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SubjectRe: [PATCH] PCI / PM: Force devices to D0 in pci_pm_thaw_noirq()
On Fri, Dec 15, 2017 at 03:07:18AM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> It is incorrect to call pci_restore_state() for devices in low-power
> states (D1-D3), as that involves the restoration of MSI setup which
> requires MMIO to be operational and that is only the case in D0.
>
> However, pci_pm_thaw_noirq() may do that if the driver's "freeze"
> callbacks put the device into a low-power state, so fix it by making
> it force devices into D0 via pci_set_power_state() instead of trying
> to "update" their power state which is pointless.
>
> Fixes: e60514bd4485 (PCI/PM: Restore the status of PCI devices across hibernation)
> Cc: 4.13+ <stable@vger.kernel.org> # 4.13+
> Reported-by: Thomas Gleixner <tglx@linutronix.de>
> Reported-by: Maarten Lankhorst <dev@mblankhorst.nl>
> Tested-by: Thomas Gleixner <tglx@linutronix.de>
> Tested-by: Maarten Lankhorst <dev@mblankhorst.nl>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Acked-by: Bjorn Helgaas <bhelgaas@google.com>

Let me know if you want me to take this. I don't have anything
currently queued up that touches pci-driver.c, so I'm happy if you
take it yourself.

> ---
>
> The bug is not as old as I thought, actually.
>
> Yes, we did the pci_update_current_state() in pci_pm_thaw_noirq()
> forever, but it started to be problematic in 4.13, when we started
> to call pci_restore_state() in addition to it to fix another issue.
>
> ---
> drivers/pci/pci-driver.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> Index: linux-pm/drivers/pci/pci-driver.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci-driver.c
> +++ linux-pm/drivers/pci/pci-driver.c
> @@ -1027,7 +1027,12 @@ static int pci_pm_thaw_noirq(struct devi
> if (pci_has_legacy_pm_support(pci_dev))
> return pci_legacy_resume_early(dev);
>
> - pci_update_current_state(pci_dev, PCI_D0);
> + /*
> + * pci_restore_state() requires the device to be in D0 (because of MSI
> + * restoration among other things), so force it into D0 in case the
> + * driver's "freeze" callbacks put it into a low-power state directly.
> + */
> + pci_set_power_state(pci_dev, PCI_D0);
> pci_restore_state(pci_dev);
>
> if (drv && drv->pm && drv->pm->thaw_noirq)
>

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