On Mon, 1 Jan 2024, Bjorn Helgaas wrote: > On Mon, Dec 25, 2023 at 07:29:02PM +0100, Michael Schaller wrote: > > Issue: > > On resume from suspend to RAM there is no output for about 12 seconds, then > > shortly a blinking cursor is visible in the upper left corner on an > > otherwise black screen which is followed by a reboot. > > > > Setup: > > * Machine: ASUS mini PC PN51-BB757MDE1 (DMI model: MINIPC PN51-E1) > > * Firmware: 0508 (latest; also tested previous 0505) > > * OS: Ubuntu 23.10 (except kernel) > > * Kernel: 6.6.8 (also tested 6.7-rc7; config attached) > > > > Debugging summary: > > * Kernel 5.10.205 isn’t affected. > > * Bisect identified commit 08d0cc5f34265d1a1e3031f319f594bd1970976c as > > cause. > > * PCI device 0000:03:00.0 (Intel 8265 Wifi) causes resume issues as long as > > ASPM is enabled (default). > > * The commit message indicates that a quirk could be written to mitigate the > > issue but I don’t know how to write such a quirk. > > > > Confirmed workarounds: > > * Connect a USB flash drive (no clue why; maybe this causes a delay that > > lets the resume succeed) > > * Revert commit 08d0cc5f34265d1a1e3031f319f594bd1970976c (commit seemed > > intentional; a quirk seems to be the preferred solution) > > * pcie_aspm=off > > * pcie_aspm.policy=performance > > * echo 0 | sudo tee /sys/bus/pci/devices/0000:03:00.0/link/l1_aspm > > > > Debugging details: > > * The resume trigger (power button, keyboard, mouse) doesn’t seem to make > > any difference. > > * Double checked that the kernel is configured to *not* reboot on panic. > > * Double checked that there still isn't any kernel output without quiet and > > splash. > > * The issue doesn’t happen if a USB flash drive is connected. The content of > > the flash drive doesn’t appear to matter. The USB port doesn’t appear to > > matter. > > * No information in any logs after the reboot. I suspect the resume from > > suspend to RAM isn’t getting far enough as that logs could be written. > > * Kernel 5.10.205 isn’t affected. Kernel 5.15.145, 6.6.8 and 6.7-rc7 are > > affected. > > * A kernel bisect has revealed the following commit as cause: > > https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=08d0cc5f34265d1a1e3031f319f594bd1970976c > > * The commit was part of kernel 5.20 and has been backported to 5.15. > > * The commit mentions that a device-specific quirk could be added in case of > > new issues. > > * According to sysfs and lspci only device 0000:03:00.0 (Intel 8265 Wifi) > > has ASPM enabled by default. > > * Disabling ASPM for device 0000:03:00.0 lets the resume from suspend to RAM > > succeed. > > * Enabling ASPM for all devices except 0000:03:00.0 lets the resume from > > suspend to RAM succeed. > > * This would indicate that a quirk is missing for the device 0000:03:00.0 > > (Intel 8265 Wifi) but I have no clue how to write such a quirk or how to get > > the specifics for such a quirk. > > * I still have no clue how a USB flash drive plays into all this. Maybe some > > kind of a timing issue where the connected USB flash drive delays something > > long enough so that the resume succeeds. Maybe the code removed by commit > > 08d0cc5f34265d1a1e3031f319f594bd1970976c caused a similar delay. ¯\_(ツ)_/¯ > > Hmmm. 08d0cc5f3426 ("PCI/ASPM: Remove pcie_aspm_pm_state_change()") > appeared in v6.0, released Oct 2, 2022, so it's been there a while. > > But I think the best option is to revert it until this issue is > resolved. Per the commit log, 08d0cc5f3426 solved two problems: > > 1) ASPM config changes done via sysfs are lost if the device power > state is changed, e.g., typically set to D3hot in .suspend() and > D0 in .resume(). > > 2) If L1SS is restored during system resume, that restored state > would be overwritten. > > Problem 2) relates to a patch that is currently reverted (a7152be79b62 > ("Revert "PCI/ASPM: Save L1 PM Substates Capability for > suspend/resume""), so I don't think reverting 08d0cc5f3426 will make > this problem worse. > > Reverting 08d0cc5f3426 will make 1) a problem again. But my guess is > ASPM changes via sysfs are fairly unusual and the device probably > remains functional even though it may use more power because the ASPM > configuration was lost. > > So unless somebody has a counter-argument, I plan to queue a revert of > 08d0cc5f3426 ("PCI/ASPM: Remove pcie_aspm_pm_state_change()") for > v6.7. Hi, I cannot understand how 1) even occurs. AFAICT, nothing pcie_aspm_pm_state_change() calls into overwrites link->aspm_disable that is the variable storing user inputs via sysfs. So how the changes via sysfs are lost? -- i.
