linux-kernel - Re: [PATCH -v5 3/3] PCIe, PM, Add PCIe runtime D3cold support

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Message-Id: <201206162309.02170.rjw@sisk.pl>
Date:	Sat, 16 Jun 2012 23:09:01 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	huang ying <huang.ying.caritas@...il.com>
Cc:	Michał Mirosław <mirq-linux@...e.qmqm.pl>,
	Jesse Barnes <jesse.barnes@...el.com>,
	Huang Ying <ying.huang@...el.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, ming.m.lin@...el.com,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-pm@...r.kernel.org, Zheng Yan <zheng.z.yan@...el.com>
Subject: Re: [PATCH -v5 3/3] PCIe, PM, Add PCIe runtime D3cold support

On Saturday, June 16, 2012, huang ying wrote:
> On Sat, Jun 16, 2012 at 5:21 AM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> [snip]
> >
> > > @@ -731,9 +791,13 @@ int pci_set_power_state(struct pci_dev *
> > >  {
> > >       int error;
> > >
> > > -     /* bound the state we're entering */
> > > -     if (state > PCI_D3hot)
> > > +     /* D3cold during system suspend/hibernate is not supported */
> > > +     if (!dev->runtime_d3cold && state > PCI_D3hot)
> >
> > I don't think this is the right place for the dev->runtime_d3cold check,
> > I've already told you that and haven't heard anything from you causing me
> > to change my mind.
> >
> > If you don't want D3cold to be used during system sleep transitions,
> > please make sure that D3cold is not passed to pci_set_power_state() in
> > those cases.
> >
> 
> OK.  Checked pci_set_power_state usage with following command line:
> 
> $ grep 'pci_set_power_state' -r . | grep -v PCI_D3hot | grep -v PCI_D0 |
> grep -v pci_choose_state
> $ grep 'pci_set_power_state' -r . | grep -v PCI_D3hot | grep -v PCI_D0 |
> grep -v pci_choose_state | grep -i d3cold
> 
> Found that, almost all pci_set_power_state usage is:
> 
> 1) set to PCI_Dx (not PCI_D3cold)
> 2) set to the state that choosed by pci_choose_state()
> 3) driver use pci_prepare_to_sleep(), which will call pci_set_power_state()
> 
> The only two exceptions are as follow:
> 
> ./drivers/misc/cb710/core.c:            pci_set_power_state(pdev,
> PCI_D3cold);
> ./arch/x86/pci/mrst.c:  pci_set_power_state(dev, PCI_D3cold);

Well, no one is supposed to pass PCI_D3cold to pci_set_power_state() before
the $subject patch, so they should be fixed anyway.

> And pci_choose_state() will not return PCI_D3cold for system suspend.
> 
> So what do you think about the following solution?
> 
> a) Change pci_prepare_to_sleep(), so that it will not put device into
> PCI_D3cold.
> b) Change PCI_D3cold to PCI_D3hot in the following two places,
> 
> ./drivers/misc/cb710/core.c:            pci_set_power_state(pdev,
> PCI_D3cold);
> ./arch/x86/pci/mrst.c:  pci_set_power_state(dev, PCI_D3cold);

Yes, that will do.

Thanks,
Rafael
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