[REGRESSION] [BISECTED] drm/sun4i: hdmi: No HDMI output with BananaPI M1 on 6.9

[Maxime Ripard]

Hi,

On Mon, May 12, 2025 at 10:27:06PM +0200, Michael wrote:
> with v6.9 and later there is no output on the BananaPI HDMI connector.
> 
> I have bisected the issue to the following commit:
> 
>   358e76fd613a ("drm/sun4i: hdmi: Consolidate atomic_check and mode_valid")
> 
> With this patch, sun4i_hdmi_connector_clock_valid() is occasionally called
> with clock=0, causing the function to return MODE_NOCLOCK.
> In the old sun4i_hdmi_mode_valid() before the patch, mode->clock is
> always!=0, maybe that gives someone a hint.

This doesn't make sense to me, if only because the two callers of
tmds_char_rate_valid (hdmi_compute_clock and
drm_hdmi_connector_mode_valid) have, right before calling it, checks to
make sure the clock rate isn't 0, and would return MODE_ERROR or EINVAL
in such a case.

https://elixir.bootlin.com/linux/v6.15/source/drivers/gpu/drm/display/drm_hdmi_state_helper.c#L234
https://elixir.bootlin.com/linux/v6.15/source/drivers/gpu/drm/display/drm_hdmi_state_helper.c#L553

Do you have some logs (with dri.devel=0xff)? Does it happen with 6.15 as
well?

Maxime
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