Hi Rafael, Manivannan, On Thu, Mar 13, 2025 at 10:51:13AM +0530, Manivannan Sadhasivam wrote: > On Wed, Mar 05, 2025 at 02:41:26PM +0100, Rafael J. Wysocki wrote: > > There were hardware issues related to PM on x86 platforms predating > > the introduction of Connected Standby in Windows. For instance, > > programming a port into D3hot by writing to its PMCSR might cause the > > PCIe link behind it to go down and the only way to revive it was to > > power cycle the Root Complex. And similar. > > > > Also, PM has never really worked correctly on PCI (non-PCIe) bridges > > and there is this case where the platform firmware handles hotplug and > > doesn't want the OS to get in the way (the bridge->is_hotplug_bridge > > && !pciehp_is_native(bridge) check in pci_bridge_d3_possible()). > > > > The DMI check at the end of pci_bridge_d3_possible() is really > > something to the effect of "there is no particular reason to prevent > > this bridge from going into D3, but try to avoid platforms where it > > may not work". > > > > Thanks for sharing the background. This could go in the commit message IMO. Yes, thanks Rafael. This adds a bit more than the guesswork I've done so far. > > Basically, as far as I'm concerned, this check can be changed into > > something like > > > > if (!IS_ENABLED(CONFIG_X86) || dmi_get_bios_year() >= 2015) > > return true; I suppose if this harms any non-x86 BIOS systems, we can just add to bridge_d3_blacklist[]. This works for me too. > > which also requires updating the comment above it accordingly. > > > > This would have been better than the check added by the $subject patch IMV. > > Looks good to me. Brian, could you please respin incorporating the comments? Sure, will send shortly. Brian
