[PATCH v2] nvme: temporary fix for Apple controller reset

[guenther@tum.de (Stephan Günther)]

Recent patches added basic support for the Apple NVMe controller but
still cause resets and data corruption on that particular controller
when a specific pattern of read/flush commands occurs. Limiting the
queue depth to 2 works around that issue.

This patch enforces that limit only for the Apple controller and is
considered a temporary fix until we find the root source of that
problem.

Signed-off-by: Stephan G?nther <guenther at tum.de>
Signed-off-by: Maurice Leclaire <leclaire at in.tum.de>
---
 drivers/nvme/host/pci.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 8187df2..d3c2b03 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2701,6 +2701,18 @@ static int nvme_dev_map(struct nvme_dev *dev)
 	dev->q_depth = min_t(int, NVME_CAP_MQES(cap) + 1, NVME_Q_DEPTH);
 	dev->db_stride = 1 << NVME_CAP_STRIDE(cap);
 	dev->dbs = ((void __iomem *)dev->bar) + 4096;
+
+	/*
+ 	 * Temporary fix for the Apple controller found in the MacBook8,1 and
+	 * some MacBook7,1 to avoid controller resets and data loss.
+ 	 */
+	if (pdev->vendor == PCI_VENDOR_ID_APPLE && pdev->device == 0x2001) {
+ 		dev->q_depth = 2;
+		dev_warn(dev->dev, "detected Apple NVMe controller, set "
+			"queue depth=%u to work around controller resets\n",
+			dev->q_depth);
+	}
+
 	if (readl(&dev->bar->vs) >= NVME_VS(1, 2))
 		dev->cmb = nvme_map_cmb(dev);