linux-kernel - Re: [PATCH v5 3/4] PCI: Decouple D3Hot and D3Cold handling for bridges

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Message-ID: <20240820234504.GA231828@bhelgaas>
Date: Tue, 20 Aug 2024 18:45:04 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: Oliver Neukum <oneukum@...e.com>, Bjorn Helgaas <bhelgaas@...gle.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	lukas@...ner.de, mika.westerberg@...ux.intel.com,
	Hsin-Yi Wang <hsinyi@...omium.org>
Subject: Re: [PATCH v5 3/4] PCI: Decouple D3Hot and D3Cold handling for
 bridges

On Tue, Aug 20, 2024 at 11:30:08AM +0530, Manivannan Sadhasivam wrote:
> On Mon, Aug 19, 2024 at 02:44:43PM +0200, Oliver Neukum wrote:
> > On 02.08.24 07:55, Manivannan Sadhasivam via B4 Relay wrote:
> > 
> > > --- a/drivers/pci/pci-acpi.c
> > > +++ b/drivers/pci/pci-acpi.c
> > > @@ -1434,7 +1434,7 @@ void pci_acpi_setup(struct device *dev, struct acpi_device *adev)
> > >   	 * reason is that the bridge may have additional methods such as
> > >   	 * _DSW that need to be called.
> > >   	 */
> > > -	if (pci_dev->bridge_d3_allowed)
> > > +	if (pci_dev->bridge_d3cold_allowed && pci_dev->bridge_d3hot_allowed)
> > 
> > Are you sure you want to require both capabilities here?
> 
> Wakeup is common for both D3Hot and D3Cold, isn't it?

>From a spec point of view, moving device from D3hot to D0 is a config
space write that the OS knows how to do, but moving a device from
D3cold to D0 requires some platform-specific magic.  If that's what
you mean by wakeup, they don't look common to me.

Bjorn