[PATCH v4 3/3] PCI: Intel DC P3700 NVMe delay after FLR quirk

[Alex Williamson]

Add a device specific reset for Intel DC P3700 NVMe device which
exhibits a timeout failure in drivers waiting for the ready status to
update after NVMe enable if the driver interacts with the device too
quickly after FLR.  As this has been observed in device assignment
scenarios, resolve this with a device specific reset quirk to add an
additional, heuristically determined, delay after the FLR completes.

Link: https://bugzilla.redhat.com/show_bug.cgi?id=1592654
Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
---
 drivers/pci/quirks.c |   22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 0a4d802cb307..93791bd31a55 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -3751,6 +3751,27 @@ static int nvme_disable_and_flr(struct pci_dev *dev, int probe)
 	return 0;
 }
 
+/*
+ * Intel DC P3700 NVMe controller will timeout waiting for ready status
+ * to change after NVMe enable if the driver starts interacting with the
+ * device too quickly after FLR.  A 250ms delay after FLR has heuristically
+ * proven to produce reliably working results for device assignment cases.
+ */
+static int delay_250ms_after_flr(struct pci_dev *dev, int probe)
+{
+	if (!pcie_has_flr(dev))
+		return -ENOTTY;
+
+	if (probe)
+		return 0;
+
+	pcie_flr(dev);
+
+	msleep(250);
+
+	return 0;
+}
+
 static const struct pci_dev_reset_methods pci_dev_reset_methods[] = {
 	{ PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82599_SFP_VF,
 		 reset_intel_82599_sfp_virtfn },
@@ -3759,6 +3780,7 @@ static const struct pci_dev_reset_methods pci_dev_reset_methods[] = {
 	{ PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_IVB_M2_VGA,
 		reset_ivb_igd },
 	{ PCI_VENDOR_ID_SAMSUNG, 0xa804, nvme_disable_and_flr },
+	{ PCI_VENDOR_ID_INTEL, 0x0953, delay_250ms_after_flr },
 	{ PCI_VENDOR_ID_CHELSIO, PCI_ANY_ID,
 		reset_chelsio_generic_dev },
 	{ 0 }