Re: Commit d6e25b3590 breaks external video (HDMI) on mt8173 (chromebook oak)

[Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com>]

Hi Andy,

On Thu, 2025-08-14 at 22:38 +0800, Chun-Kuang Hu wrote:
> Forward to dri-devel and linux-mediatek.
> 
> Andy Chernyak <andy.chernyak@gmail.com> 於 2025年7月2日 週三 下午11:12寫道：
> > 
> > Kernel 6.16 has external video (both hdmi and displayport-over-
> > usbc) broken (black screen) on mt8173-based chromebooks (platform
> > codename "oak", device codename "hana"). Bisect points finger to
> > following commit:
> > 
> > From d6e25b3590a0679bca1a1becc04e3999f1dfd461
> > From: Guillaume Ranquet <granquet@baylibre.com>
> > Date: Tue, 15 Apr 2025 12:43:05 +0200
> > Subject: drm/mediatek: hdmi: Use regmap instead of iomem for main
> > registers
> > In preparation for the addition of a new version of the HDMI IP
> > which will need to share its iospace between multiple subdrivers,
> > and in preparation for moving out the common bits between the two,
> > migrate this driver to fully use regmap.
> > 
> > Reverting d6e25b3590 with "patch -R" on top of 6.16-rc4 fixes this.

thank you for the bug report.

By reading and checking this patch changes, I found two modifications
that looked incorrect, so I sent a patch to fix them:
https://lore.kernel.org/dri-devel/20250818-mt8173-fix-hdmi-issue-v1-1-55aff9b0295d@collabora.com/

Since I don't have any mt8173-based board myself, could you test this
patch and tell if it does fix the issue (or not)?

Looking forward to your reply,

Regards,
Louis-Alexis