nvme-pci: add trouble shooting steps for timeouts

Many users have encountered IO timeouts with a CSTS value of 0xffffffff,
which indicates a failure to read the register. While there are various
potential causes for this observation, faulty NVMe APST has been the
culprit quite frequently. Add the recommended troubleshooting steps in
the error output when this condition occurs.

Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 96579d48002a14cd82d90e16202392302cbde5aa..be053d943731baf091d2a5c7424296daf65207a1 100644 (file)
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1334,6 +1334,14 @@ static void nvme_warn_reset(struct nvme_dev *dev, u32 csts)
                dev_warn(dev->ctrl.device,
                         "controller is down; will reset: CSTS=0x%x, PCI_STATUS read failed (%d)\n",
                         csts, result);
+
+       if (csts != ~0)
+               return;
+
+       dev_warn(dev->ctrl.device,
+                "Does your device have a faulty power saving mode enabled?\n");
+       dev_warn(dev->ctrl.device,
+                "Try \"nvme_core.default_ps_max_latency_us=0 pcie_aspm=off\" and report a bug\n");
 }
 
 static enum blk_eh_timer_return nvme_timeout(struct request *req, bool reserved)