This regression was introduced in commit "7627a0edef54." It appears that ahci.c is setting non-host controller devices (in this case, Intel VGA) to ATA_LPM_MIN_POWER, which causes buffer underruns in the Intel iGPU on i7-9700 systems, rendering the display unusable in most cases (129 out of 132 boots). Currently, this can be fixed with the kernel parameter `ahci.mobile_lpm_policy=0` as a workaround. Related Issues: - https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14213 - https://github.com/qubesos/qubes-issues/issues/9887 ### Bisect History on stable/linux. ``` 480e035fc4c7 -> BAD e5e038b7ae9d -> BAD ... 07abb19a9b20 -> BAD ... 6cdebf62a159 -> BAD ... 57aaf9134c03 -> BAD <<< a9dde2823c33^..7edbb6059274 -> BAD ... ^..7627a0edef54 -> BAD <<< ... ^..ae1f3db006b7 -> GOOD 7d62cb2a59f4 -> GOOD 8c9c2f851b5a -> GOOD ... f88c3fb81c4b -> GOOD ... 216532e147b2 -> GOOD ... e66c58f74351 -> GOOD ```
Based on the kernel log, it appears that the AHCI is correctly recognizing the device; it _doesn't_ change anything about the iGPU itself. But somehow, it seems that setting the AHCI device to ATA_LPM_MIN_POWER is causing the integrated GPU not to function correctly. I'm not sure if this issue is specific to the ASUSPRO-D840SA or if it affects all i7-9700 systems. I'm quite confused about this.