Re: [PATCH 1/7] PCI/PM: Always return devices to D0 when thawing

Rafael J. Wysocki
2019-10-15T17:15:52Z

On Tuesday, October 15, 2019 1:00:10 AM CEST Bjorn Helgaas wrote:
> From: Dexuan Cui <decui@microsoft.com>
>
> pci_pm_thaw_noirq() is supposed to return the device to D0 and restore its
> configuration registers, but previously it only did that for devices whose
> drivers implemented the new power management ops.
>
> Hibernation, e.g., via "echo disk > /sys/power/state", involves freezing
> devices, creating a hibernation image, thawing devices, writing the image,
> and powering off. The fact that thawing did not return devices with legacy
> power management to D0 caused errors, e.g., in this path:
>
> pci_pm_thaw_noirq
> if (pci_has_legacy_pm_support(pci_dev)) # true for Mellanox VF driver
> return pci_legacy_resume_early(dev) # ... legacy PM skips the rest
> pci_set_power_state(pci_dev, PCI_D0)
> pci_restore_state(pci_dev)
> pci_pm_thaw
> if (pci_has_legacy_pm_support(pci_dev))
> pci_legacy_resume
> drv->resume
> mlx4_resume
> ...
> pci_enable_msix_range
> ...
> if (dev->current_state != PCI_D0) # <---
> return -EINVAL;
>
> which caused these warnings:
>
> mlx4_core a6d1:00:02.0: INTx is not supported in multi-function mode, aborting
> PM: dpm_run_callback(): pci_pm_thaw+0x0/0xd7 returns -95
> PM: Device a6d1:00:02.0 failed to thaw: error -95
>
> Return devices to D0 and restore config registers for all devices, not just
> those whose drivers support new power management.
>
> [bhelgaas: also call pci_restore_state() before pci_legacy_resume_early(),
> update comment, add stable tag, commit log]
> Link: https://lore.kernel.org/r/KU1P153MB016637CAEAD346F0AA8E3801BFAD0@KU1P153MB0166.APCP153.PROD.OUTLOOK.COM
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> Cc: stable@vger.kernel.org # v4.13+

No issues found, so

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

> ---
> drivers/pci/pci-driver.c | 17 +++++++++++------
> 1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index a8124e47bf6e..d4ac8ce8c1f9 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -1076,17 +1076,22 @@ static int pci_pm_thaw_noirq(struct device *dev)
> return error;
> }
>
> - if (pci_has_legacy_pm_support(pci_dev))
> - return pci_legacy_resume_early(dev);
> -
> /*
> - * 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.
> + * Both the legacy ->resume_early() and the new pm->thaw_noirq()
> + * callbacks assume the device has been returned to D0 and its
> + * config state has been restored.
> + *
> + * In addition, pci_restore_state() restores MSI-X state in MMIO
> + * space, which requires the device to be in D0, so return it to D0
> + * in case the driver's "freeze" callbacks put it into a low-power
> + * state.
> */
> pci_set_power_state(pci_dev, PCI_D0);
> pci_restore_state(pci_dev);
>
> + if (pci_has_legacy_pm_support(pci_dev))
> + return pci_legacy_resume_early(dev);
> +
> if (drv && drv->pm && drv->pm->thaw_noirq)
> error = drv->pm->thaw_noirq(dev);
>
>