[PATCH v3] nvme/pci: Log PCI_STATUS when the controller dies

[Andy Lutomirski]

When debugging nvme controller crashes, it's nice to know whether
the controller died cleanly so that the failure is just reflected in
CSTS, it died and put an error in PCI_STATUS, or whether it died so
badly that it stopped responding to PCI configuration space reads.

I've seen a failure that gives 0xffff in PCI_STATUS on a Samsung
"SM951 NVMe SAMSUNG 256GB" with firmware "BXW75D0Q".

Reviewed-by: Christoph Hellwig <hch at lst.de>
Signed-off-by: Andy Lutomirski <luto at kernel.org>
---
 drivers/nvme/host/pci.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 5e52034ab010..628dc916ae9a 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1281,6 +1281,24 @@ static bool nvme_should_reset(struct nvme_dev *dev, u32 csts)
 	return true;
 }
 
+static void nvme_warn_reset(struct nvme_dev *dev, u32 csts)
+{
+	/* Read a config register to help see what died. */
+	u16 pci_status;
+	int result;
+
+	result = pci_read_config_word(to_pci_dev(dev->dev), PCI_STATUS,
+				      &pci_status);
+	if (result == PCIBIOS_SUCCESSFUL)
+		dev_warn(dev->dev,
+			 "controller is down; will reset: CSTS=0x%x, PCI_STATUS=0x%hx\n",
+			 csts, pci_status);
+	else
+		dev_warn(dev->dev,
+			 "controller is down; will reset: CSTS=0x%x, PCI_STATUS read failed (%d)\n",
+			 csts, result);
+}
+
 static void nvme_watchdog_timer(unsigned long data)
 {
 	struct nvme_dev *dev = (struct nvme_dev *)data;
@@ -1289,9 +1307,7 @@ static void nvme_watchdog_timer(unsigned long data)
 	/* Skip controllers under certain specific conditions. */
 	if (nvme_should_reset(dev, csts)) {
 		if (!nvme_reset(dev))
-			dev_warn(dev->dev,
-				"Failed status: 0x%x, reset controller.\n",
-				csts);
+			 nvme_warn_reset(dev, csts);
 		return;
 	}
 
-- 
2.9.3