Bug 2511730
| Summary: | Internal display backlight/brightness broken after kernel update on Fedora 44 | ||||||
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| Product: | [Fedora] Fedora | Reporter: | Evgeni Borisov <geno1520> | ||||
| Component: | kernel | Assignee: | Justin M. Forbes <jforbes> | ||||
| Status: | NEW --- | QA Contact: | Fedora Extras Quality Assurance <extras-qa> | ||||
| Severity: | high | Docs Contact: | |||||
| Priority: | unspecified | ||||||
| Version: | 44 | CC: | acaringi, adscvr, airlied, egeorget, geno1520, hans, hpa, jforbes, jo.spam, kernel-maint, linville, masami256, mchehab, nickolasjcarr, ptalbert, steved, suraj.ghimire7, vincent.sabatini | ||||
| Target Milestone: | --- | ||||||
| Target Release: | --- | ||||||
| Hardware: | x86_64 | ||||||
| OS: | Linux | ||||||
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| Fixed In Version: | Doc Type: | --- | |||||
| Doc Text: | Story Points: | --- | |||||
| Clone Of: | Environment: | ||||||
| Last Closed: | Type: | Bug | |||||
| Regression: | --- | Mount Type: | --- | ||||
| Documentation: | --- | CRM: | |||||
| Verified Versions: | Category: | --- | |||||
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |||||
| Cloudforms Team: | --- | Target Upstream Version: | |||||
| Embargoed: | |||||||
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I have a similar issue lately, with brightness getting very low at 99% and 100%, but getting back at a ok level at 98% and lower. Could you try setting your backlight level at 95%, just to be sure our issue are the same or not ? Has been reported upstream: https://gitlab.freedesktop.org/drm/amd/-/work_items/5569 https://gitlab.freedesktop.org/drm/amd/-/work_items/5562 (In reply to egeorget from comment #1) > I have a similar issue lately, with brightness getting very low at 99% and > 100%, but getting back at a ok level at 98% and lower. Could you try setting > your backlight level at 95%, just to be sure our issue are the same or not ? I can make a test in 1-2 hours. Then will provide the results. Sorry for the delay. (In reply to Evgeni Borisov from comment #3) > (In reply to egeorget from comment #1) > > I have a similar issue lately, with brightness getting very low at 99% and > > 100%, but getting back at a ok level at 98% and lower. Could you try setting > > your backlight level at 95%, just to be sure our issue are the same or not ? > > I can make a test in 1-2 hours. Then will provide the results. > Sorry for the delay. After using #Brightnrssctl set 95% The brightnesss restored as normal. Getting back to 98% and higher the brighness became very low - almost nothing is visible. I did a binary search directly via sysfs to find the exact threshold where the panel goes dark, bypassing brightnessctl/userspace entirely: # max_brightness = 65535 echo <value> | sudo tee /sys/class/backlight/amdgpu_bl1/brightness cat /sys/class/backlight/amdgpu_bl1/actual_brightness Results: brightness written actual_brightness screen 63569 (97%) 65535 OK 63691 65535 OK 63752 65535 OK 63783 65535 OK 63790 65535 OK 63794 65535 OK 63796 65535 OK 63797 65535 OK 63798 0 DARK 63814 0 DARK 64060 0 DARK 64550 0 DARK 65534 0 DARK 65535 (100%) 0 DARK The exact threshold is between 63797 (last working value) and 63798 (first failing value). Note this is not a round percentage (63797/65535 ≈ 97.36%) nor an obvious power-of-two boundary, so it may correspond to some internal panel/DPCD scaling table or register width rather than a simple percentage cutoff. Notably, actual_brightness reads back as exactly 0 for every failing value (not a partial/dim value), suggesting the driver or panel firmware is rejecting/misinterpreting values above this threshold entirely, rather than a gradual scaling error. Confirmed fixed as of kernel 7.1.10-200.fc44.x86_64. max_brightness is now correctly reported as 62451 (previously 65535). Writing 65535 now fails with EINVAL as expected. brightnessctl set 100% now correctly sets brightness to 62451 (100%), and the screen displays normal brightness with no darkening. Minor note: actual_brightness reads back as 64310, slightly above the new max_brightness of 62451 — possibly a different internal scale for the readback value, but this does not appear to affect actual screen behavior; brightness works correctly at all levels including 100%. Thanks for the fix! |
Created attachment 2153709 [details] Extract from the previous boot, when the issue occur. 1. After a recent kernel update on Fedora 44, the internal laptop display becomes very dim / brightness is stuck at a low level. Booting into the previous kernel version restores normal brightness and behavior, confirming this is a kernel-level regression rather than a hardware or desktop-environment issue. 2. What is the Version-Release number of the kernel: Working kernel: 7.1.5-201.fc44.x86_64 Broken kernel: 7.1.6-201.fc44.x86_64 3. Did it work previously in Fedora? Yes 4. Can you reproduce this issue? If so, please provide the steps to reproduce the issue below:Always, on every boot with the affected kernel version. 5. Does this problem occur with the latest Rawhide kernel? To install the Rawhide kernel, run ``sudo dnf install fedora-repos-rawhide`` followed by ``sudo dnf update --enablerepo=rawhide kernel``: 6. Are you running any modules that not shipped with directly Fedora's kernel?:No 7. Please attach the kernel logs. You can get the complete kernel log for a boot with ``journalctl --no-hostname -k > dmesg.txt``. If the issue occurred on a previous boot, use the journalctl ``-b`` flag.