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The TIDSS hardware does not have independent maximum or minimum pixel clock limits for each video port. Instead, these limits are determined by the SoC's clock architecture. Previously, this constraint was modeled using the 'max_pclk_khz' and 'min_pclk_khz' fields in 'dispc_features', but this approach is static and does not account for the dynamic behavior of PLLs. This patch removes the 'max_pclk_khz' and 'min_pclk_khz' fields from 'dispc_features'. The correct way to check if a requested mode's pixel clock is supported is by using 'clk_round_rate()' in the 'mode_valid()' hook. If the best frequency match for the mode clock falls within the supported tolerance, it is approved. TIDSS supports a 5% pixel clock tolerance, which is now reflected in the validation logic. This change allows existing DSS-compatible drivers to be reused across SoCs that only differ in their pixel clock characteristics. The validation uses 'clk_round_rate()' for each mode, which may introduce additional delay (about 3.5 ms for 30 modes), but this is generally negligible. Users desiring faster validation may bypass these calls selectively, for example, checking only the highest resolution mode, as shown here[1]. [1]: https://lore.kernel.org/all/20250704094851.182131-3-j-choudhary@ti.com/ Tested-by: Michael Walle <mwalle@kernel.org> Reviewed-by: Devarsh Thakkar <devarsht@ti.com> Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com> Signed-off-by: Swamil Jain <s-jain1@ti.com> Link: https://patch.msgid.link/20251104151422.307162-2-s-jain1@ti.com [Tomi: dropped 'inline' from check_pixel_clock] Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> |
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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.