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

Bjorn Helgaas
2019-10-14T23:01:49Z

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+
---
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);

--
2.23.0.700.g56cf767bdb-goog