[PATCH 1/2] nvme/quirk: Add a delay before checking for adapter readiness

[Mauricio Faria de Oliveira]

From: "Guilherme G. Piccoli" <gpiccoli at linux.vnet.ibm.com>

When disabling the controller, the specification says the register
NVME_REG_CC should be written and then driver needs to wait the
adapter to be ready, which is checked by reading another register
bit (NVME_CSTS_RDY). There's a timeout validation in this checking,
so in case this timeout is reached the driver gives up and removes
the adapter from the system.

After a firmware activation procedure, the PCI_DEVICE(0x1c58, 0x0003)
(HGST adapter) end up being removed if we issue a reset_controller,
because driver keeps verifying the NVME_REG_CSTS until the timeout is
reached. This patch adds a necessary quirk for this adapter, by
introducing a delay before nvme_wait_ready(), so the reset procedure
is able to be completed. This quirk is needed because just increasing
the timeout is not enough in case of this adapter - the driver must
wait before start reading NVME_REG_CSTS register on this specific
device.

Signed-off-by: Guilherme G. Piccoli <gpiccoli at linux.vnet.ibm.com>
Reviewed-by: Christoph Hellwig <hch at lst.de>
Signed-off-by: Jens Axboe <axboe at fb.com>
[mauricfo: backport to v4.4.70 without nvme quirk handling & nvme_ctrl]
Signed-off-by: Mauricio Faria de Oliveira <mauricfo at linux.vnet.ibm.com>
Tested-by: Narasimhan Vaidyanathan <vnarasimhan at in.ibm.com>
---
 drivers/nvme/host/nvme.h |  7 +++++++
 drivers/nvme/host/pci.c  | 10 ++++++++++
 2 files changed, 17 insertions(+)

diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 044253dca30a..b8a5a8e8f57d 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -27,6 +27,13 @@ enum {
 	NVME_NS_LIGHTNVM	= 1,
 };
 
+/* The below value is the specific amount of delay needed before checking
+ * readiness in case of the PCI_DEVICE(0x1c58, 0x0003), which needs the
+ * NVME_QUIRK_DELAY_BEFORE_CHK_RDY quirk enabled. The value (in ms) was
+ * found empirically.
+ */
+#define NVME_QUIRK_DELAY_AMOUNT		2000
+
 /*
  * Represents an NVM Express device.  Each nvme_dev is a PCI function.
  */
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index c851bc53831c..e9750a0a6f2c 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1633,10 +1633,20 @@ static int nvme_wait_ready(struct nvme_dev *dev, u64 cap, bool enabled)
  */
 static int nvme_disable_ctrl(struct nvme_dev *dev, u64 cap)
 {
+	struct pci_dev *pdev = to_pci_dev(dev->dev);
+
 	dev->ctrl_config &= ~NVME_CC_SHN_MASK;
 	dev->ctrl_config &= ~NVME_CC_ENABLE;
 	writel(dev->ctrl_config, &dev->bar->cc);
 
+	/* Checking for dev->tagset is a trick to avoid sleeping on module
+	 * load, since we only need the quirk on reset_controller. Notice
+	 * that the HGST device needs this delay only in firmware activation
+	 * procedure; unfortunately we have no (easy) way to verify this.
+	 */
+	if (pdev->vendor == 0x1c58 && pdev->device == 0x0003 && dev->tagset)
+		msleep(NVME_QUIRK_DELAY_AMOUNT);
+
 	return nvme_wait_ready(dev, cap, false);
 }
 
-- 
1.8.3.1