76818cdd11
According to the KMS man page, there is a "Coverage" alpha blend mode that assumes the pixel color values have NOT been pre-multiplied and will be done when the actual blending to the background color values happens. Previously, this mode hasn't been enabled in our driver and it was assumed that all normal overlay planes are pre-multiplied by default. When a 3rd party app is used to input a image in a specific format, e.g. PNG, as a source of a overlay plane to blend with the background primary plane, the pixel color values are not pre-multiplied. So by adding "Coverage" blend mode, our driver will support those cases. Issue fixed: Overlay plane alpha channel blending is incorrect Issue tracker: https://gitlab.freedesktop.org/drm/amd/-/issues/1769 Reference: https://dri.freedesktop.org/docs/drm/gpu/drm-kms.html#plane-composition-properties Adding Coverage support also enables IGT kms_plane_alpha_blend Coverage subtests: 1. coverage-7efc 2. coverage-vs-premult-vs-constant Changes 1. Add DRM_MODE_BLEND_COVERAGE blend mode capability 2. Add "pre_multiplied_alpha" flag for Coverage case 3. Read the correct flag and set the DCN MPCC pre_multiplied register bit (only on overlay plane) Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1769 Signed-off-by: Sung Joon Kim <Sungjoon.Kim@amd.com> Reviewed-by: Melissa Wen <mwen@igalia.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.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 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.