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This adds the common plumbing and support for the VK_GOOGLE_display_timing
extension. A followup commit will enable it for KHR_display. It should
also optionally work for suitable other backends like Wayland and X11
on suitable Wayland and X11 servers, if those servers and backends
mostly support VK_EXT_present_timing (minus the relative timing support,
which is not needed for this extension to work). However, fully conformant
use on Wayland or X11 is not possible, as the extension lacks the ability
to report per VKSurface capabilities wrt. timing. Therefore the extension
should only be enabled for Wayland or X11 via explicit opt-in, not by
default.
The extension provides two things:
1) Detailed information about when frames are displayed, including
slack time between GPU execution and display frame.
2) Absolute time control over swapchain queue processing. This allows
the application to request frames be displayed at specific
absolute times, using the same timebase as that used in 1).
It is implemented on top of the VK_EXT_present_timing extension
infrastructure.
This code is inspired by Emma Anholt's work from late 2025, which itself
is based on Keith Packard's original work from 2018. Only a few lines of
their code is left though after an almost complete rewrite on top of
EXT_present_timing. Specifically calculation of .earliestPresentTime
and .presentMargin in fixed refresh rate (FRR) mode is based on Keith
original math, and the followup commit for driver enable is a modified
version of Emma's commit.
See MR 38472 for reference of Emma's work, based on Keith's work.
The final implementation as a whole is so far successfully tested on top
of an AMD Polaris gpu (radv), a Intel Kabylake gpu (anv), and Mesa CI
for direct display mode on AMD radv, Intel anv, and Qualcomm Adreno turnip.
Both VK_EXT_present_timing and VK_GOOGLE_display_timing can be enabled
at the same time on a VkDevice, but only one of the extensions can be
used on a given swapchain for that device. If both extensions are enabled
on a device and VK_EXT_present_timing is requested on some swapchains, it
will be used on those swapchains, whereas on all other swapchains the
VK_GOOGLE_display_timing will be used.
On drivers which don't support queue timestamps, reported values for
earliestPresentTime are identical to actualPresentTime, and presentMargin
is reported as zero, which is a reasonable fallback behaviour. Currently
drivers with this limitation would be pvr, panvk and kk.
Signed-off-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Reviewed-by: Hans-Kristian Arntzen <post@arntzen-software.no>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/41168>
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| VERSION | ||
`Mesa <https://mesa3d.org>`_ - The 3D Graphics Library ====================================================== Source ------ This repository lives at https://gitlab.freedesktop.org/mesa/mesa. Other repositories are likely forks, and code found there is not supported. Build & install --------------- You can find more information in our documentation (`docs/install.rst <https://docs.mesa3d.org/install.html>`_), but the recommended way is to use Meson (`docs/meson.rst <https://docs.mesa3d.org/meson.html>`_): .. code-block:: sh $ meson setup build $ ninja -C build/ $ sudo ninja -C build/ install Support ------- Many Mesa devs hang on IRC; if you're not sure which channel is appropriate, you should ask your question on `OFTC's #dri-devel <irc://irc.oftc.net/dri-devel>`_, someone will redirect you if necessary. Remember that not everyone is in the same timezone as you, so it might take a while before someone qualified sees your question. To figure out who you're talking to, or which nick to ping for your question, check out `Who's Who on IRC <https://dri.freedesktop.org/wiki/WhosWho/>`_. The next best option is to ask your question in an email to the mailing lists: `mesa-dev\@lists.freedesktop.org <https://lists.freedesktop.org/mailman/listinfo/mesa-dev>`_ Bug reports ----------- If you think something isn't working properly, please file a bug report (`docs/bugs.rst <https://docs.mesa3d.org/bugs.html>`_). Contributing ------------ Contributions are welcome, and step-by-step instructions can be found in our documentation (`docs/submittingpatches.rst <https://docs.mesa3d.org/submittingpatches.html>`_). Note that Mesa uses gitlab for patches submission, review and discussions.