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We want vblank counts and timestamps of flip completion as sent in pageflip completion events to be consistent with the vblank count and timestamp of the vblank of flip completion, like in non VRR mode. In VRR mode, drm_update_vblank_count() - and thereby vblank count and timestamp updates - must be delayed until after the end of front-porch of each vblank, as it is only safe to calculate vblank timestamps outside of the front-porch, when we actually know when the vblank will end or has ended. The function drm_update_vblank_count() which updates timestamps and counts gets called by drm_crtc_accurate_vblank_count() or by drm_crtc_handle_vblank(). Therefore we must make sure that pageflip events for a completed flip are only sent out after drm_crtc_accurate_vblank_count() or drm_crtc_handle_vblank() is executed, after end of front-porch for the vblank of flip completion. Two cases: a) Pageflip irq handler executes inside front-porch: In this case we must defer sending pageflip events until drm_crtc_handle_vblank() executes after end of front-porch, and thereby calculates proper vblank count and timestamp. Iow. the pflip irq handler must just arm a pageflip event to be sent out by drm_crtc_handle_vblank() later on. b) Pageflip irq handler executes after end of front-porch, e.g., after flip completion in back-porch or due to a massively delayed handler invocation into the active scanout of the new frame. In this case we can call drm_crtc_accurate_vblank_count() to safely force calculation of a proper vblank count and timestamp, and must send the pageflip completion event ourselves from the pageflip irq handler. This is the same behaviour as needed for standard fixed refresh rate mode. To decide from within pageflip handler if we are in case a) or b), we check the current scanout position against the boundary of front-porch. In non-VRR mode we just do what we did in the past. Signed-off-by: Mario Kleiner <mario.kleiner.de@gmail.com> Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> |
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| Documentation | ||
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| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
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| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
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| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.