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With bigjoiner the master crtc is the one that will send out the uapi event/etc. We want that to happen after all the slaves are done, so let's try to do the commits in reverse order so that the master comes last. Even worse, the modeset helper will simply complete the commit on the slave pipe immediately as it consider the crtc to be inactive (it can't see our crtc_state->hw.active/etc.). With regular sync updates this generally doesn't matter all that much as the slave pipe should typically finish its work during the same frame as the master pipe. However in case the slave pipe's commit slips into the next frame we end up in a bit of trouble. This is most visible with either async flips (currently disabled with bigjoiner exactly for this reason), and DSB gamma updates. With DSB the problem happens because the DSB itself will wait until the next start vblank before starting to execute. So if the master pipe already finished its commit and the DSB on the slave pipe is still waiting for the next vblank we will assume the DSB as gotten stuck and terminate it. Reversing the commit order should ameliarate this for the most part as the master pipe is guaranteed to start its commit after the slave pipe started. The one thing that can still screw us over is the fact that we aren't necessarily going to commit the pipes in the reverse order as the actual order is dictated by the DDB overlap avoidance. But that can only happen while other pipes are being enabled/disabled, and so in the normal steady state we should be safe. The full fix will involve making the commit machinery aware of the slave pipes and not finish their commits prematurely. But that will involve a bit more work than this. And this commit order reversal will still be beneficial to avoid userspace getting an -EBUSY from the following page flip if the second pipe's commit does stretch into the next frame. Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20240404213441.17637-2-ville.syrjala@linux.intel.com Reviewed-by: Arun R Murthy <arun.r.murthy@intel.com> Reviewed-by: Vandita Kulkarni <vandita.kulkarni@intel.com> |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| 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 reStructuredText 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.