diff options
| -rw-r--r-- | Documentation/dma-buf-sync.txt | 290 | ||||
| -rw-r--r-- | drivers/base/Kconfig | 7 | ||||
| -rw-r--r-- | drivers/base/Makefile | 1 | ||||
| -rw-r--r-- | drivers/base/dma-buf.c | 4 | ||||
| -rw-r--r-- | drivers/base/dmabuf-sync.c | 674 | ||||
| -rw-r--r-- | include/linux/dma-buf.h | 16 | ||||
| -rw-r--r-- | include/linux/dmabuf-sync.h | 178 |
7 files changed, 1170 insertions, 0 deletions
diff --git a/Documentation/dma-buf-sync.txt b/Documentation/dma-buf-sync.txt new file mode 100644 index 00000000000..442775995ee --- /dev/null +++ b/Documentation/dma-buf-sync.txt @@ -0,0 +1,290 @@ + DMA Buffer Synchronization Framework + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + + Inki Dae + <inki dot dae at samsung dot com> + <daeinki at gmail dot com> + +This document is a guide for device-driver writers describing the DMA buffer +synchronization API. This document also describes how to use the API to +use buffer synchronization mechanism between DMA and DMA, CPU and DMA, and +CPU and CPU. + +The DMA Buffer synchronization API provides buffer synchronization mechanism; +i.e., buffer access control to CPU and DMA, and easy-to-use interfaces for +device drivers and user application. And this API can be used for all dma +devices using system memory as dma buffer, especially for most ARM based SoCs. + + +Motivation +---------- + +Buffer synchronization issue between DMA and DMA: + Sharing a buffer, a device cannot be aware of when the other device + will access the shared buffer: a device may access a buffer containing + wrong data if the device accesses the shared buffer while another + device is still accessing the shared buffer. + Therefore, a user process should have waited for the completion of DMA + access by another device before a device tries to access the shared + buffer. + +Buffer synchronization issue between CPU and DMA: + A user process should consider that when having to send a buffer, filled + by CPU, to a device driver for the device driver to access the buffer as + a input buffer while CPU and DMA are sharing the buffer. + This means that the user process needs to understand how the device + driver is worked. Hence, the conventional mechanism not only makes + user application complicated but also incurs performance overhead. + +Buffer synchronization issue between CPU and CPU: + In case that two processes share one buffer; shared with DMA also, + they may need some mechanism to allow process B to access the shared + buffer after the completion of CPU access by process A. + Therefore, process B should have waited for the completion of CPU access + by process A using the mechanism before trying to access the shared + buffer. + +What is the best way to solve these buffer synchronization issues? + We may need a common object that a device driver and a user process + notify the common object of when they try to access a shared buffer. + That way we could decide when we have to allow or not to allow for CPU + or DMA to access the shared buffer through the common object. + If so, what could become the common object? Right, that's a dma-buf[1]. + Now we have already been using the dma-buf to share one buffer with + other drivers. + +How we can utilize multi threads for more performance? + DMA and CPU works individually. So CPU could perform other works while + DMA are performing some works, and vise versa. + However, in the conventional way, that is not easy to do so because + DMA operation is depend on CPU operation, and vice versa. + + Conventional way: + User Kernel + --------------------------------------------------------------------- + CPU writes something to src + send the src to driver-------------------------> + update DMA register + request DMA start(1)---------------------------> + DMA start + <---------completion signal(2)---------- + CPU accesses dst + + (1) Request DMA start after the CPU access to src buffer is completed. + (2) Access dst buffer after DMA access to the dst buffer is completed. + +On the other hand, if there is something to control buffer access between CPU +and DMA? The below shows that: + + User(thread a) User(thread b) Kernel + --------------------------------------------------------------------- + send a src to driver----------------------------------> + update DMA register + lock the src + request DMA start(1)----------> + CPU acccess to src + unlock the src lock src and dst + DMA start + <-------------completion signal(2)------------- + lock dst DMA completion + CPU access to dst unlock src and dst + unlock DST + + (1) Try to start DMA operation while CPU is accessing the src buffer. + (2) Try CPU access to dst buffer while DMA is accessing the dst buffer. + + In the same way, we could reduce hand shaking overhead between + two processes when those processes need to share a shared buffer. + There may be other cases that we could reduce overhead as well. + + +Basic concept +------------- + +The mechanism of this framework has the following steps, + 1. Register dmabufs to a sync object - A task gets a new sync object and + can add one or more dmabufs that the task wants to access. + This registering should be performed when a device context or an event + context such as a page flip event is created or before CPU accesses a shared + buffer. + + dma_buf_sync_get(a sync object, a dmabuf); + + 2. Lock a sync object - A task tries to lock all dmabufs added in its own + sync object. Basically, the lock mechanism uses ww-mutexes[2] to avoid dead + lock issue and for race condition between CPU and CPU, CPU and DMA, and DMA + and DMA. Taking a lock means that others cannot access all locked dmabufs + until the task that locked the corresponding dmabufs, unlocks all the locked + dmabufs. + This locking should be performed before DMA or CPU accesses these dmabufs. + + dma_buf_sync_lock(a sync object); + + 3. Unlock a sync object - The task unlocks all dmabufs added in its own sync + object. The unlock means that the DMA or CPU accesses to the dmabufs have + been completed so that others may access them. + This unlocking should be performed after DMA or CPU has completed accesses + to the dmabufs. + + dma_buf_sync_unlock(a sync object); + + 4. Unregister one or all dmabufs from a sync object - A task unregisters + the given dmabufs from the sync object. This means that the task dosen't + want to lock the dmabufs. + The unregistering should be performed after DMA or CPU has completed + accesses to the dmabufs or when dma_buf_sync_lock() is failed. + + dma_buf_sync_put(a sync object, a dmabuf); + dma_buf_sync_put_all(a sync object); + + The described steps may be summarized as: + get -> lock -> CPU or DMA access to a buffer/s -> unlock -> put + +This framework includes the following two features. + 1. read (shared) and write (exclusive) locks - A task is required to declare + the access type when the task tries to register a dmabuf; + READ, WRITE, READ DMA, or WRITE DMA. + + The below is example codes, + struct dmabuf_sync *sync; + + sync = dmabuf_sync_init(NULL, "test sync"); + + dmabuf_sync_get(sync, dmabuf, DMA_BUF_ACCESS_R); + ... + + 2. Mandatory resource releasing - a task cannot hold a lock indefinitely. + A task may never try to unlock a buffer after taking a lock to the buffer. + In this case, a timer handler to the corresponding sync object is called + in five (default) seconds and then the timed-out buffer is unlocked by work + queue handler to avoid lockups and to enforce resources of the buffer. + + +Access types +------------ + +DMA_BUF_ACCESS_R - CPU will access a buffer for read. +DMA_BUF_ACCESS_W - CPU will access a buffer for read or write. +DMA_BUF_ACCESS_DMA_R - DMA will access a buffer for read +DMA_BUF_ACCESS_DMA_W - DMA will access a buffer for read or write. + + +Generic user interfaces +----------------------- + +And this framework includes fcntl system call[3] as interfaces exported +to user. As you know, user sees a buffer object as a dma-buf file descriptor. +So fcntl() call with the file descriptor means to lock some buffer region being +managed by the dma-buf object. + + +API set +------- + +bool is_dmabuf_sync_supported(void) + - Check if dmabuf sync is supported or not. + +struct dmabuf_sync *dmabuf_sync_init(void *priv, const char *name) + - Allocate and initialize a new sync object. The caller can get a new + sync object for buffer synchronization. priv is used to set caller's + private data and name is the name of sync object. + +void dmabuf_sync_fini(struct dmabuf_sync *sync) + - Release all resources to the sync object. + +int dmabuf_sync_get(struct dmabuf_sync *sync, void *sync_buf, + unsigned int type) + - Get dmabuf sync object. Internally, this function allocates + a dmabuf_sync object and adds a given dmabuf to it, and also takes + a reference to the dmabuf. The caller can tie up multiple dmabufs + into one sync object by calling this function several times. + +void dmabuf_sync_put(struct dmabuf_sync *sync, struct dma_buf *dmabuf) + - Put dmabuf sync object to a given dmabuf. Internally, this function + removes a given dmabuf from a sync object and remove the sync object. + At this time, the dmabuf is putted. + +void dmabuf_sync_put_all(struct dmabuf_sync *sync) + - Put dmabuf sync object to dmabufs. Internally, this function removes + all dmabufs from a sync object and remove the sync object. + At this time, all dmabufs are putted. + +int dmabuf_sync_lock(struct dmabuf_sync *sync) + - Lock all dmabufs added in a sync object. The caller should call this + function prior to CPU or DMA access to the dmabufs so that others can + not access the dmabufs. Internally, this function avoids dead lock + issue with ww-mutexes. + +int dmabuf_sync_single_lock(struct dma_buf *dmabuf) + - Lock a dmabuf. The caller should call this + function prior to CPU or DMA access to the dmabuf so that others can + not access the dmabuf. + +int dmabuf_sync_unlock(struct dmabuf_sync *sync) + - Unlock all dmabufs added in a sync object. The caller should call + this function after CPU or DMA access to the dmabufs is completed so + that others can access the dmabufs. + +void dmabuf_sync_single_unlock(struct dma_buf *dmabuf) + - Unlock a dmabuf. The caller should call this function after CPU or + DMA access to the dmabuf is completed so that others can access + the dmabuf. + + +Tutorial for device driver +-------------------------- + +1. Allocate and Initialize a sync object: + struct dmabuf_sync *sync; + + sync = dmabuf_sync_init(NULL, "test sync"); + ... + +2. Add a dmabuf to the sync object when setting up dma buffer relevant registers: + dmabuf_sync_get(sync, dmabuf, DMA_BUF_ACCESS_READ); + ... + +3. Lock all dmabufs of the sync object before DMA or CPU accesses the dmabufs: + dmabuf_sync_lock(sync); + ... + +4. Now CPU or DMA can access all dmabufs locked in step 3. + +5. Unlock all dmabufs added in a sync object after DMA or CPU access to these + dmabufs is completed: + dmabuf_sync_unlock(sync); + + And call the following functions to release all resources, + dmabuf_sync_put_all(sync); + dmabuf_sync_fini(sync); + + +Tutorial for user application +----------------------------- + struct flock filelock; + +1. Lock a dma buf: + filelock.l_type = F_WRLCK or F_RDLCK; + + /* lock entire region to the dma buf. */ + filelock.lwhence = SEEK_CUR; + filelock.l_start = 0; + filelock.l_len = 0; + + fcntl(dmabuf fd, F_SETLKW or F_SETLK, &filelock); + ... + CPU access to the dma buf + +2. Unlock a dma buf: + filelock.l_type = F_UNLCK; + + fcntl(dmabuf fd, F_SETLKW or F_SETLK, &filelock); + + close(dmabuf fd) call would also unlock the dma buf. And for more + detail, please refer to [3] + + +References: +[1] http://lwn.net/Articles/470339/ +[2] https://patchwork.kernel.org/patch/2625361/ +[3] http://linux.die.net/man/2/fcntl diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig index 07abd9d76f7..eb894217bd7 100644 --- a/drivers/base/Kconfig +++ b/drivers/base/Kconfig @@ -202,6 +202,13 @@ config DMA_SHARED_BUFFER APIs extension; the file's descriptor can then be passed on to other driver. +config DMABUF_SYNC + bool "DMABUF Synchronization Framework" + depends on DMA_SHARED_BUFFER + help + This option enables dmabuf sync framework for buffer synchronization between + DMA and DMA, CPU and DMA, and CPU and CPU. + config CMA bool "Contiguous Memory Allocator" depends on HAVE_DMA_CONTIGUOUS && HAVE_MEMBLOCK diff --git a/drivers/base/Makefile b/drivers/base/Makefile index 4e22ce3ed73..548d434c496 100644 --- a/drivers/base/Makefile +++ b/drivers/base/Makefile @@ -11,6 +11,7 @@ obj-y += power/ obj-$(CONFIG_HAS_DMA) += dma-mapping.o obj-$(CONFIG_HAVE_GENERIC_DMA_COHERENT) += dma-coherent.o obj-$(CONFIG_DMA_SHARED_BUFFER) += dma-buf.o +obj-$(CONFIG_DMABUF_SYNC) += dmabuf-sync.o obj-$(CONFIG_ISA) += isa.o obj-$(CONFIG_FW_LOADER) += firmware_class.o obj-$(CONFIG_NUMA) += node.o diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c index 08fe897c0b4..9a26981a688 100644 --- a/drivers/base/dma-buf.c +++ b/drivers/base/dma-buf.c @@ -29,6 +29,7 @@ #include <linux/export.h> #include <linux/debugfs.h> #include <linux/seq_file.h> +#include <linux/dmabuf-sync.h> static inline int is_dma_buf_file(struct file *); @@ -56,6 +57,8 @@ static int dma_buf_release(struct inode *inode, struct file *file) list_del(&dmabuf->list_node); mutex_unlock(&db_list.lock); + dmabuf_sync_reservation_fini(dmabuf); + kfree(dmabuf); return 0; } @@ -134,6 +137,7 @@ struct dma_buf *dma_buf_export_named(void *priv, const struct dma_buf_ops *ops, file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf, flags); + dmabuf_sync_reservation_init(dmabuf); dmabuf->file = file; mutex_init(&dmabuf->lock); diff --git a/drivers/base/dmabuf-sync.c b/drivers/base/dmabuf-sync.c new file mode 100644 index 00000000000..0b831118c79 --- /dev/null +++ b/drivers/base/dmabuf-sync.c @@ -0,0 +1,674 @@ +/* + * Copyright (C) 2013 Samsung Electronics Co.Ltd + * Authors: + * Inki Dae <inki.dae@samsung.com> + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License as published by the + * Free Software Foundation; either version 2 of the License, or (at your + * option) any later version. + * + */ + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/debugfs.h> +#include <linux/uaccess.h> + +#include <linux/dmabuf-sync.h> + +#define MAX_SYNC_TIMEOUT 5 /* Second. */ + +int dmabuf_sync_enabled = 1; + +MODULE_PARM_DESC(enabled, "Check if dmabuf sync is supported or not"); +module_param_named(enabled, dmabuf_sync_enabled, int, 0444); + +DEFINE_WW_CLASS(dmabuf_sync_ww_class); +EXPORT_SYMBOL(dmabuf_sync_ww_class); + +static void dmabuf_sync_timeout_worker(struct work_struct *work) +{ + struct dmabuf_sync *sync = container_of(work, struct dmabuf_sync, work); + struct dmabuf_sync_object *sobj; + + mutex_lock(&sync->lock); + + list_for_each_entry(sobj, &sync->syncs, head) { + if (WARN_ON(!sobj->robj)) + continue; + + mutex_lock(&sobj->robj->lock); + + printk(KERN_WARNING "%s: timeout = 0x%x [type = %d, " \ + "refcnt = %d, locked = %d]\n", + sync->name, (u32)sobj->dmabuf, + sobj->access_type, + atomic_read(&sobj->robj->shared_cnt), + sobj->robj->locked); + + /* unlock only valid sync object. */ + if (!sobj->robj->locked) { + mutex_unlock(&sobj->robj->lock); + continue; + } + + if (sobj->robj->shared && + atomic_add_unless(&sobj->robj->shared_cnt, -1, 1)) { + mutex_unlock(&sobj->robj->lock); + continue; + } + + mutex_unlock(&sobj->robj->lock); + + ww_mutex_unlock(&sobj->robj->sync_lock); + + mutex_lock(&sobj->robj->lock); + + if (sobj->access_type & DMA_BUF_ACCESS_R) + printk(KERN_WARNING "%s: r-unlocked = 0x%x\n", + sync->name, (u32)sobj->dmabuf); + else + printk(KERN_WARNING "%s: w-unlocked = 0x%x\n", + sync->name, (u32)sobj->dmabuf); + + mutex_unlock(&sobj->robj->lock); + } + + sync->status = 0; + mutex_unlock(&sync->lock); + + dmabuf_sync_put_all(sync); + dmabuf_sync_fini(sync); +} + +static void dmabuf_sync_lock_timeout(unsigned long arg) +{ + struct dmabuf_sync *sync = (struct dmabuf_sync *)arg; + + schedule_work(&sync->work); +} + +static int dmabuf_sync_lock_objs(struct dmabuf_sync *sync, + struct ww_acquire_ctx *ctx) +{ + struct dmabuf_sync_object *contended_sobj = NULL; + struct dmabuf_sync_object *res_sobj = NULL; + struct dmabuf_sync_object *sobj = NULL; + int ret; + + if (ctx) + ww_acquire_init(ctx, &dmabuf_sync_ww_class); + +retry: + list_for_each_entry(sobj, &sync->syncs, head) { + if (WARN_ON(!sobj->robj)) + continue; + + mutex_lock(&sobj->robj->lock); + + /* Don't lock in case of read and read. */ + if (sobj->robj->accessed_type & DMA_BUF_ACCESS_R && + sobj->access_type & DMA_BUF_ACCESS_R) { + atomic_inc(&sobj->robj->shared_cnt); + sobj->robj->shared = true; + mutex_unlock(&sobj->robj->lock); + continue; + } + + if (sobj == res_sobj) { + res_sobj = NULL; + mutex_unlock(&sobj->robj->lock); + continue; + } + + mutex_unlock(&sobj->robj->lock); + + ret = ww_mutex_lock(&sobj->robj->sync_lock, ctx); + if (ret < 0) { + contended_sobj = sobj; + + if (ret == -EDEADLK) + printk(KERN_WARNING"%s: deadlock = 0x%x\n", + sync->name, (u32)sobj->dmabuf); + goto err; + } + + mutex_lock(&sobj->robj->lock); + sobj->robj->locked = true; + + mutex_unlock(&sobj->robj->lock); + } + + if (ctx) + ww_acquire_done(ctx); + + init_timer(&sync->timer); + + sync->timer.data = (unsigned long)sync; + sync->timer.function = dmabuf_sync_lock_timeout; + sync->timer.expires = jiffies + (HZ * MAX_SYNC_TIMEOUT); + + add_timer(&sync->timer); + + return 0; + +err: + list_for_each_entry_continue_reverse(sobj, &sync->syncs, head) { + mutex_lock(&sobj->robj->lock); + + /* Don't need to unlock in case of read and read. */ + if (atomic_add_unless(&sobj->robj->shared_cnt, -1, 1)) { + mutex_unlock(&sobj->robj->lock); + continue; + } + + ww_mutex_unlock(&sobj->robj->sync_lock); + sobj->robj->locked = false; + + mutex_unlock(&sobj->robj->lock); + } + + if (res_sobj) { + mutex_lock(&res_sobj->robj->lock); + + if (!atomic_add_unless(&res_sobj->robj->shared_cnt, -1, 1)) { + ww_mutex_unlock(&res_sobj->robj->sync_lock); + res_sobj->robj->locked = false; + } + + mutex_unlock(&res_sobj->robj->lock); + } + + if (ret == -EDEADLK) { + ww_mutex_lock_slow(&contended_sobj->robj->sync_lock, ctx); + res_sobj = contended_sobj; + + goto retry; + } + + if (ctx) + ww_acquire_fini(ctx); + + return ret; +} + +static void dmabuf_sync_unlock_objs(struct dmabuf_sync *sync, + struct ww_acquire_ctx *ctx) +{ + struct dmabuf_sync_object *sobj; + + if (list_empty(&sync->syncs)) + return; + + mutex_lock(&sync->lock); + + list_for_each_entry(sobj, &sync->syncs, head) { + mutex_lock(&sobj->robj->lock); + + if (sobj->robj->shared) { + if (atomic_add_unless(&sobj->robj->shared_cnt, -1, + 1)) { + mutex_unlock(&sobj->robj->lock); + continue; + } + + mutex_unlock(&sobj->robj->lock); + + ww_mutex_unlock(&sobj->robj->sync_lock); + + mutex_lock(&sobj->robj->lock); + sobj->robj->shared = false; + sobj->robj->locked = false; + } else { + mutex_unlock(&sobj->robj->lock); + + ww_mutex_unlock(&sobj->robj->sync_lock); + + mutex_lock(&sobj->robj->lock); + sobj->robj->locked = false; + } + + mutex_unlock(&sobj->robj->lock); + } + + mutex_unlock(&sync->lock); + + if (ctx) + ww_acquire_fini(ctx); + + del_timer(&sync->timer); +} + +/** + * is_dmabuf_sync_supported - Check if dmabuf sync is supported or not. + */ +bool is_dmabuf_sync_supported(void) +{ + return dmabuf_sync_enabled == 1; +} +EXPORT_SYMBOL(is_dmabuf_sync_supported); + +/** + * dmabuf_sync_init - Allocate and initialize a dmabuf sync. + * + * @priv: A device private data. + * @name: A sync object name. + * + * This function should be called when a device context or an event + * context such as a page flip event is created. And the created + * dmabuf_sync object should be set to the context. + * The caller can get a new sync object for buffer synchronization + * through this function. + */ +struct dmabuf_sync *dmabuf_sync_init(void *priv, const char *name) +{ + struct dmabuf_sync *sync; + + sync = kzalloc(sizeof(*sync), GFP_KERNEL); + if (!sync) + return ERR_PTR(-ENOMEM); + + strncpy(sync->name, name, ARRAY_SIZE(sync->name) - 1); + + sync->priv = priv; + INIT_LIST_HEAD(&sync->syncs); + mutex_init(&sync->lock); + INIT_WORK(&sync->work, dmabuf_sync_timeout_worker); + + return sync; +} +EXPORT_SYMBOL(dmabuf_sync_init); + +/** + * dmabuf_sync_fini - Release a given dmabuf sync. + * + * @sync: An object to dmabuf_sync structure. + * + * This function should be called if some operation is failed after + * dmabuf_sync_init call to release relevant resources, and after + * dmabuf_sync_unlock function is called. + */ +void dmabuf_sync_fini(struct dmabuf_sync *sync) +{ + if (WARN_ON(!sync)) + return; + + kfree(sync); +} +EXPORT_SYMBOL(dmabuf_sync_fini); + +/* + * dmabuf_sync_get_obj - Add a given object to syncs list. + * + * @sync: An object to dmabuf_sync structure. + * @dmabuf: An object to dma_buf structure. + * @type: A access type to a dma buf. + * The DMA_BUF_ACCESS_R means that this dmabuf could be accessed by + * others for read access. On the other hand, the DMA_BUF_ACCESS_W + * means that this dmabuf couldn't be accessed by others but would be + * accessed by caller's dma exclusively. And the DMA_BUF_ACCESS_DMA can be + * combined. + * + * This function creates and initializes a new dmabuf sync object and it adds + * the dmabuf sync object to syncs list to track and manage all dmabufs. + */ +static int dmabuf_sync_get_obj(struct dmabuf_sync *sync, struct dma_buf *dmabuf, + unsigned int type) +{ + struct dmabuf_sync_object *sobj; + + if (!dmabuf->sync) { + WARN_ON(1); + return -EFAULT; + } + + if (!IS_VALID_DMA_BUF_ACCESS_TYPE(type)) + return -EINVAL; + + if ((type & DMA_BUF_ACCESS_RW) == DMA_BUF_ACCESS_RW) + type &= ~DMA_BUF_ACCESS_R; + + sobj = kzalloc(sizeof(*sobj), GFP_KERNEL); + if (!sobj) { + WARN_ON(1); + return -ENOMEM; + } + + sobj->dmabuf = dmabuf; + sobj->robj = dmabuf->sync; + + mutex_lock(&sync->lock); + list_add_tail(&sobj->head, &sync->syncs); + mutex_unlock(&sync->lock); + + get_dma_buf(dmabuf); + + mutex_lock(&sobj->robj->lock); + sobj->access_type = type; + mutex_unlock(&sobj->robj->lock); + + return 0; +} + +/* + * dmabuf_sync_put_obj - Release a given sync object. + * + * @sync: An object to dmabuf_sync structure. + * + * This function should be called if some operation is failed after + * dmabuf_sync_get_obj call to release a given sync object. + */ +static void dmabuf_sync_put_obj(struct dmabuf_sync *sync, + struct dma_buf *dmabuf) +{ + struct dmabuf_sync_object *sobj; + + mutex_lock(&sync->lock); + + list_for_each_entry(sobj, &sync->syncs, head) { + if (sobj->dmabuf != dmabuf) + continue; + + dma_buf_put(sobj->dmabuf); + + list_del_init(&sobj->head); + kfree(sobj); + break; + } + + if (list_empty(&sync->syncs)) + sync->status = 0; + + mutex_unlock(&sync->lock); +} + +/* + * dmabuf_sync_put_objs - Release all sync objects of dmabuf_sync. + * + * @sync: An object to dmabuf_sync structure. + * + * This function should be called if some operation is failed after + * dmabuf_sync_get_obj call to release all sync objects. + */ +static void dmabuf_sync_put_objs(struct dmabuf_sync *sync) +{ + struct dmabuf_sync_object *sobj, *next; + + mutex_lock(&sync->lock); + + list_for_each_entry_safe(sobj, next, &sync->syncs, head) { + dma_buf_put(sobj->dmabuf); + + list_del_init(&sobj->head); + kfree(sobj); + } + + mutex_unlock(&sync->lock); + + sync->status = 0; +} + +/** + * dmabuf_sync_lock - lock all dmabufs added to syncs list. + * + * @sync: An object to dmabuf_sync structure. + * + * The caller should call this function prior to CPU or DMA access to + * the dmabufs so that others can not access the dmabufs. + * Internally, this function avoids dead lock issue with ww-mutex. + */ +int dmabuf_sync_lock(struct dmabuf_sync *sync) +{ + int ret; + + if (!sync) { + WARN_ON(1); + return -EFAULT; + } + + if (list_empty(&sync->syncs)) + return -EINVAL; + + if (sync->status != DMABUF_SYNC_GOT) + return -EINVAL; + + ret = dmabuf_sync_lock_objs(sync, &sync->ctx); + if (ret < 0) { + WARN_ON(1); + return ret; + } + + sync->status = DMABUF_SYNC_LOCKED; + + return ret; +} +EXPORT_SYMBOL(dmabuf_sync_lock); + +/** + * dmabuf_sync_unlock - unlock all objects added to syncs list. + * + * @sync: An object to dmabuf_sync structure. + * + * The caller should call this function after CPU or DMA access to + * the dmabufs is completed so that others can access the dmabufs. + */ +int dmabuf_sync_unlock(struct dmabuf_sync *sync) +{ + if (!sync) { + WARN_ON(1); + return -EFAULT; + } + + /* If current dmabuf sync object wasn't reserved then just return. */ + if (sync->status != DMABUF_SYNC_LOCKED) + return -EAGAIN; + + dmabuf_sync_unlock_objs(sync, &sync->ctx); + + return 0; +} +EXPORT_SYMBOL(dmabuf_sync_unlock); + +/** + * dmabuf_sync_single_lock - lock a dma buf. + * + * @dmabuf: A dma buf object that tries to lock. + * @type: A access type to a dma buf. + * The DMA_BUF_ACCESS_R means that this dmabuf could be accessed by + * others for read access. On the other hand, the DMA_BUF_ACCESS_W + * means that this dmabuf couldn't be accessed by others but would be + * accessed by caller's dma exclusively. And the DMA_BUF_ACCESS_DMA can + * be combined with other. + * @wait: Indicate whether caller is blocked or not. + * true means that caller will be blocked, and false means that this + * function will return -EAGAIN if this caller can't take the lock + * right now. + * + * The caller should call this function prior to CPU or DMA access to the dmabuf + * so that others cannot access the dmabuf. + */ +int dmabuf_sync_single_lock(struct dma_buf *dmabuf, unsigned int type, + bool wait) +{ + struct dmabuf_sync_reservation *robj; + + if (!dmabuf->sync) { + WARN_ON(1); + return -EFAULT; + } + + if (!IS_VALID_DMA_BUF_ACCESS_TYPE(type)) { + WARN_ON(1); + return -EINVAL; + } + + get_dma_buf(dmabuf); + robj = dmabuf->sync; + + mutex_lock(&robj->lock); + + /* Don't lock in case of read and read. */ + if (robj->accessed_type & DMA_BUF_ACCESS_R && type & DMA_BUF_ACCESS_R) { + atomic_inc(&robj->shared_cnt); + robj->shared = true; + mutex_unlock(&robj->lock); + return 0; + } + + /* + * In case of F_SETLK, just return -EAGAIN if this dmabuf has already + * been locked. + */ + if (!wait && robj->locked) { + mutex_unlock(&robj->lock); + dma_buf_put(dmabuf); + return -EAGAIN; + } + + mutex_unlock(&robj->lock); + + mutex_lock(&robj->sync_lock.base); + + mutex_lock(&robj->lock); + robj->locked = true; + mutex_unlock(&robj->lock); + + return 0; +} +EXPORT_SYMBOL(dmabuf_sync_single_lock); + +/** + * dmabuf_sync_single_unlock - unlock a dma buf. + * + * @dmabuf: A dma buf object that tries to unlock. + * + * The caller should call this function after CPU or DMA access to + * the dmabuf is completed so that others can access the dmabuf. + */ +void dmabuf_sync_single_unlock(struct dma_buf *dmabuf) +{ + struct dmabuf_sync_reservation *robj; + + if (!dmabuf->sync) { + WARN_ON(1); + return; + } + + robj = dmabuf->sync; + + mutex_lock(&robj->lock); + + if (robj->shared) { + if (atomic_add_unless(&robj->shared_cnt, -1 , 1)) { + mutex_unlock(&robj->lock); + return; + } + + robj->shared = false; + } + + mutex_unlock(&robj->lock); + + mutex_unlock(&robj->sync_lock.base); + + mutex_lock(&robj->lock); + robj->locked = false; + mutex_unlock(&robj->lock); + + dma_buf_put(dmabuf); + + return; +} +EXPORT_SYMBOL(dmabuf_sync_single_unlock); + +/** + * dmabuf_sync_get - Get dmabuf sync object. + * + * @sync: An object to dmabuf_sync structure. + * @sync_buf: A dmabuf object to be synchronized with others. + * @type: A access type to a dma buf. + * The DMA_BUF_ACCESS_R means that this dmabuf could be accessed by + * others for read access. On the other hand, the DMA_BUF_ACCESS_W + * means that this dmabuf couldn't be accessed by others but would be + * accessed by caller's dma exclusively. And the DMA_BUF_ACCESS_DMA can + * be combined with other. + * + * This function should be called after dmabuf_sync_init function is called. + * The caller can tie up multiple dmabufs into one sync object by calling this + * function several times. Internally, this function allocates + * a dmabuf_sync_object and adds a given dmabuf to it, and also takes + * a reference to a dmabuf. + */ +int dmabuf_sync_get(struct dmabuf_sync *sync, void *sync_buf, unsigned int type) +{ + int ret; + + if (!sync || !sync_buf) { + WARN_ON(1); + return -EFAULT; + } + + ret = dmabuf_sync_get_obj(sync, sync_buf, type); + if (ret < 0) { + WARN_ON(1); + return ret; + } + + sync->status = DMABUF_SYNC_GOT; + + return 0; +} +EXPORT_SYMBOL(dmabuf_sync_get); + +/** + * dmabuf_sync_put - Put dmabuf sync object to a given dmabuf. + * + * @sync: An object to dmabuf_sync structure. + * @dmabuf: An dmabuf object. + * + * This function should be called if some operation is failed after + * dmabuf_sync_get function is called to release the dmabuf, or + * dmabuf_sync_unlock function is called. Internally, this function + * removes a given dmabuf from a sync object and remove the sync object. + * At this time, the dmabuf is putted. + */ +void dmabuf_sync_put(struct dmabuf_sync *sync, struct dma_buf *dmabuf) +{ + if (!sync || !dmabuf) { + WARN_ON(1); + return; + } + + if (list_empty(&sync->syncs)) + return; + + dmabuf_sync_put_obj(sync, dmabuf); +} +EXPORT_SYMBOL(dmabuf_sync_put); + +/** + * dmabuf_sync_put_all - Put dmabuf sync object to dmabufs. + * + * @sync: An object to dmabuf_sync structure. + * + * This function should be called if some operation is failed after + * dmabuf_sync_get function is called to release all sync objects, or + * dmabuf_sync_unlock function is called. Internally, this function + * removes dmabufs from a sync object and remove the sync object. + * At this time, all dmabufs are putted. + */ +void dmabuf_sync_put_all(struct dmabuf_sync *sync) +{ + if (!sync) { + WARN_ON(1); + return; + } + + if (list_empty(&sync->syncs)) + return; + + dmabuf_sync_put_objs(sync); +} +EXPORT_SYMBOL(dmabuf_sync_put_all); diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index dfac5ed3112..01096736d17 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -115,6 +115,7 @@ struct dma_buf_ops { * @exp_name: name of the exporter; useful for debugging. * @list_node: node for dma_buf accounting and debugging. * @priv: exporter specific private data for this buffer object. + * @sync: sync object linked to this dma-buf */ struct dma_buf { size_t size; @@ -128,6 +129,7 @@ struct dma_buf { const char *exp_name; struct list_head list_node; void *priv; + void *sync; }; /** @@ -148,6 +150,20 @@ struct dma_buf_attachment { void *priv; }; +#define DMA_BUF_ACCESS_R 0x1 +#define DMA_BUF_ACCESS_W 0x2 +#define DMA_BUF_ACCESS_DMA 0x4 +#define DMA_BUF_ACCESS_RW (DMA_BUF_ACCESS_R | DMA_BUF_ACCESS_W) +#define DMA_BUF_ACCESS_DMA_R (DMA_BUF_ACCESS_R | DMA_BUF_ACCESS_DMA) +#define DMA_BUF_ACCESS_DMA_W (DMA_BUF_ACCESS_W | DMA_BUF_ACCESS_DMA) +#define DMA_BUF_ACCESS_DMA_RW (DMA_BUF_ACCESS_DMA_R | DMA_BUF_ACCESS_DMA_W) +#define IS_VALID_DMA_BUF_ACCESS_TYPE(t) (t == DMA_BUF_ACCESS_R || \ + t == DMA_BUF_ACCESS_W || \ + t == DMA_BUF_ACCESS_DMA_R || \ + t == DMA_BUF_ACCESS_DMA_W || \ + t == DMA_BUF_ACCESS_RW || \ + t == DMA_BUF_ACCESS_DMA_RW) + /** * get_dma_buf - convenience wrapper for get_file. * @dmabuf: [in] pointer to dma_buf diff --git a/include/linux/dmabuf-sync.h b/include/linux/dmabuf-sync.h new file mode 100644 index 00000000000..2502ad61a69 --- /dev/null +++ b/include/linux/dmabuf-sync.h @@ -0,0 +1,178 @@ +/* + * Copyright (C) 2013 Samsung Electronics Co.Ltd + * Authors: + * Inki Dae <inki.dae@samsung.com> + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License as published by the + * Free Software Foundation; either version 2 of the License, or (at your + * option) any later version. + * + */ + +#include <linux/mutex.h> +#include <linux/sched.h> +#include <linux/dma-buf.h> + +enum dmabuf_sync_status { + DMABUF_SYNC_GOT = 1, + DMABUF_SYNC_LOCKED, +}; + +struct dmabuf_sync_reservation { + struct ww_mutex sync_lock; + struct mutex lock; + atomic_t shared_cnt; + unsigned int accessed_type; + unsigned int shared; + unsigned int locked; +}; + +/* + * A structure for dmabuf_sync_object. + * + * @head: A list head to be added to syncs list. + * @robj: A reservation_object object. + * @dma_buf: A dma_buf object. + * @access_type: Indicate how a current task tries to access + * a given buffer. + */ +struct dmabuf_sync_object { + struct list_head head; + struct dmabuf_sync_reservation *robj; + struct dma_buf *dmabuf; + unsigned int access_type; +}; + +/* + * A structure for dmabuf_sync. + * + * @syncs: A list head to sync object and this is global to system. + * @list: A list entry used as committed list node + * @lock: A mutex lock to current sync object. + * @ctx: A current context for ww mutex. + * @work: A work struct to release resources at timeout. + * @priv: A private data. + * @name: A string to dmabuf sync owner. + * @timer: A timer list to avoid lockup and release resources. + * @status: Indicate current status (DMABUF_SYNC_GOT or DMABUF_SYNC_LOCKED). + */ +struct dmabuf_sync { + struct list_head syncs; + struct list_head list; + struct mutex lock; + struct ww_acquire_ctx ctx; + struct work_struct work; + void *priv; + char name[64]; + struct timer_list timer; + unsigned int status; +}; + +#ifdef CONFIG_DMABUF_SYNC + +extern struct ww_class dmabuf_sync_ww_class; + +static inline void dmabuf_sync_reservation_init(struct dma_buf *dmabuf) +{ + struct dmabuf_sync_reservation *obj; + + obj = kzalloc(sizeof(*obj), GFP_KERNEL); + if (!obj) + return; + + dmabuf->sync = obj; + + ww_mutex_init(&obj->sync_lock, &dmabuf_sync_ww_class); + + mutex_init(&obj->lock); + atomic_set(&obj->shared_cnt, 1); +} + +static inline void dmabuf_sync_reservation_fini(struct dma_buf *dmabuf) +{ + struct dmabuf_sync_reservation *obj; + + if (!dmabuf->sync) + return; + + obj = dmabuf->sync; + + ww_mutex_destroy(&obj->sync_lock); + + kfree(obj); +} + +extern bool is_dmabuf_sync_supported(void); + +extern struct dmabuf_sync *dmabuf_sync_init(void *priv, const char *name); + +extern void dmabuf_sync_fini(struct dmabuf_sync *sync); + +extern int dmabuf_sync_lock(struct dmabuf_sync *sync); + +extern int dmabuf_sync_unlock(struct dmabuf_sync *sync); + +int dmabuf_sync_single_lock(struct dma_buf *dmabuf, unsigned int type, + bool wait); + +void dmabuf_sync_single_unlock(struct dma_buf *dmabuf); + +extern int dmabuf_sync_get(struct dmabuf_sync *sync, void *sync_buf, + unsigned int type); + +extern void dmabuf_sync_put(struct dmabuf_sync *sync, struct dma_buf *dmabuf); + +extern void dmabuf_sync_put_all(struct dmabuf_sync *sync); + +#else + +static inline void dmabuf_sync_reservation_init(struct dma_buf *dmabuf) { } + +static inline void dmabuf_sync_reservation_fini(struct dma_buf *dmabuf) { } + +static inline bool is_dmabuf_sync_supported(void) { return false; } + +static inline struct dmabuf_sync *dmabuf_sync_init(void *priv, + const char *names) +{ + return ERR_PTR(0); +} + +static inline void dmabuf_sync_fini(struct dmabuf_sync *sync) { } + +static inline int dmabuf_sync_lock(struct dmabuf_sync *sync) +{ + return 0; +} + +static inline int dmabuf_sync_unlock(struct dmabuf_sync *sync) +{ + return 0; +} + +static inline int dmabuf_sync_single_lock(struct dma_buf *dmabuf, + unsigned int type, + bool wait) +{ + return 0; +} + +static inline void dmabuf_sync_single_unlock(struct dma_buf *dmabuf) +{ + return; +} + +static inline int dmabuf_sync_get(struct dmabuf_sync *sync, + void *sync_buf, + unsigned int type) +{ + return 0; +} + +static inline void dmabuf_sync_put(struct dmabuf_sync *sync, + struct dma_buf *dmabuf) { } + +static inline void dmabuf_sync_put_all(struct dmabuf_sync *sync) { } + +#endif |