[PATCH] nvme/host/core: Allow overriding of wait_ready timeout

[Balbir Singh <sblbir@amzn.com>]

Largely for debugging purposes where controllers with large
timeouts get stuck during reset. In my case I have a simple
mirroring raid configuration on top of nvme using mdadm.
If one of the controller has IO timeouts and takes very long
(128 seconds worst case) during IO, I am happy to
use this debug option to drop that controller quickly and
let the system run.

Signed-off-by: Balbir Singh <sblbir@amzn.com>
---

Changelog:
 Implement simplifications suggested in the review

NOTE:

I am still sending this out for larger review because I think
this is helpful, there is some concern that the values might
be mis-used, a quirk does not meet my requirments and the
value of the timeout is global (as in it applies to all
controllers). I think it is still useful to have this for
my use case for the lack of a better solution

 drivers/nvme/host/core.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 6ad1f1df9e44..798edc609d6a 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -40,6 +40,10 @@ module_param_named(io_timeout, nvme_io_timeout, uint, 0644);
 MODULE_PARM_DESC(io_timeout, "timeout in seconds for I/O");
 EXPORT_SYMBOL_GPL(nvme_io_timeout);
 
+static unsigned int nvme_wait_ready_timeout = 0;
+module_param_named(wait_ready_timeout, nvme_wait_ready_timeout, uint, 0644);
+MODULE_PARM_DESC(wait_ready_timeout, "timeout in seconds for ready on reset");
+
 static unsigned char shutdown_timeout = 5;
 module_param(shutdown_timeout, byte, 0644);
 MODULE_PARM_DESC(shutdown_timeout, "timeout in seconds for controller shutdown");
@@ -1930,11 +1934,15 @@ const struct block_device_operations nvme_ns_head_ops = {
 
 static int nvme_wait_ready(struct nvme_ctrl *ctrl, u64 cap, bool enabled)
 {
-	unsigned long timeout =
-		((NVME_CAP_TIMEOUT(cap) + 1) * HZ / 2) + jiffies;
+	unsigned long timeout;
 	u32 csts, bit = enabled ? NVME_CSTS_RDY : 0;
 	int ret;
 
+	if (unlikely(nvme_wait_ready_timeout))
+		timeout = (nvme_wait_ready_timeout * HZ) + jiffies;
+	else
+		timeout = ((NVME_CAP_TIMEOUT(cap) + 1) * HZ / 2) + jiffies;
+
 	while ((ret = ctrl->ops->reg_read32(ctrl, NVME_REG_CSTS, &csts)) == 0) {
 		if (csts == ~0)
 			return -ENODEV;
-- 
2.16.5


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