nvme: explicitly disable APST on quirked devices

A user reports APST is enabled, even when the NVMe is quirked or with
option "default_ps_max_latency_us=0".

The current logic will not set APST if the device is quirked. But the
NVMe in question will enable APST automatically.

Separate the logic "apst is supported" and "to enable apst", so we can
use the latter one to explicitly disable APST at initialiaztion.

BugLink: https://bugs.launchpad.net/bugs/1699004
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/nvme/host/core.c

@@ -1549,7 +1549,7 @@ static void nvme_configure_apst(struct nvme_ctrl *ctrl)
 	if (!table)
 		return;
 
-	if (ctrl->ps_max_latency_us == 0) {
+	if (!ctrl->apst_enabled || ctrl->ps_max_latency_us == 0) {
 		/* Turn off APST. */
 		apste = 0;
 		dev_dbg(ctrl->device, "APST disabled\n");
@@ -1716,7 +1716,7 @@ int nvme_init_identify(struct nvme_ctrl *ctrl)
 	u64 cap;
 	int ret, page_shift;
 	u32 max_hw_sectors;
-	u8 prev_apsta;
+	bool prev_apst_enabled;
 
 	ret = ctrl->ops->reg_read32(ctrl, NVME_REG_VS, &ctrl->vs);
 	if (ret) {
@@ -1784,16 +1784,17 @@ int nvme_init_identify(struct nvme_ctrl *ctrl)
 	ctrl->kas = le16_to_cpu(id->kas);
 
 	ctrl->npss = id->npss;
-	prev_apsta = ctrl->apsta;
+	ctrl->apsta = id->apsta;
+	prev_apst_enabled = ctrl->apst_enabled;
 	if (ctrl->quirks & NVME_QUIRK_NO_APST) {
 		if (force_apst && id->apsta) {
 			dev_warn(ctrl->device, "forcibly allowing APST due to nvme_core.force_apst -- use at your own risk\n");
-			ctrl->apsta = 1;
+			ctrl->apst_enabled = true;
 		} else {
-			ctrl->apsta = 0;
+			ctrl->apst_enabled = false;
 		}
 	} else {
-		ctrl->apsta = id->apsta;
+		ctrl->apst_enabled = id->apsta;
 	}
 	memcpy(ctrl->psd, id->psd, sizeof(ctrl->psd));
 
@@ -1823,9 +1824,9 @@ int nvme_init_identify(struct nvme_ctrl *ctrl)
 
 	kfree(id);
 
-	if (ctrl->apsta && !prev_apsta)
+	if (ctrl->apst_enabled && !prev_apst_enabled)
 		dev_pm_qos_expose_latency_tolerance(ctrl->device);
-	else if (!ctrl->apsta && prev_apsta)
+	else if (!ctrl->apst_enabled && prev_apst_enabled)
 		dev_pm_qos_hide_latency_tolerance(ctrl->device);
 
 	nvme_configure_apst(ctrl);

drivers/nvme/host/nvme.h

@@ -167,6 +167,7 @@ struct nvme_ctrl {
 
 	/* Power saving configuration */
 	u64 ps_max_latency_us;
+	bool apst_enabled;
 
 	u32 hmpre;
 	u32 hmmin;