[Bug 211807] [drm:drm_dp_mst_dpcd_read] *ERROR* mstb 000000004e6288dd port 3: DPCD read on addr 0x60 for 1 bytes NAKed

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=211807

Chatty (mail@chatty.de) changed:

           What    |Removed                     |Added
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                 CC|                            |mail@chatty.de

--- Comment #17 from Chatty (mail@chatty.de) ---
My setup: MS Surface Book 2 + AOC U2879G6 via Surface Dock via DisplayPort
Tested kernels: 5.10.0 / 5.15.3 / 5.16.0-rc1

When connecting I get random results of:
* monitor remains black
* monitor exhibits 1080p@60 as max resolution
* monitor exhibits 1440p@60 as max resolution
* monitor exhibits 2160p@30 as max resolution
* monitor exhibits 2160p@30 as max resolution <== desired

On boot of 5.16.0-rc1 its initialized with:
> i915 0000:00:02.0: [drm] Finished loading DMC firmware
> i915/kbl_dmc_ver1_04.bin (v1.4)
> [drm] Initialized i915 1.6.0 20201103 for 0000:00:02.0 on minor 0

In the first case I see following dmesg output (black monitor):
> i915 0000:00:02.0: [drm] *ERROR* mstb 0000000009cd3ca6 port 1: DPCD read on
> addr 0x4b0 for 1 bytes NAKed

In the last case I see following dmesg output (despite monitor working):
> i915 0000:00:02.0: [drm] *ERROR* mstb 00000000f4b4c9f1 port 1: DPCD read on
> addr 0x4b0 for 1 bytes NAKed
> i915 0000:00:02.0: [drm] *ERROR* mstb 00000000f4b4c9f1 port 1: DPCD read on
> addr 0x4b0 for 1 bytes NAKed
> i915 0000:00:02.0: [drm] *ERROR* mstb 00000000f4b4c9f1 port 1: DPCD read on
> addr 0x4b0 for 1 bytes NAKed
> i915 0000:00:02.0: [drm] *ERROR* mstb 00000000f4b4c9f1 port 1: DPCD read on
> addr 0x4b0 for 1 bytes NAKed
> i915 0000:00:02.0: [drm] *ERROR* mstb 00000000f4b4c9f1 port 1: DPCD read on
> addr 0x4b0 for 1 bytes NAKed

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