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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250526-refined-dog-of-blizzard-b48f11@houat>
Date: Mon, 26 May 2025 19:30:35 +0200
From: Maxime Ripard <mripard@...nel.org>
To: Michael <michael@...sekall.de>
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

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

Download attachment "signature.asc" of type "application/pgp-signature" (274 bytes)