98 lines
3.4 KiB
Diff
98 lines
3.4 KiB
Diff
From a0bc59127231cbea506651c362d4836a0ff5591f Mon Sep 17 00:00:00 2001
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From: Maxime Ripard <maxime@cerno.tech>
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Date: Wed, 8 Sep 2021 21:12:26 +0200
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Subject: [PATCH] drm/vc4: Fix out of order frames during asynchronous
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page flips
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When doing an asynchronous page flip (PAGE_FLIP ioctl with the
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DRM_MODE_PAGE_FLIP_ASYNC flag set), the current code waits for the
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possible GPU buffer being rendered through a call to
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vc4_queue_seqno_cb().
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On the BCM2835-37, the GPU driver is part of the vc4 driver and that
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function is defined in vc4_gem.c to wait for the buffer to be rendered,
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and once it's done, call a callback.
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However, on the BCM2711 used on the RaspberryPi4, the GPU driver is
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separate (v3d) and that function won't do anything. This was working
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because we were going into a path, due to uninitialized variables, that
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was always scheduling the callback.
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However, we were never actually waiting for the buffer to be rendered
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which was resulting in frames being displayed out of order.
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The generic API to signal those kind of completion in the kernel are the
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DMA fences, and fortunately the v3d drivers supports them and signal
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when its job is done. That API also provides an equivalent function that
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allows to have a callback being executed when the fence is signalled as
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done.
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Let's change our driver a bit to rely on the previous function for the
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older SoCs, and on DMA fences for the BCM2711.
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Signed-off-by: Maxime Ripard <maxime@cerno.tech>
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---
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drivers/gpu/drm/vc4/vc4_crtc.c | 37 ++++++++++++++++++++++++++++++++--
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1 file changed, 35 insertions(+), 2 deletions(-)
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--- a/drivers/gpu/drm/vc4/vc4_crtc.c
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+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
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@@ -797,6 +797,7 @@ struct vc4_async_flip_state {
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struct drm_pending_vblank_event *event;
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struct vc4_seqno_cb cb;
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+ struct dma_fence_cb fence_cb;
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};
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/* Called when the V3D execution for the BO being flipped to is done, so that
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@@ -842,6 +843,39 @@ vc4_async_page_flip_complete(struct vc4_
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kfree(flip_state);
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}
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+static void vc4_async_page_flip_fence_complete(struct dma_fence *fence,
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+ struct dma_fence_cb *cb)
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+{
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+ struct vc4_async_flip_state *flip_state =
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+ container_of(cb, struct vc4_async_flip_state, fence_cb);
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+
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+ vc4_async_page_flip_complete(&flip_state->cb);
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+ dma_fence_put(fence);
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+}
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+
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+static int vc4_async_set_fence_cb(struct drm_device *dev,
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+ struct vc4_async_flip_state *flip_state)
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+{
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+ struct drm_framebuffer *fb = flip_state->fb;
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+ struct drm_gem_cma_object *cma_bo = drm_fb_cma_get_gem_obj(fb, 0);
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+ struct vc4_dev *vc4 = to_vc4_dev(dev);
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+ struct dma_fence *fence;
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+
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+ if (!vc4->hvs->hvs5) {
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+ struct vc4_bo *bo = to_vc4_bo(&cma_bo->base);
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+
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+ return vc4_queue_seqno_cb(dev, &flip_state->cb, bo->seqno,
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+ vc4_async_page_flip_complete);
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+ }
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+
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+ fence = dma_fence_get(dma_resv_excl_fence(cma_bo->base.resv));
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+ if (dma_fence_add_callback(fence, &flip_state->fence_cb,
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+ vc4_async_page_flip_fence_complete))
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+ vc4_async_page_flip_fence_complete(fence, &flip_state->fence_cb);
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+
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+ return 0;
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+}
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+
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/* Implements async (non-vblank-synced) page flips.
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*
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* The page flip ioctl needs to return immediately, so we grab the
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@@ -902,8 +936,7 @@ static int vc4_async_page_flip(struct dr
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*/
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drm_atomic_set_fb_for_plane(plane->state, fb);
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- vc4_queue_seqno_cb(dev, &flip_state->cb, bo->seqno,
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- vc4_async_page_flip_complete);
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+ vc4_async_set_fence_cb(dev, flip_state);
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/* Driver takes ownership of state on successful async commit. */
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return 0;
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