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When doing an asynchronous page flip (PAGE_FLIP ioctl with the DRM_MODE_PAGE_FLIP_ASYNC flag set), the current code waits for the possible GPU buffer being rendered through a call to vc4_queue_seqno_cb(). On the BCM2835-37, the GPU driver is part of the vc4 driver and that function is defined in vc4_gem.c to wait for the buffer to be rendered, and once it's done, call a callback. However, on the BCM2711 used on the RaspberryPi4, the GPU driver is separate (v3d) and that function won't do anything. This was working because we were going into a path, due to uninitialized variables, that was always scheduling the callback. However, we were never actually waiting for the buffer to be rendered which was resulting in frames being displayed out of order. The generic API to signal those kind of completion in the kernel are the DMA fences, and fortunately the v3d drivers supports them and signal when its job is done. That API also provides an equivalent function that allows to have a callback being executed when the fence is signalled as done. Let's change our driver a bit to rely on the previous function for the older SoCs, and on DMA fences for the BCM2711. Signed-off-by: Maxime Ripard <maxime@cerno.tech> Reviewed-by: Melissa Wen <mwen@igalia.com> Link: https://lore.kernel.org/r/20220610115149.964394-14-maxime@cerno.tech |
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| 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 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.