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cdns_dsi_adjust_phy_config() is called from cdns_dsi_check_conf(), which is called from .atomic_check(). It checks the DSI htotal and adjusts it to align on the DSI lane boundary by changing hfp and then recalculating htotal and HS clock rate. This has a few problems. First is the fact that the whole thing is not needed: we do not need to align on the lane boundary. The whole frame is sent in HS mode, and it is fine if the line's last byte clock tick fills, say, only 2 of the 4 lanes. The next line will just continue from there. Assuming the DSI timing values have been calculated to match the incoming DPI stream, and the HS clock is compatible with the DPI pixel clock, the "uneven" DSI lines will even out when multiple lines are being sent. But we could do the align, aligning is not a problem as such. However, adding more bytes to the hfp, as the function currently does, makes the DSI line time longer, so the function then adjusts the HS clock rate. This is where things fail: we don't know what rates we can get from the HS clock, and at least in TI K3 SoC case the rates are quite coarsely grained. Thus small adjustment to hfp will lead to a big change in HS clock rate, and things break down. We could do a loop here, adjusting hfp, adjusting clock, checking clock rate, adjusting hfp again, etc., but considering that the whole adjustment shouldn't be needed at all, it's easier to just remove the function. Something like this function should be added back later, when adding burst mode support, but that's a bigger change and I don't think this function would help that work in any way. 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-v5-9-e61cc06074c2@ideasonboard.com 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.