linux-kernel - [PATCH] nvme-pci: Save PCI state before putting drive into deepest state

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Date:   Wed, 11 Sep 2019 18:42:33 -0500
From:   Mario Limonciello <mario.limonciello@...l.com>
To:     Keith Busch <kbusch@...nel.org>
Cc:     Jens Axboe <axboe@...com>, Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        linux-nvme@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>,
        Ryan Hong <Ryan.Hong@...l.com>, Crag Wang <Crag.Wang@...l.com>,
        sjg@...gle.com, Jared Dominguez <jared.dominguez@...l.com>,
        Mario Limonciello <mario.limonciello@...l.com>
Subject: [PATCH] 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@...l.com>
---
 drivers/nvme/host/pci.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 732d5b6..9b3fed4 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2894,6 +2894,13 @@ 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;
@@ -2908,12 +2915,6 @@ static int nvme_suspend(struct device *dev)
 		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;
-- 
2.7.4