Re: [PATCH 9/9] [DO NOT MERGE] drm/sun4i: rgb: Add 5% tolerance to dot clock frequency check

Vasily Khoruzhick
2019-02-03T01:32:42Z

On Thu, Oct 18, 2018 at 4:31 AM Laurent Pinchart
<laurent.pinchart-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org> wrote:

> Given that the tolerance is a property of the panel or bridge, I agree with
> Daniel that it should be implemented there, or at least in cooperation with
> drm_panel and drm_bridge.

Clock tolerance is not specified in ANX6345 datasheet.

> Semi-related information, I think the CEA and VESA standards allow a 0.5%
> clock tolerance. What is the maximum clock frequency deviation required for
> this platform ?

This particular platform requires ~1% deviation.

E.g. on Pinebook with 768p panel: requested clock: 73.0 MHz, real
clock: 72.296296 MHz (0.96%)
on Pinebook with 1080p panel: requested clock: 138.5 MHz, real clock:
138.461538 MHz (0.03%)

So unfortunately 0.5% is not enough.

Regards,
Vasily