nvme-pci: Save PCI state before putting drive into deepest state

The action of saving the PCI state will cause numerous PCI configuration
space reads which depending upon the vendor implementation may cause
the drive to exit the deepest NVMe state.

In these cases ASPM will typically resolve the PCIe link state and APST
may resolve the NVMe power state.  However it has also been observed
that this register access after quiesced will cause PC10 failure
on some device combinations.

To resolve this, move the PCI state saving to before SetFeatures has been
called.  This has been proven to resolve the issue across a 5000 sample
test on previously failing disk/system combinations.

Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>

1 files changed, 10 insertions, 7 deletions

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 6b4d7b064b38..d3f63f0c212a 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2944,11 +2944,21 @@ static int nvme_suspend(struct device *dev)
 	if (ret < 0)
 		goto unfreeze;
 
+	/*
+	 * A saved state prevents pci pm from generically controlling the
+	 * device's power. If we're using protocol specific settings, we don't
+	 * want pci interfering.
+	 */
+	pci_save_state(pdev);
+
 	ret = nvme_set_power_state(ctrl, ctrl->npss);
 	if (ret < 0)
 		goto unfreeze;
 
 	if (ret) {
+		/* discard the saved state */
+		pci_load_saved_state(pdev, NULL);
+
 		/*
 		 * Clearing npss forces a controller reset on resume. The
 		 * correct value will be resdicovered then.
@@ -2956,14 +2966,7 @@ static int nvme_suspend(struct device *dev)
 		nvme_dev_disable(ndev, true);
 		ctrl->npss = 0;
 		ret = 0;
-		goto unfreeze;
 	}
-	/*
-	 * A saved state prevents pci pm from generically controlling the
-	 * device's power. If we're using protocol specific settings, we don't
-	 * want pci interfering.
-	 */
-	pci_save_state(pdev);
 unfreeze:
 	nvme_unfreeze(ctrl);
 	return ret;