + * matches the stm_char_open()'s + * class_find_device() + try_module_get() + */ + stm_put_device(stm); + kfree(stmf); + + return 0; +} + +static int +stm_assign_first_policy(struct stm_device *stm, struct stm_output *output, + char **ids, unsigned int width) +{ + struct stp_policy_node *pn; + int err, n; + + /* + * On success, stp_policy_node_lookup() will return holding the + * configfs subsystem mutex, which is then released in + * stp_policy_node_put(). This allows the pdrv->output_open() in + * stm_output_assign() to serialize against the attribute accessors. + */ + for (n = 0, pn = NULL; ids[n] && !pn; n++) + pn = stp_policy_node_lookup(stm, ids[n]); + + if (!pn) + return -EINVAL; + + err = stm_output_assign(stm, width, pn, output); + + stp_policy_node_put(pn); + + return err; +} + +/** + * stm_data_write() - send the given payload as data packets + * @data: stm driver's data + * @m: STP master + * @c: STP channel + * @ts_first: timestamp the first packet + * @buf: data payload buffer + * @count: data payload size + */ +ssize_t notrace stm_data_write(struct stm_data *data, unsigned int m, + unsigned int c, bool ts_first, const void *buf, + size_t count) +{ + unsigned int flags = ts_first ? STP_PACKET_TIMESTAMPED : 0; + ssize_t sz; + size_t pos; + + for (pos = 0, sz = 0; pos < count; pos += sz) { + sz = min_t(unsigned int, count - pos, 8); + sz = data->packet(data, m, c, STP_PACKET_DATA, flags, sz, + &((u8 *)buf)[pos]); + if (sz <= 0) + break; + + if (ts_first) { + flags = 0; + ts_first = false; + } + } + + return sz < 0 ? sz : pos; +} +EXPORT_SYMBOL_GPL(stm_data_write); + +static ssize_t notrace +stm_write(struct stm_device *stm, struct stm_output *output, + unsigned int chan, const char *buf, size_t count) +{ + int err; + + /* stm->pdrv is serialized against policy_mutex */ + if (!stm->pdrv) + return -ENODEV; + + err = stm->pdrv->write(stm->data, output, chan, buf, count); + if (err < 0) + return err; + + return err; +} + +static ssize_t stm_char_write(struct file *file, const char __user *buf, + size_t count, loff_t *ppos) +{ + struct stm_file *stmf = file->private_data; + struct stm_device *stm = stmf->stm; + char *kbuf; + int err; + + if (count + 1 > PAGE_SIZE) + count = PAGE_SIZE - 1; + + /* + * If no m/c have been assigned to this writer up to this + * point, try to use the task name and "default" policy entries. + */ + if (!stmf->output.nr_chans) { + char comm[sizeof(current->comm)]; + char *ids[] = { comm, "default", NULL }; + + get_task_comm(comm, current); + + err = stm_assign_first_policy(stmf->stm, &stmf->output, ids, 1); + /* + * EBUSY means that somebody else just assigned this + * output, which is just fine for write() + */ + if (err) + return err; + } + + kbuf = kmalloc(count + 1, GFP_KERNEL); + if (!kbuf) + return -ENOMEM; + + err = copy_from_user(kbuf, buf, count); + if (err) { + kfree(kbuf); + return -EFAULT; + } + + pm_runtime_get_sync(&stm->dev); + + count = stm_write(stm, &stmf->output, 0, kbuf, count); + + pm_runtime_mark_last_busy(&stm->dev); + pm_runtime_put_autosuspend(&stm->dev); + kfree(kbuf); + + return count; +} + +static void stm_mmap_open(struct vm_area_struct *vma) +{ + struct stm_file *stmf = vma->vm_file->private_data; + struct stm_device *stm = stmf->stm; + + pm_runtime_get(&stm->dev); +} + +static void stm_mmap_close(struct vm_area_struct *vma) +{ + struct stm_file *stmf = vma->vm_file->private_data; + struct stm_device *stm = stmf->stm; + + pm_runtime_mark_last_busy(&stm->dev); + pm_runtime_put_autosuspend(&stm->dev); +} + +static const struct vm_operations_struct stm_mmap_vmops = { + .open = stm_mmap_open, + .close = stm_mmap_close, +}; + +static int stm_char_mmap(struct file *file, struct vm_area_struct *vma) +{ + struct stm_file *stmf = file->private_data; + struct stm_device *stm = stmf->stm; + unsigned long size, phys; + + if (!stm->data->mmio_addr) + return -EOPNOTSUPP; + + if (vma->vm_pgoff) + return -EINVAL; + + size = vma->vm_end - vma->vm_start; + + if (stmf->output.nr_chans * stm->data->sw_mmiosz != size) + return -EINVAL; + + phys = stm->data->mmio_addr(stm->data, stmf->output.master, + stmf->output.channel, + stmf->output.nr_chans); + + if (!phys) + return -EINVAL; + + pm_runtime_get_sync(&stm->dev); + + vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot); + vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP; + vma->vm_ops = &stm_mmap_vmops; + vm_iomap_memory(vma, phys, size); + + return 0; +} + +static int stm_char_policy_set_ioctl(struct stm_file *stmf, void __user *arg) +{ + struct stm_device *stm = stmf->stm; + struct stp_policy_id *id; + char *ids[] = { NULL, NULL }; + int ret = -EINVAL, wlimit = 1; + u32 size; + + if (stmf->output.nr_chans) + return -EBUSY; + + if (copy_from_user(&size, arg, sizeof(size))) + return -EFAULT; + + if (size < sizeof(*id) || size >= PATH_MAX + sizeof(*id)) + return -EINVAL; + + /* + * size + 1 to make sure the .id string at the bottom is terminated, + * which is also why memdup_user() is not useful here + */ + id = kzalloc(size + 1, GFP_KERNEL); + if (!id) + return -ENOMEM; + + if (copy_from_user(id, arg, size)) { + ret = -EFAULT; + goto err_free; + } + + if (id->__reserved_0 || id->__reserved_1) + goto err_free; + + if (stm->data->sw_mmiosz) + wlimit = PAGE_SIZE / stm->data->sw_mmiosz; + + if (id->width < 1 || id->width > wlimit) + goto err_free; + + ids[0] = id->id; + ret = stm_assign_first_policy(stmf->stm, &stmf->output, ids, + id->width); + if (ret) + goto err_free; + + if (stm->data->link) + ret = stm->data->link(stm->data, stmf->output.master, + stmf->output.channel); + + if (ret) + stm_output_free(stmf->stm, &stmf->output); + +err_free: + kfree(id); + + return ret; +} + +static int stm_char_policy_get_ioctl(struct stm_file *stmf, void __user *arg) +{ + struct stp_policy_id id = { + .size = sizeof(id), + .master = stmf->output.master, + .channel = stmf->output.channel, + .width = stmf->output.nr_chans, + .__reserved_0 = 0, + .__reserved_1 = 0, + }; + + return copy_to_user(arg, &id, id.size) ? -EFAULT : 0; +} + +static long +stm_char_ioctl(struct file *file, unsigned int cmd, unsigned long arg) +{ + struct stm_file *stmf = file->private_data; + struct stm_data *stm_data = stmf->stm->data; + int err = -ENOTTY; + u64 options; + + switch (cmd) { + case STP_POLICY_ID_SET: + err = stm_char_policy_set_ioctl(stmf, (void __user *)arg); + if (err) + return err; + + return stm_char_policy_get_ioctl(stmf, (void __user *)arg); + + case STP_POLICY_ID_GET: + return stm_char_policy_get_ioctl(stmf, (void __user *)arg); + + case STP_SET_OPTIONS: + if (copy_from_user(&options, (u64 __user *)arg, sizeof(u64))) + return -EFAULT; + + if (stm_data->set_options) + err = stm_data->set_options(stm_data, + stmf->output.master, + stmf->output.channel, + stmf->output.nr_chans, + options); + + break; + default: + break; + } + + return err; +} + +static const struct file_operations stm_fops = { + .open = stm_char_open, + .release = stm_char_release, + .write = stm_char_write, + .mmap = stm_char_mmap, + .unlocked_ioctl = stm_char_ioctl, + .compat_ioctl = compat_ptr_ioctl, + .llseek = no_llseek, +}; + +static void stm_device_release(struct device *dev) +{ + struct stm_device *stm = to_stm_device(dev); + + vfree(stm); +} + +int stm_register_device(struct device *parent, struct stm_data *stm_data, + struct module *owner) +{ + struct stm_device *stm; + unsigned int nmasters; + int err = -ENOMEM; + + if (!stm_core_up) + return -EPROBE_DEFER; + + if (!stm_data->packet || !stm_data->sw_nchannels) + return -EINVAL; + + nmasters = stm_data->sw_end - stm_data->sw_start + 1; + stm = vzalloc(sizeof(*stm) + nmasters * sizeof(void *)); + if (!stm) + return -ENOMEM; + + stm->major = register_chrdev(0, stm_data->name, &stm_fops); + if (stm->major < 0) + goto err_free; + + device_initialize(&stm->dev); + stm->dev.devt = MKDEV(stm->major, 0); + stm->dev.class = &stm_class; + stm->dev.parent = parent; + stm->dev.release = stm_device_release; + + mutex_init(&stm->link_mutex); + spin_lock_init(&stm->link_lock); + INIT_LIST_HEAD(&stm->link_list); + + /* initialize the object before it is accessible via sysfs */ + spin_lock_init(&stm->mc_lock); + mutex_init(&stm->policy_mutex); + stm->sw_nmasters = nmasters; + stm->owner = owner; + stm->data = stm_data; + stm_data->stm = stm; + + err = kobject_set_name(&stm->dev.kobj, "%s", stm_data->name); + if (err) + goto err_device; + + err = device_add(&stm->dev); + if (err) + goto err_device; + + /* + * Use delayed autosuspend to avoid bouncing back and forth + * on recurring character device writes, with the initial + * delay time of 2 seconds. + */ + pm_runtime_no_callbacks(&stm->dev); + pm_runtime_use_autosuspend(&stm->dev); + pm_runtime_set_autosuspend_delay(&stm->dev, 2000); + pm_runtime_set_suspended(&stm->dev); + pm_runtime_enable(&stm->dev); + + return 0; + +err_device: + unregister_chrdev(stm->major, stm_data->name); + + /* matches device_initialize() above */ + put_device(&stm->dev); +err_free: + vfree(stm); + + return err; +} +EXPORT_SYMBOL_GPL(stm_register_device); + +static int __stm_source_link_drop(struct stm_source_device *src, + struct stm_device *stm); + +void stm_unregister_device(struct stm_data *stm_data) +{ + struct stm_device *stm = stm_data->stm; + struct stm_source_device *src, *iter; + int i, ret; + + pm_runtime_dont_use_autosuspend(&stm->dev); + pm_runtime_disable(&stm->dev); + + mutex_lock(&stm->link_mutex); + list_for_each_entry_safe(src, iter, &stm->link_list, link_entry) { + ret = __stm_source_link_drop(src, stm); + /* + * src <-> stm link must not change under the same + * stm::link_mutex, so complain loudly if it has; + * also in this situation ret!=0 means this src is + * not connected to this stm and it should be otherwise + * safe to proceed with the tear-down of stm. + */ + WARN_ON_ONCE(ret); + } + mutex_unlock(&stm->link_mutex); + + synchronize_srcu(&stm_source_srcu); + + unregister_chrdev(stm->major, stm_data->name); + + mutex_lock(&stm->policy_mutex); + if (stm->policy) + stp_policy_unbind(stm->policy); + mutex_unlock(&stm->policy_mutex); + + for (i = stm->data->sw_start; i <= stm->data->sw_end; i++) + stp_master_free(stm, i); + + device_unregister(&stm->dev); + stm_data->stm = NULL; +} +EXPORT_SYMBOL_GPL(stm_unregister_device); + +/* + * stm::link_list access serialization uses a spinlock and a mutex; holding + * either of them guarantees that the list is stable; modification requires + * holding both of them. + * + * Lock ordering is as follows: + * stm::link_mutex + * stm::link_lock + * src::link_lock + */ + +/** + * stm_source_link_add() - connect an stm_source device to an stm device + * @src: stm_source device + * @stm: stm device + * + * This function establishes a link from stm_source to an stm device so that + * the former can send out trace data to the latter. + * + * Return: 0 on success, -errno otherwise. + */ +static int stm_source_link_add(struct stm_source_device *src, + struct stm_device *stm) +{ + char *ids[] = { NULL, "default", NULL }; + int err = -ENOMEM; + + mutex_lock(&stm->link_mutex); + spin_lock(&stm->link_lock); + spin_lock(&src->link_lock); + + /* src->link is dereferenced under stm_source_srcu but not the list */ + rcu_assign_pointer(src->link, stm); + list_add_tail(&src->link_entry, &stm->link_list); + + spin_unlock(&src->link_lock); + spin_unlock(&stm->link_lock); + mutex_unlock(&stm->link_mutex); + + ids[0] = kstrdup(src->data->name, GFP_KERNEL); + if (!ids[0]) + goto fail_detach; + + err = stm_assign_first_policy(stm, &src->output, ids, + src->data->nr_chans); + kfree(ids[0]); + + if (err) + goto fail_detach; + + /* this is to notify the STM device that a new link has been made */ + if (stm->data->link) + err = stm->data->link(stm->data, src->output.master, + src->output.channel); + + if (err) + goto fail_free_output; + + /* this is to let the source carry out all necessary preparations */ + if (src->data->link) + src->data->link(src->data); + + return 0; + +fail_free_output: + stm_output_free(stm, &src->output); + +fail_detach: + mutex_lock(&stm->link_mutex); + spin_lock(&stm->link_lock); + spin_lock(&src->link_lock); + + rcu_assign_pointer(src->link, NULL); + list_del_init(&src->link_entry); + + spin_unlock(&src->link_lock); + spin_unlock(&stm->link_lock); + mutex_unlock(&stm->link_mutex); + + return err; +} + +/** + * __stm_source_link_drop() - detach stm_source from an stm device + * @src: stm_source device + * @stm: stm device + * + * If @stm is @src::link, disconnect them from one another and put the + * reference on the @stm device. + * + * Caller must hold stm::link_mutex. + */ +static int __stm_source_link_drop(struct stm_source_device *src, + struct stm_device *stm) +{ + struct stm_device *link; + int ret = 0; + + lockdep_assert_held(&stm->link_mutex); + + /* for stm::link_list modification, we hold both mutex and spinlock */ + spin_lock(&stm->link_lock); + spin_lock(&src->link_lock); + link = srcu_dereference_check(src->link, &stm_source_srcu, 1); + + /* + * The linked device may have changed since we last looked, because + * we weren't holding the src::link_lock back then; if this is the + * case, tell the caller to retry. + */ + if (link != stm) { + ret = -EAGAIN; + goto unlock; + } + + stm_output_free(link, &src->output); + list_del_init(&src->link_entry); + pm_runtime_mark_last_busy(&link->dev); + pm_runtime_put_autosuspend(&link->dev); + /* matches stm_find_device() from stm_source_link_store() */ + stm_put_device(link); + rcu_assign_pointer(src->link, NULL); + +unlock: + spin_unlock(&src->link_lock); + spin_unlock(&stm->link_lock); + + /* + * Call the unlink callbacks for both source and stm, when we know + * that we have actually performed the unlinking. + */ + if (!ret) { + if (src->data->unlink) + src->data->unlink(src->data); + + if (stm->data->unlink) + stm->data->unlink(stm->data, src->output.master, + src->output.channel); + } + + return ret; +} + +/** + * stm_source_link_drop() - detach stm_source from its stm device + * @src: stm_source device + * + * Unlinking means disconnecting from source's STM device; after this + * writes will be unsuccessful until it is linked to a new STM device. + * + * This will happen on "stm_source_link" sysfs attribute write to undo + * the existing link (if any), or on linked STM device's de-registration. + */ +static void stm_source_link_drop(struct stm_source_device *src) +{ + struct stm_device *stm; + int idx, ret; + +retry: + idx = srcu_read_lock(&stm_source_srcu); + /* + * The stm device will be valid for the duration of this + * read section, but the link may change before we grab + * the src::link_lock in __stm_source_link_drop(). + */ + stm = srcu_dereference(src->link, &stm_source_srcu); + + ret = 0; + if (stm) { + mutex_lock(&stm->link_mutex); + ret = __stm_source_link_drop(src, stm); + mutex_unlock(&stm->link_mutex); + } + + srcu_read_unlock(&stm_source_srcu, idx); + + /* if it did change, retry */ + if (ret == -EAGAIN) + goto retry; +} + +static ssize_t stm_source_link_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct stm_source_device *src = to_stm_source_device(dev); + struct stm_device *stm; + int idx, ret; + + idx = srcu_read_lock(&stm_source_srcu); + stm = srcu_dereference(src->link, &stm_source_srcu); + ret = sprintf(buf, "%s\n", + stm ? dev_name(&stm->dev) : "<none>"); + srcu_read_unlock(&stm_source_srcu, idx); + + return ret; +} + +static ssize_t stm_source_link_store(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t count) +{ + struct stm_source_device *src = to_stm_source_device(dev); + struct stm_device *link; + int err; + + stm_source_link_drop(src); + + link = stm_find_device(buf); + if (!link) + return -EINVAL; + + pm_runtime_get(&link->dev); + + err = stm_source_link_add(src, link); + if (err) { + pm_runtime_put_autosuspend(&link->dev); + /* matches the stm_find_device() above */ + stm_put_device(link); + } + + return err ? : count; +} + +static DEVICE_ATTR_RW(stm_source_link); + +static struct attribute *stm_source_attrs[] = { + &dev_attr_stm_source_link.attr, + NULL, +}; + +ATTRIBUTE_GROUPS(stm_source); + +static struct class stm_source_class = { + .name = "stm_source", + .dev_groups = stm_source_groups, +}; + +static void stm_source_device_release(struct device *dev) +{ + struct stm_source_device *src = to_stm_source_device(dev); + + kfree(src); +} + +/** + * stm_source_register_device() - register an stm_source device + * @parent: parent device + * @data: device description structure + * + * This will create a device of stm_source class that can write + * data to an stm device once linked. + * + * Return: 0 on success, -errno otherwise. + */ +int stm_source_register_device(struct device *parent, + struct stm_source_data *data) +{ + struct stm_source_device *src; + int err; + + if (!stm_core_up) + return -EPROBE_DEFER; + + src = kzalloc(sizeof(*src), GFP_KERNEL); + if (!src) + return -ENOMEM; + + device_initialize(&src->dev); + src->dev.class = &stm_source_class; + src->dev.parent = parent; + src->dev.release = stm_source_device_release; + + err = kobject_set_name(&src->dev.kobj, "%s", data->name); + if (err) + goto err; + + pm_runtime_no_callbacks(&src->dev); + pm_runtime_forbid(&src->dev); + + err = device_add(&src->dev); + if (err) + goto err; + + stm_output_init(&src->output); + spin_lock_init(&src->link_lock); + INIT_LIST_HEAD(&src->link_entry); + src->data = data; + data->src = src; + + return 0; + +err: + put_device(&src->dev); + + return err; +} +EXPORT_SYMBOL_GPL(stm_source_register_device); + +/** + * stm_source_unregister_device() - unregister an stm_source device + * @data: device description that was used to register the device + * + * This will remove a previously created stm_source device from the system. + */ +void stm_source_unregister_device(struct stm_source_data *data) +{ + struct stm_source_device *src = data->src; + + stm_source_link_drop(src); + + device_unregister(&src->dev); +} +EXPORT_SYMBOL_GPL(stm_source_unregister_device); + +int notrace stm_source_write(struct stm_source_data *data, + unsigned int chan, + const char *buf, size_t count) +{ + struct stm_source_device *src = data->src; + struct stm_device *stm; + int idx; + + if (!src->output.nr_chans) + return -ENODEV; + + if (chan >= src->output.nr_chans) + return -EINVAL; + + idx = srcu_read_lock(&stm_source_srcu); + + stm = srcu_dereference(src->link, &stm_source_srcu); + if (stm) + count = stm_write(stm, &src->output, chan, buf, count); + else + count = -ENODEV; + + srcu_read_unlock(&stm_source_srcu, idx); + + return count; +} +EXPORT_SYMBOL_GPL(stm_source_write); + +static int __init stm_core_init(void) +{ + int err; + + err = class_register(&stm_class); + if (err) + return err; + + err = class_register(&stm_source_class); + if (err) + goto err_stm; + + err = stp_configfs_init(); + if (err) + goto err_src; + + init_srcu_struct(&stm_source_srcu); + INIT_LIST_HEAD(&stm_pdrv_head); + mutex_init(&stm_pdrv_mutex); + + /* + * So as to not confuse existing users with a requirement + * to load yet another module, do it here. + */ + if (IS_ENABLED(CONFIG_STM_PROTO_BASIC)) + (void)request_module_nowait("stm_p_basic"); + stm_core_up++; + + return 0; + +err_src: + class_unregister(&stm_source_class); +err_stm: + class_unregister(&stm_class); + + return err; +} + +module_init(stm_core_init); + +static void __exit stm_core_exit(void) +{ + cleanup_srcu_struct(&stm_source_srcu); + class_unregister(&stm_source_class); + class_unregister(&stm_class); + stp_configfs_exit(); +} + +module_exit(stm_core_exit); + +MODULE_LICENSE("GPL v2"); +MODULE_DESCRIPTION("System Trace Module device class"); +MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>"); |