Re: [PATCH 00/13] imx8mp: first clock propagation attempt (for LVDS)

[Benjamin Bara]

Hi Frank!

On Mon, 18 Sept 2023 at 19:24, Frank Oltmanns <frank@xxxxxxxxxxxx> wrote:
> On 2023-09-18 at 00:39:56 +0200, Benjamin Bara <bbara93@xxxxxxxxx> wrote:
> Thank you very much for including me in the discussion. If I understood
> Maxime correctly, your proposal is close to what he was suggesting in
> the discussion you referenced. Unfortunately, it doesn't cover the
> rounding aspect (which you also mentioned in your cover letter and the
> description for clk_detect_unintended_rate_changes in patch 7. I've been
> pondering the last three weeks how to find a good solution to this
> problem, but so far haven't found any.

I think if we stick to the idea of always enforcing the exact "typical
rate", we cannot avoid physically impossible cases. IMHO, it might make
sense to add a set_rate() function with a "timing_entry" (e.g. used by
display_timing.h[1]) to the clock API, which gives a suggestion but also
defines the "real" boundaries. This would provide a shared parent PLL
more freedom to provide a satisfying rate for all its children.

Regards
Benjamin

[1] https://elixir.bootlin.com/linux/v6.5.3/source/include/video/display_timing.h#L64