panel-simple-dp-aux: "DP AUX done_probing() can't defer" on MT8186 w/ Collabora kernel

[Dmitry Baryshkov]

On Sat, Jul 27, 2024 at 08:33:10PM GMT, Alper Nebi Yasak wrote:
> Hi,
> 
> I have a MT8186 "Magneton" Chromebook that I'm trying to boot a kernel
> based on Collabora's for-kernelci branch [1], using a config from
> postmarketOS [2] (intended for that), on a Debian sid installation.
> This sometimes fails to enable the display with:
> 
> > panel-simple-dp-aux aux-0-0058: DP AUX done_probing() can't defer

The error is caused by mtk_dp_edp_link_panel() returning -EPROBE_DEFER
(most likely because something is missing). However this callback must
not defer, it's called at at a different point.

The actual issue seems to be in these lines. The callback tries to bind
all components, however it should not as the DPI isn't available yet.

[drm:drm_bridge_attach] *ERROR* failed to attach bridge /soc/dpi at 1400a000 to encoder TMDS-32: -517
[drm:mtk_dsi_host_attach] *ERROR* failed to add dsi_host component: -517
anx7625 0-0058: [drm:anx7625_link_bridge] *ERROR* fail to attach dsi to host.

> 
> I know this is a weird out-of-tree combination of things but I've been
> asked to report this on the mailing list by wens on the #linux-mediatek
> IRC channel.
> 
> [1] https://gitlab.collabora.com/google/chromeos-kernel/-/commits/for-kernelci/
> 
> [2] https://gitlab.com/postmarketOS/pmaports/-/blob/master/device/testing/linux-postmarketos-mediatek-mt81xx/config-postmarketos-mediatek-mt81xx.aarch64
> 
> Serial output from the system starting with dmesg and some more info copied below.


[trimmed the log]

-- 
With best wishes
Dmitry