[PATCH 1/3] [SRU Y/Z/A] nvme: Display raw APST configuration via DYNAMIC_DEBUG

[Kai-Heng Feng]

From: Andy Lutomirski <luto at kernel.org>

BugLink: https://bugs.launchpad.net/bugs/1699004

Debugging APST is currently a bit of a pain.  This gives optional
simple log messages that describe the APST state.

The easiest way to use this is probably with the nvme_core.dyndbg=+p
module parameter.

Signed-off-by: Andy Lutomirski <luto at kernel.org>
Reviewed-by: Christoph Hellwig <hch at lst.de>
Signed-off-by: Jens Axboe <axboe at fb.com>
(cherry picked from commit fb0dc3993b537e12ce63511d535ff86efff13c8f)
Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
---
 drivers/nvme/host/core.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 0b81bbf635a6..0acb533e5069 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1222,6 +1222,8 @@ static void nvme_configure_apst(struct nvme_ctrl *ctrl)
 
 	unsigned apste;
 	struct nvme_feat_auto_pst *table;
+	u64 max_lat_us = 0;
+	int max_ps = -1;
 	int ret;
 
 	/*
@@ -1243,6 +1245,7 @@ static void nvme_configure_apst(struct nvme_ctrl *ctrl)
 	if (ctrl->ps_max_latency_us == 0) {
 		/* Turn off APST. */
 		apste = 0;
+		dev_dbg(ctrl->device, "APST disabled\n");
 	} else {
 		__le64 target = cpu_to_le64(0);
 		int state;
@@ -1292,9 +1295,22 @@ static void nvme_configure_apst(struct nvme_ctrl *ctrl)
 
 			target = cpu_to_le64((state << 3) |
 					     (transition_ms << 8));
+
+			if (max_ps == -1)
+				max_ps = state;
+
+			if (total_latency_us > max_lat_us)
+				max_lat_us = total_latency_us;
 		}
 
 		apste = 1;
+
+		if (max_ps == -1) {
+			dev_dbg(ctrl->device, "APST enabled but no non-operational states are available\n");
+		} else {
+			dev_dbg(ctrl->device, "APST enabled: max PS = %d, max round-trip latency = %lluus, table = %*phN\n",
+				max_ps, max_lat_us, (int)sizeof(*table), table);
+		}
 	}
 
 	ret = nvme_set_features(ctrl, NVME_FEAT_AUTO_PST, apste,
-- 
2.13.2