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Re: [PATCH] q35: turn off power_controller_present when acpi hotplug is


From: Gerd Hoffmann
Subject: Re: [PATCH] q35: turn off power_controller_present when acpi hotplug is enabled
Date: Wed, 17 Nov 2021 09:22:20 +0100

On Tue, Nov 16, 2021 at 08:26:41PM +0100, Igor Mammedov wrote:
> On Tue, 16 Nov 2021 10:04:33 +0100
> Gerd Hoffmann <kraxel@redhat.com> wrote:
> 
> > Disable power control for pcie slots in case acpi hotplug is enabled
> > (6.2+ only for compatibility reasons).  This makes sure we don't get
> > unpleasant surprises with pci devices not being functional due to slot
> > power being turned off.
> > 
> > Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> > ---
> >  hw/i386/pc_q35.c | 13 ++++++++++---
> >  1 file changed, 10 insertions(+), 3 deletions(-)
> > 
> > diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> > index e1e100316d93..869ca4c130f0 100644
> > --- a/hw/i386/pc_q35.c
> > +++ b/hw/i386/pc_q35.c
> > @@ -247,9 +247,16 @@ static void pc_q35_init(MachineState *machine)
> >                                                   "x-keep-pci-slot-hpc",
> >                                                   NULL);
> >  
> > -    if (!keep_pci_slot_hpc && acpi_pcihp) {
> > -        object_register_sugar_prop(TYPE_PCIE_SLOT, "x-native-hotplug",
> > -                                   "false", true);
> > +    if (acpi_pcihp) {
> > +        if (keep_pci_slot_hpc) {
> > +            /* 6.2+ default: acpi-hotplug=on native-hotplug=on 
> > power-ctrl=off */
> > +            object_register_sugar_prop(TYPE_PCIE_SLOT, COMPAT_PROP_PCP,
> > +                                       "false", true);
> 
> that will also turn off COMPAT_PROP_PCP on ports attached to PXBs,
> where ACPI hotplug is not used and native one is active.

Oh, wasn't aware of that detail.

> So question is if it's expected behavior?

Nope.  When native hotplug is used slot power control should be enabled.

Not sure how to handle that best though ...

take care,
  Gerd




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