Re: [PATCH v1] PCI: enable ASPM configuration in PCIE POWERSAVE mode

From: Bjorn Helgaas
Date: Sat Jul 05 2014 - 15:02:11 EST


[+cc Rafael]

On Sat, Jul 05, 2014 at 12:57:36PM -0600, Bjorn Helgaas wrote:
> [+cc Matthew]
>
> On Tue, Jul 01, 2014 at 12:46:18PM +0530, Vidya Sagar wrote:
> > commit 1a680b7c moved pcie_aspm_powersave_config_link() out of
> > pci_raw_set_power_state() to pci_set_power_state() which would enable
> > ASPM. But, with commit db288c9c, which re-introduced the following check
> > ./drivers/pci/pci.c: pci_set_power_state()
> > + /* Check if we're already there */
> > + if (dev->current_state == state)
> > + return 0;
> > in pci_set_power_state(), call to pcie_aspm_powersave_config_link() is never
> > made leaving ASPM broken.
> > Fix it by not returning from when the above condition is true, rather, jump to
> > ASPM configuration code and exit from there eventually.
>
> Rafael, Matthew, any comments? We have vacillated on this before and
> the web is already pretty tangled.
>
> Vidya, can you give more details about the bug fixed by this change?
> What's the scenario? Are we resuming and the device is powered up but
> ASPM isn't enabled? Maybe you could collect more details in a
> http://bugzilla.kernel.org report?
>
> > Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
> > ---
> > drivers/pci/pci.c | 6 ++++--
> > 1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index 1c8592b..ded24c4 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -804,7 +804,7 @@ EXPORT_SYMBOL_GPL(__pci_complete_power_transition);
> > */
> > int pci_set_power_state(struct pci_dev *dev, pci_power_t state)
> > {
> > - int error;
> > + int error = 0;
> >
> > /* bound the state we're entering */
> > if (state > PCI_D3cold)
> > @@ -821,7 +821,7 @@ int pci_set_power_state(struct pci_dev *dev, pci_power_t state)
> >
> > /* Check if we're already there */
> > if (dev->current_state == state)
> > - return 0;
> > + goto config_aspm;
> >
> > __pci_start_power_transition(dev, state);
> >
> > @@ -839,6 +839,8 @@ int pci_set_power_state(struct pci_dev *dev, pci_power_t state)
> >
> > if (!__pci_complete_power_transition(dev, state))
> > error = 0;
> > +
> > +config_aspm:
> > /*
> > * When aspm_policy is "powersave" this call ensures
> > * that ASPM is configured.
> > --
> > 1.8.1.5
> >
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