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 <l...@kernel.org>
---
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 4fc58866640e..52b4e52b85a2 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1278,6 +1278,8 @@ 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;
/*
@@ -1299,6 +1301,7 @@ 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;
@@ -1340,9 +1343,22 @@ 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,
--
2.9.3
