Thank you again for running these tests and for providing the EDID file. The results clarify what is happening.
The laptop exposes two possible ways to control the internal screen brightness: 1. In automatic mode, the kernel follows the firmware information and selects PWM brightness control. The brightness value changes in Ubuntu, but the physical OLED panel does not react. 2. With xe.enable_dpcd_backlight=2, the kernel uses VESA AUX brightness control through the eDP connection. The physical screen responds immediately after startup. This confirms that VESA AUX is the functional brightness-control method for this panel. The EDID file is valid and identifies the panel as EDO EF25QBA63.B. Its DisplayID data reports: - Maximum full-screen luminance: 507.5 cd/m² - Maximum luminance for a small 10% area: 1100 cd/m² - Minimum luminance: 0.000170 cd/m² The current kernel does not use the reported full-screen limit. It falls back to a range of 0 to 512 instead. Sending values close to or above the panel's declared maximum is a likely explanation for the significant dimming at the very end of the slider. This still needs confirmation in a kernel that reads the DisplayID range correctly. The flatter behavior beginning around 93% may be related, but it is not yet fully explained. A permanent kernel solution therefore appears to require two separate corrections: - Automatically select VESA AUX instead of the non-functional PWM method on this laptop and panel. - Use the luminance range reported in DisplayID instead of the fallback maximum of 512. For now, xe.enable_dpcd_backlight=2 remains a temporary workaround. Since the final part of the slider behaves incorrectly, please avoid setting it to the highest few percent. There are two possible paths to a permanent fix. Lenovo could correct the BIOS/VBT, which currently tells Linux to use a non-functional PWM interface. Alternatively, the upstream Linux DRM/Xe driver could add a narrow workaround to select VESA AUX automatically and use the luminance limits reported by DisplayID. I recommend pursuing both paths. The panel EDID itself is valid, so this does not appear to be a panel firmware problem. -- 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
