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

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Date:	Sat, 16 Jun 2012 11:30:54 +0800
From:	huang ying <huang.ying.caritas@...il.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Michał Mirosław <mirq-linux@...e.qmqm.pl>,
	Jesse Barnes <jesse.barnes@...el.com>
Cc:	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

Sorry for bothering if you received this message twice.  I have some
issue with my mailing system.

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);

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);

Best Regards,
Huang Ying
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