Patch "nvme/quirk: Add a delay before checking for adapter readiness" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

nvme/quirk: Add a delay before checking for adapter readiness

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
nvme-quirk-add-a-delay-before-checking-for-adapter-readiness.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: "Guilherme G. Piccoli" <[email protected]>
Date: Tue, 14 Jun 2016 18:22:41 -0300
Subject: nvme/quirk: Add a delay before checking for adapter readiness

From: Guilherme G. Piccoli <[email protected]>

commit 54adc01055b75ec8769c5a36574c7a0895c0c0b2 upstream.

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.

---
 drivers/nvme/host/nvme.h |    7 +++++++
 drivers/nvme/host/pci.c  |   10 ++++++++++
 2 files changed, 17 insertions(+)

@@ -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.
  */

@@ -1633,10 +1633,20 @@ static int nvme_wait_ready(struct nvme_d
  */
 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);
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/nvme-apply-delay_before_chk_rdy-quirk-at-probe-time-too.patch queue-4.4/nvme-quirk-add-a-delay-before-checking-for-adapter-readiness.patch