On Mon, Sep 08, 2025 at 07:39:07AM -0500, Mario Limonciello wrote: > > > On 9/8/25 4:19 AM, Greg Kroah-Hartman wrote: > > On Sat, Sep 06, 2025 at 09:36:31AM -0500, Mario Limonciello (AMD) wrote: > > > A variety of issues both in function and in power consumption have been > > > raised as a result of devices not being put into a low power state when > > > the system is powered off. > > > > > > There have been some localized changes[1] to PCI core to help these > > > issues, > > > but they have had various downsides. > > > > > > This series instead tries to use the S4 flow when the system is being > > > powered off. This lines up the behavior with what other operating systems > > > do as well. If for some reason that fails or is not supported, run their > > > shutdown() callbacks. > > > > > > Cc: AceLan Kao <acelan....@canonical.com> > > > Cc: Kai-Heng Feng <kaihe...@nvidia.com> > > > Cc: Mark Pearson <mpearson-len...@squebb.ca> > > > Cc: Merthan Karakaş <m3rth...@gmail.com> > > > Cc: Eric Naim <dn...@cachyos.org> > > > --- > > > v6 RESEND: > > > * Resent because Greg said he was ignoring it and would like the whole > > > series to be able to review. > > > > Messy, but wow, I'll trust you all that this actually works properly. > > Yes; I double checked from a UART log all devices (now) went to correct > state and from power measurement hardware the respective drop in power. > > I will note I have a sampling bias of hardware being x86 AMD hardware. > Some of the testers of the series also tested Intel hardware which had > similar power consumption problem, and I know there were improvements there > too. > > We probably will have to wait for linux-next for non-x86 hardware coverage. > > No objections from me, but I don't want my ack on this as I don't know > > how to maintain it :) > > > > I mean - if all goes well even a failed S4 flow should fall back to old path > shutdown. I *did contrive some failures* in an earlier version of the > series and confirmed in the UART log it emitted the printk that it was > falling back to shutdown. > > I had two ideas that maybe could help for regression risk though: > 1) I could add a shutdown= kernel parameter. I'm not sure what words to use > for the two paths but the idea would be if someone had a shutdown failure > they could isolate if it's due to this by adding the parameter. > > 2) I could make a Documentation/ file explaining some examples how to get > the shutdown log saved to pstore in case they don't have a UART available.
This second one is probably the best. A new command line is not going to probably be used and just be a pain to maintain over time. thanks, greg k-h
