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

[bugzilla-daemon at bugzilla.kernel.org]

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

Matt Berry (matthew.william.berry at gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |matthew.william.berry at gmail
                   |                            |.com

--- Comment #11 from Matt Berry (matthew.william.berry at gmail.com) ---
I'm seeing this when I use my work laptop (HP SKU 3YG73UC) with a Startech DP
KVM (sv231dpu2) on Ubuntu 20.04 (5.11.0-37-generic). It doesn't happen every
time, but when I switch the KVM over I'll hear the fan kick on and when I
switch the KVM back I'll see the following in `dmesg`. Given that it's a work
laptop, I'll have to follow their kernel release cycle, but will report back if
I see it on newer kernels as they roll out.

```
sudo journalctl -b 0 | grep -i firmware | grep i915
Oct 12 14:44:59 u41fc3826021951.ant.amazon.com kernel: i915 0000:00:02.0: [drm]
Finished loading DMC firmware i915/kbl_dmc_ver1_04.bin (v1.4)

sudo dmesg | egrep -vi 'audit|usb |hub |input: '
[941754.942373] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 1: DPCD read on addr 0x4b0 for 1 bytes NAKed
[941754.964462] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 3: DPCD read on addr 0x4b0 for 1 bytes NAKed
[941953.993504] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 3: DPCD read on addr 0x4b0 for 1 bytes NAKed
[942109.330113] loop12: detected capacity change from 0 to 1232
[942125.974833] loop13: detected capacity change from 0 to 337424
[942146.986960] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 3: DPCD read on addr 0x4b0 for 1 bytes NAKed
[942392.995237] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 3: DPCD read on addr 0x4b0 for 1 bytes NAKed
[942967.950060] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 1: DPCD read on addr 0x4b0 for 1 bytes NAKed
[942967.972573] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 3: DPCD read on addr 0x4b0 for 1 bytes NAKed
[942990.984072] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 3: DPCD read on addr 0x4b0 for 1 bytes NAKed
[943003.939382] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 1: DPCD read on addr 0x4b0 for 1 bytes NAKed
[943003.962504] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 3: DPCD read on addr 0x4b0 for 1 bytes NAKed
[943227.981538] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 3: DPCD read on addr 0x4b0 for 1 bytes NAKed
[943765.979086] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 3: DPCD read on addr 0x4b0 for 1 bytes NAKed
[943775.950453] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 1: DPCD read on addr 0x4b0 for 1 bytes NAKed
[943775.981195] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 3: DPCD read on addr 0x4b0 for 1 bytes NAKed
[944033.975975] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 3: DPCD read on addr 0x4b0 for 1 bytes NAKed
[945830.946882] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 1: DPCD read on addr 0x4b0 for 1 bytes NAKed
[945830.969342] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 3: DPCD read on addr 0x4b0 for 1 bytes NAKed
[946098.985432] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 3: DPCD read on addr 0x4b0 for 1 bytes NAKed
[947569.935525] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 1: DPCD read on addr 0x4b0 for 1 bytes NAKed
[947569.957792] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 3: DPCD read on addr 0x4b0 for 1 bytes NAKed
[947604.971146] [drm:drm_dp_mst_dpcd_read [drm_kms_helper]] *ERROR* mstb
000000003ba372b9 port 3: DPCD read on addr 0x4b0 for 1 bytes NAKed
```

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