From: Gustavo Padovan gustavo.padovan@collabora.co.uk
Document IN_FENCE_FD and OUT_FENCE_PTR properties.
Signed-off-by: Gustavo Padovan gustavo.padovan@collabora.co.uk --- Documentation/gpu/drm-kms.rst | 6 ++++++ drivers/gpu/drm/drm_atomic.c | 31 +++++++++++++++++++++++++++++++ 2 files changed, 37 insertions(+)
diff --git a/Documentation/gpu/drm-kms.rst b/Documentation/gpu/drm-kms.rst index 568f3c2..cdc9539 100644 --- a/Documentation/gpu/drm-kms.rst +++ b/Documentation/gpu/drm-kms.rst @@ -287,6 +287,12 @@ Tile Group Property .. kernel-doc:: drivers/gpu/drm/drm_connector.c :doc: Tile group
+Explicit Fencing Properties +--------------------------- + +.. kernel-doc:: drivers/gpu/drm/drm_atomic.c + :doc: explicit fencing properties + Existing KMS Properties -----------------------
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c index b476ec5..7f33031 100644 --- a/drivers/gpu/drm/drm_atomic.c +++ b/drivers/gpu/drm/drm_atomic.c @@ -1809,6 +1809,37 @@ void drm_atomic_clean_old_fb(struct drm_device *dev, } EXPORT_SYMBOL(drm_atomic_clean_old_fb);
+/** + * DOC: explicit fencing properties + * + * Explicit fencing allows userspace to control the buffer synchronization + * between devices. A Fence or a group of fences are trasnfered to/from + * userspace using Sync File fds and there are two DRM properties for that. + * IN_FENCE_FD on each DRM Plane to send fences to the kernel and + * OUT_FENCE_PTR on each DRM CRTC to receive fences from the kernel. + * + * "IN_FENCE_FD”: + * Use this property to pass a fence that DRM should wait on before + * proceeding with the Atomic Commit request and show the framebuffer for + * the plane on the screen. The fence can be either a normal fence or a + * merged one, the sync_file framework will handle both case and use a + * fence_array if a merged fence is received. Passing -1 here means no + * fences to wait on. + * + * "OUT_FENCE_PTR”: + * Use this property to pass a file descriptor pointer to DRM. Once the + * Atomic Commit request call returns OUT_FENCE_PTR will be filled with + * the file descriptor number of a Sync File. This Sync File contains the + * CRTC fence that will be signaled when all framebuffers present on the + * Atomic Commit * request for that given CRTC are scanned out on the + * screen. + * + * The Atomic Commit request fails if a invalid pointer is passed. If the + * Atomic Commit request fails for any other reason the out fence fd + * returned will be -1. On a Atomic Commit with the + * DRM_MODE_ATOMIC_TEST_ONLY flag the out fence will also be set to -1. + */ + static struct dma_fence *get_crtc_fence(struct drm_crtc *crtc) { struct dma_fence *fence;
On Mon, Nov 21, 2016 at 12:48:13PM +0900, Gustavo Padovan wrote:
From: Gustavo Padovan gustavo.padovan@collabora.co.uk
Document IN_FENCE_FD and OUT_FENCE_PTR properties.
Signed-off-by: Gustavo Padovan gustavo.padovan@collabora.co.uk
Documentation/gpu/drm-kms.rst | 6 ++++++ drivers/gpu/drm/drm_atomic.c | 31 +++++++++++++++++++++++++++++++ 2 files changed, 37 insertions(+)
diff --git a/Documentation/gpu/drm-kms.rst b/Documentation/gpu/drm-kms.rst index 568f3c2..cdc9539 100644 --- a/Documentation/gpu/drm-kms.rst +++ b/Documentation/gpu/drm-kms.rst @@ -287,6 +287,12 @@ Tile Group Property .. kernel-doc:: drivers/gpu/drm/drm_connector.c :doc: Tile group
+Explicit Fencing Properties +---------------------------
+.. kernel-doc:: drivers/gpu/drm/drm_atomic.c
- :doc: explicit fencing properties
Existing KMS Properties
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c index b476ec5..7f33031 100644 --- a/drivers/gpu/drm/drm_atomic.c +++ b/drivers/gpu/drm/drm_atomic.c @@ -1809,6 +1809,37 @@ void drm_atomic_clean_old_fb(struct drm_device *dev, } EXPORT_SYMBOL(drm_atomic_clean_old_fb);
+/**
- DOC: explicit fencing properties
- Explicit fencing allows userspace to control the buffer synchronization
- between devices. A Fence or a group of fences are trasnfered to/from
s/trasn/trans/
- userspace using Sync File fds and there are two DRM properties for that.
- IN_FENCE_FD on each DRM Plane to send fences to the kernel and
- OUT_FENCE_PTR on each DRM CRTC to receive fences from the kernel.
I think a bit about implicit vs. explicit fencing would be useful in a separate paragraph:
"As a contrast, with implicit fencing the kernel keeps track of any ongoing rendering, and automatically ensures that the atomic update waits for any pending rendering to complete. For shared buffers represented with a struct &dma_buf this is tracked in &reservation_object structures. Implicit syncing is how Linux traditionally worked (e.g. DRI2/3 on X.org), whereas explicit fencing is what Android wants."
- "IN_FENCE_FD”:
- Use this property to pass a fence that DRM should wait on before
- proceeding with the Atomic Commit request and show the framebuffer for
- the plane on the screen. The fence can be either a normal fence or a
- merged one, the sync_file framework will handle both case and use a
s/case/cases/
- fence_array if a merged fence is received. Passing -1 here means no
- fences to wait on.
Please also document what the expecation is for a TEST_ONLY commit.
I think a line or so about the driver interface would be good here, e.g.
"On the driver side the fence is stored @fence parameter of struct &drm_plane_state. Drivers which also support implicit fencing should set the implicit fence using drm_atomic_set_fence_for_plane(), to make sure there's consistent behaviour between drivers in precedence of implicit vs. explicit fencing."
- "OUT_FENCE_PTR”:
- Use this property to pass a file descriptor pointer to DRM. Once the
- Atomic Commit request call returns OUT_FENCE_PTR will be filled with
- the file descriptor number of a Sync File. This Sync File contains the
- CRTC fence that will be signaled when all framebuffers present on the
- Atomic Commit * request for that given CRTC are scanned out on the
- screen.
- The Atomic Commit request fails if a invalid pointer is passed. If the
- Atomic Commit request fails for any other reason the out fence fd
- returned will be -1. On a Atomic Commit with the
- DRM_MODE_ATOMIC_TEST_ONLY flag the out fence will also be set to -1.
Same here about driver interface:
"Note that out-fences don't have a special interface to drivers and are internally represented by a struct &drm_pending_vblank_event in struct &drm_crtc_state, which is also used by the async atomic commit helpers and for the DRM event handling for existing userspace."
Cheers, Daniel
- */
static struct dma_fence *get_crtc_fence(struct drm_crtc *crtc) { struct dma_fence *fence; -- 2.5.5
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-
Daniel Vetter -
Gustavo Padovan