linux-kernel - Re: [PATCH] hack to debug acpiphp crash

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Message-ID: <20230725135840.1edbbf61@imammedo.users.ipa.redhat.com>
Date:   Tue, 25 Jul 2023 13:58:40 +0200
From:   Igor Mammedov <imammedo@...hat.com>
To:     Woody Suwalski <terraluna977@...il.com>
Cc:     linux-kernel@...r.kernel.org, bhelgaas@...gle.com,
        linux-pci@...r.kernel.org, mst@...hat.com
Subject: Re: [PATCH] hack to debug acpiphp crash

On Tue, 25 Jul 2023 07:45:08 -0400
Woody Suwalski <terraluna977@...il.com> wrote:

> Igor Mammedov wrote:
> > On Tue, 25 Jul 2023 10:06:44 +0200
> > Igor Mammedov <imammedo@...hat.com> wrote:
> >  
> >> PS:
> >> What happens is that on resume firmware (likely EC),
> >> issues ACPI bus check on root ports which (bus check) is
> >> wired to acpiphp module (though pciehp module was initialized
> >> at boot to manage root ports), it's likely firmware bug.
> >>
> >> I'd guess the intent behind this was to check if PCIe devices
> >> were hotplugged while laptop has been asleep, and for
> >> some reason they didn't use native PCIe hotplug to handle that.
> >> However looking at laptop specs you can't hotplug PCIe
> >> devices via external ports. Given how old laptop is
> >> it isn't going to be fixed, so we would need a workaround
> >> or fixup DSDT to skip buscheck.
> >>
> >> The options I see is to keep old kernel as for such case,
> >> or bail out early from bus check/enable_slot since root port
> >> is managed by pciehp module (and let it handle hotplug).  
> > scratch all of above out (it's wrong). Looking at DSDT
> > firmware sends Notify(rpxx, 2 /* Wake */) event. Which
> > according to spec needs to be handed down to the native
> > device driver.
> >
> >  
> I agree that this laptop is a tricky one. I had to adjust my kernel 
> config NOHZ just to make it suspend to ram, otherwise it was waking back 
> right after going to sleep (and the same nohz kernel worked on all my 
> other machines)...

Blaming laptop is likely red herring in this case after some more reading.
Anyways I've just sent a new round of patches to test.