Commit ae4e46b1 authored Aug 15, 2016 by Chris Wilson Committed by Sumit Semwal Aug 16, 2016

dma-buf: Wait on the reservation object when sync'ing before CPU access



Rendering operations to the dma-buf are tracked implicitly via the
reservation_object (dmabuf->resv). This is used to allow poll() to
wait upon outstanding rendering (or just query the current status of
rendering). The dma-buf sync ioctl allows userspace to prepare the
dma-buf for CPU access, which should include waiting upon rendering.
(Some drivers may need to do more work to ensure that the dma-buf mmap
is coherent as well as complete.)

v2: Always wait upon the reservation object implicitly. We choose to do
it after the native handler in case it can do so more efficiently.

Testcase: igt/prime_vgem
Testcase: igt/gem_concurrent_blit # *vgem*
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Eric Anholt <eric@anholt.net>
Cc: linux-media@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1471275738-31994-1-git-send-email-chris@chris-wilson.co.uk

parent 90844f00

drivers/dma-buf/dma-buf.c

+23 −0

Original line number	Diff line number	Diff line
		@@ -586,6 +586,22 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
		}
		EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);

		static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
		enum dma_data_direction direction)
		{
		bool write = (direction == DMA_BIDIRECTIONAL \|\|
		direction == DMA_TO_DEVICE);
		struct reservation_object *resv = dmabuf->resv;
		long ret;

		/* Wait on any implicit rendering fences */
		ret = reservation_object_wait_timeout_rcu(resv, write, true,
		MAX_SCHEDULE_TIMEOUT);
		if (ret < 0)
		return ret;

		return 0;
		}

		/**
		* dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
		@@ -608,6 +624,13 @@ int dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
		if (dmabuf->ops->begin_cpu_access)
		ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);

		/* Ensure that all fences are waited upon - but we first allow
		* the native handler the chance to do so more efficiently if it
		* chooses. A double invocation here will be reasonably cheap no-op.
		*/
		if (ret == 0)
		ret = __dma_buf_begin_cpu_access(dmabuf, direction);

		return ret;
		}
		EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access);

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