Flip pages asynchronously has been available for a long time in DRM through the old API. This operation allows userspace to update the display content as soon as possible, regardless of the vblank. However, it still not possible to do so using DRM's Atomic commit API yet. This talk will present the progress made so far to enable this, the challenges and the remaining work to get this merged. (c) X.Org Developer Conference (XDC) 2022 October 4-6, 2022 Minneapolis, Minnesota, USA https://indico.freedesktop.org/event/2/

1. Async page flip in DRM
atomic API
André Almeida @ Igalia
XDC 2022
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2. Flipping pages
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3. Flipping pages
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4. Flipping pages
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5. Flipping pages asynchronously
Cool for gaming use-cases
more fps I guess
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6. Legacy async support
drmModePageFlip(fd, crtc, fbn,
DRM_MODE_PAGE_FLIP_EVENT | DRM_MODE_PAGE_FLIP_ASYNC,
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7. Legacy async support
amdgpu
i915
nouveau
radeon
vc4
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8. Atomic support
drm_dbg_atomic(dev,
"commit failed: invalid flag DRM_MODE_PAGE_FLIP_ASYN
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9. Atomic support
How to get this into atomic?
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10. Legacy DRM (in an atomic way)
[drm:drm_ioctl] DRM_IOCTL_MODE_PAGE_FLIP
amdgpu [drm:drm_atomic_state_init] Allocated 263939d
amdgpu [drm:drm_atomic_commit] committing 263939dd
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11. Legacy DRM (in an atomic way)
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12. Wiring up things
int drm_mode_atomic_ioctl(struct drm_device *dev,
+ if (arg->flags & DRM_MODE_PAGE_FLIP_ASYNC)
+ set_async_flip(state);
feat. Simon Ser
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13. Wiring up things
+/**
+ * DRM_CAP_ATOMIC_ASYNC_PAGE_FLIP
+ *
+ * If set to 1, the driver supports &DRM_MODE_PAGE_
+ * commits.
+ */
+#define DRM_CAP_ATOMIC_ASYNC_PAGE_FLIP 0x15
feat. Simon Ser
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14. Wiring up things
DRM uAPI should reject async with other updates
Just on primary plane
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15. Degraded async
Up until now, amdgpu was silently degrading to vsync
when user-space requested an async flip but the
hardware didn't support it.
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16. What's done
IGT test
gamescope support
DRM drivers
amdgpu waiting to be merged
i915 works, I'll send a patch
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17. What's done
[PATCH v3 0/6] Add support for atomic async page-
flips
https://lore.kernel.org/dri-devel/20220929184307.2
58331-1-contact@emersion.fr/
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18. What's next?
Wayland protocol: tearing updates
Your driver?
Hint: make legacy go through atomic
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19. Lessons learned
Sometimes the work is done, it just need to connect
some wires :-)
Maybe more legacy things can be activated for
atomic
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20. Thanks!
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