Tomi Valkeinen be9fc98a41 drm/bridge: cdns-dsi: Fix REG_WAKEUP_TIME value
[ Upstream commit eea4f89b6461294ed6bea1d3285bb3f79c09a041 ]

The driver tries to calculate the value for REG_WAKEUP_TIME. However,
the calculation itself is not correct, and to add on it, the resulting
value is almost always larger than the field's size, so the actual
result is more or less random.

According to the docs, figuring out the value for REG_WAKEUP_TIME
requires HW characterization and there's no way to have a generic
algorithm to come up with the value. That doesn't help at all...

However, we know that the value must be smaller than the line time, and,
at least in my understanding, the proper value for it is quite small.
Testing shows that setting it to 1/10 of the line time seems to work
well. All video modes from my HDMI monitor work with this algorithm.

Hopefully we'll get more information on how to calculate the value, and
we can then update this.

Tested-by: Parth Pancholi <parth.pancholi@toradex.com>
Tested-by: Jayesh Choudhary <j-choudhary@ti.com>
Reviewed-by: Devarsh Thakkar <devarsht@ti.com>
Link: https://lore.kernel.org/r/20250723-cdns-dsi-impro-v5-11-e61cc06074c2@ideasonboard.com
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2025-11-24 10:29:26 +01:00
2025-11-02 22:14:42 +09:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
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In order to build the documentation, use ``make htmldocs`` or
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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.
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