On Wednesday, July 16, 2014 01:36:37 PM Bjorn Helgaas wrote:
> On Wed, Jul 16, 2014 at 03:33:42PM +0530, Vidya Sagar wrote:
> > From: Vidya Sagar <sagar.tv@xxxxxxxxx>
> >
> > Commit 1a680b7c3258 ("PCI: PCIe links may not get configured for ASPM
> > under POWERSAVE mode") 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 db288c9c5f9d ("PCI / PM: restore the original
> > behavior of pci_set_power_state()"), 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 configuring links for ASPM in do_pci_enable_device() instead of
> > pci_set_power_state()
> >
> > Suggested-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> > Signed-off-by: Vidya Sagar <sagar.tv@xxxxxxxxx>
>
> I applied this to pci/misc for v3.17 with the following changelog:
>
> It would still make me feel better if Matthew and/or Rafael acked this.
>
> PCI: Configure ASPM when enabling device
>
> We can't do ASPM configuration at enumeration-time because enabling it
> makes some defective hardware unresponsive, even if ASPM is disabled later
> (see 41cd766b0659 ("PCI: Don't enable aspm before drivers have had a chance
> to veto it"). Therefore, we have to do it after a driver claims the
> device.
>
> We previously configured ASPM in pci_set_power_state(), but that's not a
> very good place because it's not really related to setting the PCI device
> power state, and doing it there means:
>
> - We incorrectly skipped ASPM config when setting a device that's
> already in D0 to D0.
>
> - We unnecessarily configured ASPM when setting a device to a low-power
> state (the ASPM feature only applies when the device is in D0).
>
> - We unnecessarily configured ASPM when called from a .resume() method
> (ASPM configuration needs to be restored during resume, but I think
> pci_restore_pcie_state() should already do this).
>
> Move ASPM configuration from pci_set_power_state() to
> do_pci_enable_device() so we do it when a driver enables a device.
>
> [bhelgaas: changelog]
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=79621
>
> It would still make me feel better if Matthew and/or Rafael chimed in to
> make sure this is sane.
I like the change, but I'm not sure whether or not it will work for everyone.
The only way to verify that seems to be to apply it, however.
Rafael
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