Bug 213715 - failed to change brightness of HDR panel on AMD GREEN_SARDINE through aux
Summary: failed to change brightness of HDR panel on AMD GREEN_SARDINE through aux
Status: NEW
Alias: None
Product: Drivers
Classification: Unclassified
Component: Video(DRI - non Intel) (show other bugs)
Hardware: All Linux
: P1 blocking
Assignee: drivers_video-dri
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2021-07-13 16:27 UTC by Pengyu Ma
Modified: 2021-07-20 16:08 UTC (History)
2 users (show)

See Also:
Kernel Version: 5.14.0-rc1+
Subsystem:
Regression: No
Bisected commit-id:

Attachments
dmesg (475.32 KB, text/plain)
2021-07-13 16:27 UTC, Pengyu Ma 		Details
4k display edid (256 bytes, application/octet-stream)
2021-07-13 16:29 UTC, Pengyu Ma 		Details
Add an attachment (proposed patch, testcase, etc.)

Description Pengyu Ma 2021-07-13 16:27:24 UTC 
Created attachment 297819 [details]
dmesg

HW: ThinkPad P14s gen 2a
CPU: AMD Ryzen 7 PRO 5850U with Radeon Graphics
Panel: BOE 2434 and  CSO 5127

brightness can't be controlled through AUX.
It works with parameter "amdgpu.backlight=0"

dmesg attached.
Comment 1 Pengyu Ma 2021-07-13 16:29:49 UTC 
Created attachment 297821 [details]
4k display edid
Comment 2 Mario Limonciello (AMD) 2021-07-20 16:08:38 UTC 
I would suggest to work with BOE and CSO to fix the DPCD values in panel firmware to not report aux control if it is not functional.

You can see the kernel checks the DPCD to determine whether to use AUX or PWM.

https://github.com/torvalds/linux/blob/c010efb7f0bc0c3cb2cd26b000f71d4bd0c427cd/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c#L2433

BTW this behavior has been also been reported in the past, so a heuristic may be introduced at some point in the future for the buggy panel firmware: https://gitlab.freedesktop.org/drm/amd/-/issues/1438
Note You need to log in before you can comment on or make changes to this bug.