diff options
| -rw-r--r-- | Documentation/DocBook/device-drivers.tmpl | 36 | ||||
| -rw-r--r-- | drivers/dma-buf/dma-buf.c | 7 | ||||
| -rw-r--r-- | drivers/dma-buf/reservation.c | 72 | ||||
| -rw-r--r-- | include/linux/dma-buf.h | 13 | ||||
| -rw-r--r-- | include/linux/fence.h | 2 | ||||
| -rw-r--r-- | include/linux/reservation.h | 53 |
6 files changed, 169 insertions, 14 deletions
diff --git a/Documentation/DocBook/device-drivers.tmpl b/Documentation/DocBook/device-drivers.tmpl index de79efdad46c..8c68768ebee5 100644 --- a/Documentation/DocBook/device-drivers.tmpl +++ b/Documentation/DocBook/device-drivers.tmpl @@ -128,16 +128,44 @@ X!Edrivers/base/interface.c !Edrivers/base/platform.c !Edrivers/base/bus.c </sect1> - <sect1><title>Device Drivers DMA Management</title> + <sect1> + <title>Buffer Sharing and Synchronization</title> + <para> + The dma-buf subsystem provides the framework for sharing buffers + for hardware (DMA) access across multiple device drivers and + subsystems, and for synchronizing asynchronous hardware access. + </para> + <para> + This is used, for example, by drm "prime" multi-GPU support, but + is of course not limited to GPU use cases. + </para> + <para> + The three main components of this are: (1) dma-buf, representing + a sg_table and exposed to userspace as a file descriptor to allow + passing between devices, (2) fence, which provides a mechanism + to signal when one device as finished access, and (3) reservation, + which manages the shared or exclusive fence(s) associated with + the buffer. + </para> + <sect2><title>dma-buf</title> !Edrivers/dma-buf/dma-buf.c +!Iinclude/linux/dma-buf.h + </sect2> + <sect2><title>reservation</title> +!Pdrivers/dma-buf/reservation.c Reservation Object Overview +!Edrivers/dma-buf/reservation.c +!Iinclude/linux/reservation.h + </sect2> + <sect2><title>fence</title> !Edrivers/dma-buf/fence.c -!Edrivers/dma-buf/seqno-fence.c !Iinclude/linux/fence.h +!Edrivers/dma-buf/seqno-fence.c !Iinclude/linux/seqno-fence.h -!Edrivers/dma-buf/reservation.c -!Iinclude/linux/reservation.h !Edrivers/dma-buf/sync_file.c !Iinclude/linux/sync_file.h + </sect2> + </sect1> + <sect1><title>Device Drivers DMA Management</title> !Edrivers/base/dma-coherent.c !Edrivers/base/dma-mapping.c </sect1> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 4a2c07ee6677..6355ab38d630 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -33,6 +33,7 @@ #include <linux/seq_file.h> #include <linux/poll.h> #include <linux/reservation.h> +#include <linux/mm.h> #include <uapi/linux/dma-buf.h> @@ -90,7 +91,7 @@ static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma) dmabuf = file->private_data; /* check for overflowing the buffer's size */ - if (vma->vm_pgoff + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) > + if (vma->vm_pgoff + vma_pages(vma) > dmabuf->size >> PAGE_SHIFT) return -EINVAL; @@ -723,11 +724,11 @@ int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma, return -EINVAL; /* check for offset overflow */ - if (pgoff + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) < pgoff) + if (pgoff + vma_pages(vma) < pgoff) return -EOVERFLOW; /* check for overflowing the buffer's size */ - if (pgoff + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) > + if (pgoff + vma_pages(vma) > dmabuf->size >> PAGE_SHIFT) return -EINVAL; diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c index c0bd5722c997..9566a62ad8e3 100644 --- a/drivers/dma-buf/reservation.c +++ b/drivers/dma-buf/reservation.c @@ -35,6 +35,17 @@ #include <linux/reservation.h> #include <linux/export.h> +/** + * DOC: Reservation Object Overview + * + * The reservation object provides a mechanism to manage shared and + * exclusive fences associated with a buffer. A reservation object + * can have attached one exclusive fence (normally associated with + * write operations) or N shared fences (read operations). The RCU + * mechanism is used to protect read access to fences from locked + * write-side updates. + */ + DEFINE_WW_CLASS(reservation_ww_class); EXPORT_SYMBOL(reservation_ww_class); @@ -43,9 +54,17 @@ EXPORT_SYMBOL(reservation_seqcount_class); const char reservation_seqcount_string[] = "reservation_seqcount"; EXPORT_SYMBOL(reservation_seqcount_string); -/* - * Reserve space to add a shared fence to a reservation_object, - * must be called with obj->lock held. + +/** + * reservation_object_reserve_shared - Reserve space to add a shared + * fence to a reservation_object. + * @obj: reservation object + * + * Should be called before reservation_object_add_shared_fence(). Must + * be called with obj->lock held. + * + * RETURNS + * Zero for success, or -errno */ int reservation_object_reserve_shared(struct reservation_object *obj) { @@ -180,7 +199,11 @@ done: fence_put(old_fence); } -/* +/** + * reservation_object_add_shared_fence - Add a fence to a shared slot + * @obj: the reservation object + * @fence: the shared fence to add + * * Add a fence to a shared slot, obj->lock must be held, and * reservation_object_reserve_shared_fence has been called. */ @@ -200,6 +223,13 @@ void reservation_object_add_shared_fence(struct reservation_object *obj, } EXPORT_SYMBOL(reservation_object_add_shared_fence); +/** + * reservation_object_add_excl_fence - Add an exclusive fence. + * @obj: the reservation object + * @fence: the shared fence to add + * + * Add a fence to the exclusive slot. The obj->lock must be held. + */ void reservation_object_add_excl_fence(struct reservation_object *obj, struct fence *fence) { @@ -233,6 +263,18 @@ void reservation_object_add_excl_fence(struct reservation_object *obj, } EXPORT_SYMBOL(reservation_object_add_excl_fence); +/** + * reservation_object_get_fences_rcu - Get an object's shared and exclusive + * fences without update side lock held + * @obj: the reservation object + * @pfence_excl: the returned exclusive fence (or NULL) + * @pshared_count: the number of shared fences returned + * @pshared: the array of shared fence ptrs returned (array is krealloc'd to + * the required size, and must be freed by caller) + * + * RETURNS + * Zero or -errno + */ int reservation_object_get_fences_rcu(struct reservation_object *obj, struct fence **pfence_excl, unsigned *pshared_count, @@ -319,6 +361,18 @@ unlock: } EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu); +/** + * reservation_object_wait_timeout_rcu - Wait on reservation's objects + * shared and/or exclusive fences. + * @obj: the reservation object + * @wait_all: if true, wait on all fences, else wait on just exclusive fence + * @intr: if true, do interruptible wait + * @timeout: timeout value in jiffies or zero to return immediately + * + * RETURNS + * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or + * greater than zer on success. + */ long reservation_object_wait_timeout_rcu(struct reservation_object *obj, bool wait_all, bool intr, unsigned long timeout) @@ -416,6 +470,16 @@ reservation_object_test_signaled_single(struct fence *passed_fence) return ret; } +/** + * reservation_object_test_signaled_rcu - Test if a reservation object's + * fences have been signaled. + * @obj: the reservation object + * @test_all: if true, test all fences, otherwise only test the exclusive + * fence + * + * RETURNS + * true if all fences signaled, else false + */ bool reservation_object_test_signaled_rcu(struct reservation_object *obj, bool test_all) { diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 3fe90d494edb..4551c6f2a6c4 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -112,19 +112,24 @@ struct dma_buf_ops { * @file: file pointer used for sharing buffers across, and for refcounting. * @attachments: list of dma_buf_attachment that denotes all devices attached. * @ops: dma_buf_ops associated with this buffer object. + * @lock: used internally to serialize list manipulation, attach/detach and vmap/unmap + * @vmapping_counter: used internally to refcnt the vmaps + * @vmap_ptr: the current vmap ptr if vmapping_counter > 0 * @exp_name: name of the exporter; useful for debugging. * @owner: pointer to exporter module; used for refcounting when exporter is a * kernel module. * @list_node: node for dma_buf accounting and debugging. * @priv: exporter specific private data for this buffer object. * @resv: reservation object linked to this dma-buf + * @poll: for userspace poll support + * @cb_excl: for userspace poll support + * @cb_shared: for userspace poll support */ struct dma_buf { size_t size; struct file *file; struct list_head attachments; const struct dma_buf_ops *ops; - /* mutex to serialize list manipulation, attach/detach and vmap/unmap */ struct mutex lock; unsigned vmapping_counter; void *vmap_ptr; @@ -188,9 +193,11 @@ struct dma_buf_export_info { /** * helper macro for exporters; zeros and fills in most common values + * + * @name: export-info name */ -#define DEFINE_DMA_BUF_EXPORT_INFO(a) \ - struct dma_buf_export_info a = { .exp_name = KBUILD_MODNAME, \ +#define DEFINE_DMA_BUF_EXPORT_INFO(name) \ + struct dma_buf_export_info name = { .exp_name = KBUILD_MODNAME, \ .owner = THIS_MODULE } /** diff --git a/include/linux/fence.h b/include/linux/fence.h index 2b17698b60b8..2056e9fd0138 100644 --- a/include/linux/fence.h +++ b/include/linux/fence.h @@ -49,6 +49,8 @@ struct fence_cb; * @timestamp: Timestamp when the fence was signaled. * @status: Optional, only valid if < 0, must be set before calling * fence_signal, indicates that the fence has completed with an error. + * @child_list: list of children fences + * @active_list: list of active fences * * the flags member must be manipulated and read using the appropriate * atomic ops (bit_*), so taking the spinlock will not be needed most diff --git a/include/linux/reservation.h b/include/linux/reservation.h index 49d057655d62..b0f305e77b7f 100644 --- a/include/linux/reservation.h +++ b/include/linux/reservation.h @@ -49,12 +49,27 @@ extern struct ww_class reservation_ww_class; extern struct lock_class_key reservation_seqcount_class; extern const char reservation_seqcount_string[]; +/** + * struct reservation_object_list - a list of shared fences + * @rcu: for internal use + * @shared_count: table of shared fences + * @shared_max: for growing shared fence table + * @shared: shared fence table + */ struct reservation_object_list { struct rcu_head rcu; u32 shared_count, shared_max; struct fence __rcu *shared[]; }; +/** + * struct reservation_object - a reservation object manages fences for a buffer + * @lock: update side lock + * @seq: sequence count for managing RCU read-side synchronization + * @fence_excl: the exclusive fence, if there is one currently + * @fence: list of current shared fences + * @staged: staged copy of shared fences for RCU updates + */ struct reservation_object { struct ww_mutex lock; seqcount_t seq; @@ -68,6 +83,10 @@ struct reservation_object { #define reservation_object_assert_held(obj) \ lockdep_assert_held(&(obj)->lock.base) +/** + * reservation_object_init - initialize a reservation object + * @obj: the reservation object + */ static inline void reservation_object_init(struct reservation_object *obj) { @@ -79,6 +98,10 @@ reservation_object_init(struct reservation_object *obj) obj->staged = NULL; } +/** + * reservation_object_fini - destroys a reservation object + * @obj: the reservation object + */ static inline void reservation_object_fini(struct reservation_object *obj) { @@ -106,6 +129,14 @@ reservation_object_fini(struct reservation_object *obj) ww_mutex_destroy(&obj->lock); } +/** + * reservation_object_get_list - get the reservation object's + * shared fence list, with update-side lock held + * @obj: the reservation object + * + * Returns the shared fence list. Does NOT take references to + * the fence. The obj->lock must be held. + */ static inline struct reservation_object_list * reservation_object_get_list(struct reservation_object *obj) { @@ -113,6 +144,17 @@ reservation_object_get_list(struct reservation_object *obj) reservation_object_held(obj)); } +/** + * reservation_object_get_excl - get the reservation object's + * exclusive fence, with update-side lock held + * @obj: the reservation object + * + * Returns the exclusive fence (if any). Does NOT take a + * reference. The obj->lock must be held. + * + * RETURNS + * The exclusive fence or NULL + */ static inline struct fence * reservation_object_get_excl(struct reservation_object *obj) { @@ -120,6 +162,17 @@ reservation_object_get_excl(struct reservation_object *obj) reservation_object_held(obj)); } +/** + * reservation_object_get_excl_rcu - get the reservation object's + * exclusive fence, without lock held. + * @obj: the reservation object + * + * If there is an exclusive fence, this atomically increments it's + * reference count and returns it. + * + * RETURNS + * The exclusive fence or NULL if none + */ static inline struct fence * reservation_object_get_excl_rcu(struct reservation_object *obj) { |