[PATCH] nvme: avoid bogus CRTO values

[Keith Busch]

From: Keith Busch <kbusch at kernel.org>

Some devices are reporting controller ready mode support, but return 0
for CRTO. These devices require a much higher time to ready than that,
so they are failing to initialize after the driver starter preferring
that value over CAP.TO.

The spec requires that CAP.TO match the appropritate CRTO value, or be
set to 0xff if CRTO is larger than that. This means that CAP.TO can be
used to validate if CRTO is reliable, and provides an appropriate
fallback for setting the timeout value if not. Use whichever is larger.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=217863
Reported-by: Cláudio Sampaio <patola at gmail.com>
Reported-by: Felix Yan <felixonmars at archlinux.org>
Based-on-a-patch-by: Felix Yan <felixonmars at archlinux.org>
Cc: stable at vger.kernel.org
Signed-off-by: Keith Busch <kbusch at kernel.org>
---
 drivers/nvme/host/core.c | 48 ++++++++++++++++++++++++----------------
 1 file changed, 29 insertions(+), 19 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 37b6fa7466620..4adc0b2f12f1e 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2245,25 +2245,8 @@ int nvme_enable_ctrl(struct nvme_ctrl *ctrl)
 	else
 		ctrl->ctrl_config = NVME_CC_CSS_NVM;
 
-	if (ctrl->cap & NVME_CAP_CRMS_CRWMS) {
-		u32 crto;
-
-		ret = ctrl->ops->reg_read32(ctrl, NVME_REG_CRTO, &crto);
-		if (ret) {
-			dev_err(ctrl->device, "Reading CRTO failed (%d)\n",
-				ret);
-			return ret;
-		}
-
-		if (ctrl->cap & NVME_CAP_CRMS_CRIMS) {
-			ctrl->ctrl_config |= NVME_CC_CRIME;
-			timeout = NVME_CRTO_CRIMT(crto);
-		} else {
-			timeout = NVME_CRTO_CRWMT(crto);
-		}
-	} else {
-		timeout = NVME_CAP_TIMEOUT(ctrl->cap);
-	}
+	if (ctrl->cap & NVME_CAP_CRMS_CRWMS && ctrl->cap & NVME_CAP_CRMS_CRIMS)
+		ctrl->ctrl_config |= NVME_CC_CRIME;
 
 	ctrl->ctrl_config |= (NVME_CTRL_PAGE_SHIFT - 12) << NVME_CC_MPS_SHIFT;
 	ctrl->ctrl_config |= NVME_CC_AMS_RR | NVME_CC_SHN_NONE;
@@ -2277,6 +2260,33 @@ int nvme_enable_ctrl(struct nvme_ctrl *ctrl)
 	if (ret)
 		return ret;
 
+	/* CAP value may change after initial CC write */
+	ret = ctrl->ops->reg_read64(ctrl, NVME_REG_CAP, &ctrl->cap);
+	if (ret)
+		return ret;
+
+	timeout = NVME_CAP_TIMEOUT(ctrl->cap);
+	if (ctrl->cap & NVME_CAP_CRMS_CRWMS) {
+		u32 crto;
+
+		ret = ctrl->ops->reg_read32(ctrl, NVME_REG_CRTO, &crto);
+		if (ret) {
+			dev_err(ctrl->device, "Reading CRTO failed (%d)\n",
+				ret);
+			return ret;
+		}
+
+		/*
+		 * CRTO should always be greater or equal to CAP.TO, but some
+		 * devices are known to get this wrong. Use the larger of the
+		 * two values.
+		 */
+		if (ctrl->ctrl_config & NVME_CC_CRIME)
+			timeout = max(timeout, NVME_CRTO_CRIMT(crto));
+		else
+			timeout = max(timeout, NVME_CRTO_CRWMT(crto));
+	}
+
 	ctrl->ctrl_config |= NVME_CC_ENABLE;
 	ret = ctrl->ops->reg_write32(ctrl, NVME_REG_CC, ctrl->ctrl_config);
 	if (ret)
-- 
2.34.1