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

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Message-ID: <aD3wE_mkfYA2XqA6@a98shuttle.de>
Date: Mon, 2 Jun 2025 20:40:19 +0200
From: Michael Klein <michael@...sekall.de>
To: Maxime Ripard <mripard@...nel.org>
Cc: Chen-Yu Tsai <wens@...e.org>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	Samuel Holland <samuel@...lland.org>,
	dri-devel@...ts.freedesktop.org,
	linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
	linux-kernel@...r.kernel.org, regressions@...ts.linux.dev
Subject: Re: [REGRESSION] [BISECTED] drm/sun4i: hdmi: No HDMI output with
 BananaPI M1 on 6.9

On Mon, Jun 02, 2025 at 11:55:44AM +0200, Maxime Ripard wrote:
>On Mon, May 26, 2025 at 11:13:01PM +0200, Michael wrote:
>> On Mon, May 26, 2025 at 07:30:35PM +0200, Maxime Ripard wrote:
>> > 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
>>
>> Before 6.14, sun4i_hdmi_connector_clock_valid() was also called from
>> sun4i_hdmi_connector_atomic_check()...
>>
>> > Do you have some logs (with dri.devel=0xff)? Does it happen with 6.15 as
>> > well?
>>
>> It does not happen with 6.15, as it was fixed in 6.14 with 84e541b1e58e
>> ("drm/sun4i: use drm_atomic_helper_connector_hdmi_check()").
>
>Then we might still need to backport that patch.
>
>Does applying it to 6.9 alone makes it work, or do you need some additional ones (I'm thinking of
>ae048fc4f96d in particular, which in turn would require 47368ab437fd)

No way to apply this to anything 6.9. The closest I can get it into is 
6.11, which requires both ae048fc4f96d and 47368ab437fd (with one 
trivial conflict) to make it work. Anthing earlier lacks the entire HDMI 
connector framework.

-- 
Michael