linux-kernel - Re: [PATCH v2] drm/edid: add 6 bpc quirk to the Sharp LQ116M1JW10

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Message-ID: <CAD=FV=XqgkgLLOeozooypbwiO-8j0ZNy_GJ1UD2sXL1EKzC=Fw@mail.gmail.com>
Date: Mon, 3 Nov 2025 08:38:24 -0800
From: Doug Anderson <dianders@...omium.org>
To: Ajye Huang <ajye_huang@...pal.corp-partner.google.com>
Cc: linux-kernel@...r.kernel.org, Jani Nikula <jani.nikula@...el.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Jessica Zhang <jesszhan0024@...il.com>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	dri-devel@...ts.freedesktop.org, jazhan@...gle.com
Subject: Re: [PATCH v2] drm/edid: add 6 bpc quirk to the Sharp LQ116M1JW10

Hi,

On Fri, Oct 31, 2025 at 9:01 PM Ajye Huang
<ajye_huang@...pal.corp-partner.google.com> wrote:
>
> The Sharp LQ116M1JW105 reports that it supports 8 bpc modes,
> but it will happen display noise in some videos.
> So, limit it to 6 bpc modes.
>
> Signed-off-by: Ajye Huang <ajye_huang@...pal.corp-partner.google.com>
> ---
> changes from v1->v2:
> * Change EDID_QUIRK_FORCE_6BPC to BIT(EDID_QUIRK_FORCE_6BPC)
>
>  drivers/gpu/drm/drm_edid.c | 3 +++
>  1 file changed, 3 insertions(+)

There was some extra testing and summarization on the internal
discussion about this problem that cleared up my confusion and I agree
that this is the right fix. While the panel does properly link train
at 8bpp and generally displays images OK, showing certain images on
the screen displays consistent corruption on just this panel (other
8bpp panels are fine). It seems like there's some sort of subtle bug
in the panel at 8bpp. Limiting it to 6bpp, which is what the panel was
originally tested with, is the right thing to do.

Reviewed-by: Douglas Anderson <dianders@...omium.org>