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The all video ports of rk3568/rk3588 share the same OVL_LAYER_SEL
and OVL_PORT_SEL registers, and the configuration of these two registers
can be set to take effect when the vsync signal arrives at a certain Video
Port.
If two threads for two display output choose to update these two registers
simultaneously to meet their own plane adjustment requirements(change plane
zpos or switch plane from one crtc to another), then no matter which Video
Port'svsync signal we choose to follow for these two registers, the display
output of the other Video Port will be abnormal.
This is because the configuration of this Video Port does not take
effect at the right time (its configuration should take effect when its
VSYNC signal arrives).
In order to solve this problem, when performing plane migration or
change the zpos of planes, there are two things to be observed and
followed:
1. When a plane is migrated from one VP to another, the configuration of
the layer can only take effect after the Port mux configuration is
enabled.
2. When change the zpos of planes, we must ensure that the change for
the previous VP takes effect before we proceed to change the next VP.
Otherwise, the new configuration might overwrite the previous one for
the previous VP, or it could lead to the configuration of the previous
VP being take effect along with the VSYNC of the new VP.
This issue only occurs in scenarios where multi-display output is enabled.
Fixes: c5996e4ab1 ("drm/rockchip: vop2: Make overlay layer select register configuration take effect by vsync")
Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20250421102156.424480-1-andyshrk@163.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.