On Mon, Nov 04, 2019 at 06:00:00PM -0600, Bjorn Helgaas wrote:
> > > > > The outline of the pci_pm_resume_noirq() part of this patch is:
> > > > >
> > > > > pci_pm_resume_noirq
> > > > > if (!dev->skip_bus_pm ...) # <-- condition 1
> > > > > pci_pm_default_resume_early
> > > > > pci_power_up
> > > > > if (platform_pci_power_manageable()) # _PS0 or _PR0 exist?
> > > > > platform_pci_set_power_state
> > > > > pci_platform_pm->set_state
> > > > > acpi_pci_set_power_state(PCI_D0) # acpi_pci_platform_pm.set_state
> > > > > acpi_device_set_power(ACPI_STATE_D0) # <-- eval _PS0
> > > > > + if (d3cold) # <-- condition 2
> > > > > + pci_bridge_wait_for_secondary_bus
>
> > The reason why pci_bridge_wait_for_secondary_bus() is called almost the
> > last is that I figured we want to resume the root/downstream port
> > completely first before we start delaying for the device downstream.
>
> For understandability, I think the wait needs to go in some function
> that contains "PCI_D0", e.g., platform_pci_set_power_state() or
> pci_power_up(), so it's connected with the transition from D3cold to
> D0.
>
> Since pci_pm_default_resume_early() is the only caller of
> pci_power_up(), maybe we should just inline pci_power_up(), e.g.,
> something like this:
>
> static void pci_pm_default_resume_early(struct pci_dev *pci_dev)
> {
> pci_power_state_t prev_state = pci_dev->current_state;
>
> if (platform_pci_power_manageable(pci_dev))
> platform_pci_set_power_state(pci_dev, PCI_D0);
>
> pci_raw_set_power_state(pci_dev, PCI_D0);
> pci_update_current_state(pci_dev, PCI_D0);
>
> pci_restore_state(pci_dev);
> pci_pme_restore(pci_dev);
>
> if (prev_state == PCI_D3cold)
> pci_bridge_wait_for_secondary_bus(dev);
> }
OK, I'll see if this works.
> I don't understand why we call both platform_pci_set_power_state() and
> pci_raw_set_power_state().
platform_pci_set_power_state() deals with the ACPI methods such as
calling _PS0 after D3hot. To transition the device from D3hot to D0 you
need the PMCSR write which is done in pci_raw_set_power_state().
> I thought platform_pci_set_power_state()
> should put the device in D0, so we shouldn't need the PCI_PM_CTRL
> update in pci_raw_set_power_state(), although we probably do need
> things like pci_restore_bars() and pcie_aspm_pm_state_change().
>
> And in fact, it seems wrong that if platform_pci_set_power_state()
> puts the device in D0 and the device lacks a PM capability, we bail
> out of pci_raw_set_power_state() before calling pci_restore_bars().
>
> Tangent: I think "pci_pm_default_resume_early" is the wrong name for
> this because "default" suggests that this is what we fall back to if a
> driver or arch doesn't supply a more specific method. But here we're
> doing mandatory things that cannot be overridden, so I think something
> like "pci_pm_core_resume_early()" would be more accurate.
>
> > Need to call it before port services (pciehp) is resumed, though.
>
> I guess this is because pciehp_resume() looks at PCI_EXP_LNKSTA and
> will be confused if the link isn't up yet?
Yes.
> > If you think it is fine to do the delay before we have restored
> > everything I can move it inside pci_power_up() or call it after
> > pci_pm_default_resume_early() as above. I think at least we should make
> > sure all the saved registers are restored before so that the link
> > activation check actually works.
>
> What needs to be restored to make pcie_wait_for_link_delay() work?
I'm not entirely sure. I think that pci_restore_state() at least should
be called so that the PCIe capability gets restored. Maybe not event
that because Data Link Layer Layer Active always reflects the DL_Active
or not and it does not need to be enabled separately.
> And what event does the restore need to be ordered with?
Not sure I follow you here.
