Thanks once again! We are getting closer to find out where the problem lies!
The RC5 DRM log shows that Xe selects native PCH PWM backlight control based on the VBT. Brightness changes reach the driver, and PWM values are written and read back correctly, but the OLED panel does not physically respond. The panel advertises VESA AUX/DPCD brightness support, but this interface is not selected automatically. This strongly suggests that the firmware describes the wrong physical control method. The next diagnostic step is a temporary RC5 boot with xe.enable_dpcd_backlight=2 to force VESA AUX control. So basically, the test is going to look exactly as before, just with new boot parameter included: xe.enable_dpcd_backlight=2 drm.debug=0x1e log_buf_len=4M Later on check: uname -r cat /proc/cmdline cat /sys/module/xe/parameters/enable_dpcd_backlight And collect the logs after performing brightness 20/80% test: sudo journalctl -b -k --no-pager > ~/brightness-rc5-vesa-drm.log -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2163244 Title: Ubuntu 26.04 LTS -- Lenovo Yoga 7 Pro 15IPH11 Screen Brightness not Working To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2163244/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
