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1626f53717
Re-introduce a line-by-line composition algorithm for each pixel format. This allows more performance by not requiring an indirection per pixel read. This patch is focused on readability of the code. Line-by-line composition was introduced by [1] but rewritten back to pixel-by-pixel algorithm in [2]. At this time, nobody noticed the impact on performance, and it was merged. This patch is almost a revert of [2], but in addition efforts have been made to increase readability and maintainability of the rotation handling. The blend function is now divided in two parts: - Transformation of coordinates from the output referential to the source referential - Line conversion and blending Most of the complexity of the rotation management is avoided by using drm_rect_* helpers. The remaining complexity is around the clipping, to avoid reading/writing outside source/destination buffers. The pixel conversion is now done line-by-line, so the read_pixel_t was replaced with read_pixel_line_t callback. This way the indirection is only required once per line and per plane, instead of once per pixel and per plane. The read_line_t callbacks are very similar for most pixel format, but it is required to avoid performance impact. Some helpers for color conversion were introduced to avoid code repetition: - *_to_argb_u16: perform colors conversion. They should be inlined by the compiler, and they are used to avoid repetition between multiple variants of the same format (argb/xrgb and maybe in the future for formats like bgr formats). This new algorithm was tested with: - kms_plane (for color conversions) - kms_rotation_crc (for rotations of planes) - kms_cursor_crc (for translations of planes) - kms_rotation (for all rotations and formats combinations) [3] The performance gain was mesured with kms_fb_stress [4] with some modification to fix the writeback format. The performance improvement is around 5 to 10%. [1]: commit8ba1648567("drm: vkms: Refactor the plane composer to accept new formats") https://lore.kernel.org/all/20220905190811.25024-7-igormtorrente@gmail.com/ [2]: commit322d716a3e("drm/vkms: isolate pixel conversion functionality") https://lore.kernel.org/all/20230418130525.128733-2-mcanal@igalia.com/ [3]: https://lore.kernel.org/igt-dev/20240313-new_rotation-v2-0-6230fd5cae59@bootlin.com/ [4]: https://lore.kernel.org/all/20240422-kms_fb_stress-dev-v5-0-0c577163dc88@riseup.net/ Reviewed-by: José Expósito <jose.exposito89@gmail.com> Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com> Link: https://patchwork.freedesktop.org/patch/msgid/20241118-yuv-v14-8-2dbc2f1e222c@bootlin.com Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
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.