drm/ttm: add a way to bo_wait for either the last read or last write
Sometimes we want to know whether a buffer is busy and wait for it (bo_wait).
However, sometimes it would be more useful to be able to query whether
a buffer is busy and being either read or written, and wait until it's stopped
being either read or written. The point of this is to be able to avoid
unnecessary waiting, e.g. if a GPU has written something to a buffer and is now
reading that buffer, and a CPU wants to map that buffer for read, it needs to
only wait for the last write. If there were no write, there wouldn't be any
waiting needed.
This, or course, requires user space drivers to send read/write flags
with each relocation (like we have read/write domains in radeon, so we can
actually use those for something useful now).
Now how this patch works:
The read/write flags should passed to ttm_validate_buffer. TTM maintains
separate sync objects of the last read and write for each buffer, in addition
to the sync object of the last use of a buffer. ttm_bo_wait then operates
with one the sync objects.
Signed-off-by: Marek Olšák <maraeo@gmail.com>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index 42e3469..da957bf 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -44,6 +44,11 @@
struct drm_mm_node;
+enum ttm_buffer_usage {
+ TTM_USAGE_READ = 1,
+ TTM_USAGE_WRITE = 2,
+ TTM_USAGE_READWRITE = TTM_USAGE_READ | TTM_USAGE_WRITE
+};
/**
* struct ttm_placement
@@ -174,7 +179,10 @@
* the bo_device::lru_lock.
* @reserved: Deadlock-free lock used for synchronization state transitions.
* @sync_obj_arg: Opaque argument to synchronization object function.
- * @sync_obj: Pointer to a synchronization object.
+ * @sync_obj: Pointer to a synchronization object of a last read or write,
+ * whichever is later.
+ * @sync_obj_read: Pointer to a synchronization object of a last read.
+ * @sync_obj_write: Pointer to a synchronization object of a last write.
* @priv_flags: Flags describing buffer object internal state.
* @vm_rb: Rb node for the vm rb tree.
* @vm_node: Address space manager node.
@@ -258,6 +266,8 @@
void *sync_obj_arg;
void *sync_obj;
+ void *sync_obj_read;
+ void *sync_obj_write;
unsigned long priv_flags;
/**
@@ -325,6 +335,7 @@
* @bo: The buffer object.
* @interruptible: Use interruptible wait.
* @no_wait: Return immediately if buffer is busy.
+ * @usage: Whether to wait for the last read and/or the last write.
*
* This function must be called with the bo::mutex held, and makes
* sure any previous rendering to the buffer is completed.
@@ -334,7 +345,8 @@
* Returns -ERESTARTSYS if interrupted by a signal.
*/
extern int ttm_bo_wait(struct ttm_buffer_object *bo, bool lazy,
- bool interruptible, bool no_wait);
+ bool interruptible, bool no_wait,
+ enum ttm_buffer_usage usage);
/**
* ttm_bo_validate
*