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Piotr Zalewski
a52dffaa46
Make video port registers nonvolatile. As DSP_CTRL register is written to twice due to gamma LUT enable bit which is set outside of the main DSP_CTRL initialization within atomic_enable (for rk356x case it is also necessary to always disable gamma LUT before writing a new LUT) there is a chance that DSP_CTRL value read-out in gamma LUT init/update code is not the one which was written by the preceding DSP_CTRL initialization code within atomic_enable. This might result in misconfigured DSP_CTRL which leads to no visual output[1]. Since DSP_CTRL write takes effect after VSYNC[1] the issue is not always present. When tested on Pinetab2 with kernel 6.14 it happenes only when DRM is compiled as a module[1]. In order to confirm that it is a timing issue I inserted 18ms udelay before vop2_crtc_atomic_try_set_gamma in atomic enable and compiled DRM as module - this has also fixed the issue. [1] https://lore.kernel.org/linux-rockchip/562b38e5.a496.1975f09f983.Coremail.andyshrk@163.com/ Reported-by: Diederik de Haas <didi.debian@cknow.org> Closes: https://lore.kernel.org/linux-rockchip/DAEVDSTMWI1E.J454VZN0R9MA@cknow.org/ Suggested-by: Andy Yan <andy.yan@rock-chips.com> Signed-off-by: Piotr Zalewski <pZ010001011111@proton.me> Tested-by: Diederik de Haas <didi.debian@cknow.org> Signed-off-by: Heiko Stuebner <heiko@sntech.de> Link: https://lore.kernel.org/r/20250706083629.140332-2-pZ010001011111@proton.me
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.