[PATCH 3/3] nvme: Expose link rate switching tunables via sysfs
Liao Xuan
liaoxuan at open-hieco.net
Wed Sep 23 23:15:13 PDT 2026
Add a speed attribute group under /sys/class/nvme/nvmeX/ that
exposes the adaptive link rate switching parameters for runtime tuning:
enable - toggle the feature on/off (0/1)
monitor_interval - I/O monitoring window in milliseconds (>= 100)
min_speed - minimum PCIe generation to downgrade to (1-5)
up_threshold - windows above the threshold needed to upgrade
down_threshold - windows below the threshold needed to downgrade
The attributes are read/write and are removed when the controller is
torn down.
Signed-off-by: Liao Xuan <liaoxuan at open-hieco.net>
---
drivers/nvme/host/nvme.h | 3 +
drivers/nvme/host/speed_switch.c | 15 +++-
drivers/nvme/host/sysfs.c | 143 +++++++++++++++++++++++++++++++
3 files changed, 160 insertions(+), 1 deletion(-)
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 5d5034601..fb958ff13 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -1076,6 +1076,9 @@ extern const struct attribute_group nvme_dev_attrs_group;
extern const struct attribute_group nvme_dev_diag_attrs_group;
extern const struct attribute_group *nvme_subsys_attrs_groups[];
extern const struct attribute_group *nvme_dev_attr_groups[];
+#ifdef CONFIG_NVME_SPEED_SWITCH
+extern const struct attribute_group nvme_speed_attr_group;
+#endif
extern const struct block_device_operations nvme_bdev_ops;
void nvme_delete_ctrl_sync(struct nvme_ctrl *ctrl);
diff --git a/drivers/nvme/host/speed_switch.c b/drivers/nvme/host/speed_switch.c
index 22f180c81..fce426845 100644
--- a/drivers/nvme/host/speed_switch.c
+++ b/drivers/nvme/host/speed_switch.c
@@ -325,7 +325,7 @@ void nvme_speed_switch_init(struct nvme_ctrl *ctrl)
{
struct nvme_speed_switch *sw = &ctrl->speed_switch;
struct pci_dev *pdev;
- int max_speed;
+ int max_speed, ret;
if (boot_cpu_data.x86_vendor != X86_VENDOR_HYGON) {
dev_dbg(ctrl->device,
@@ -376,6 +376,18 @@ void nvme_speed_switch_init(struct nvme_ctrl *ctrl)
timer_setup(&sw->timer, nvme_speed_switch_timer_fn, 0);
atomic_set(&sw->timer_active, NVME_SPEED_TIMER_INACTIVE);
WRITE_ONCE(sw->enabled, true);
+
+ ret = sysfs_create_group(&ctrl->device->kobj, &nvme_speed_attr_group);
+ if (ret) {
+ dev_err(ctrl->device,
+ "failed to create link rate switching sysfs group (%d)\n",
+ ret);
+ timer_delete_sync(&sw->timer);
+ free_percpu(sw->stats);
+ sw->stats = NULL;
+ WRITE_ONCE(sw->enabled, false);
+ return;
+ }
sw->initialized = true;
dev_info(ctrl->device,
@@ -405,6 +417,7 @@ void nvme_speed_switch_exit(struct nvme_ctrl *ctrl)
WRITE_ONCE(sw->enabled, false);
timer_delete_sync(&sw->timer);
cancel_work_sync(&sw->work);
+ sysfs_remove_group(&ctrl->device->kobj, &nvme_speed_attr_group);
free_percpu(sw->stats);
sw->stats = NULL;
diff --git a/drivers/nvme/host/sysfs.c b/drivers/nvme/host/sysfs.c
index 75b2d69b5..cd899b87b 100644
--- a/drivers/nvme/host/sysfs.c
+++ b/drivers/nvme/host/sysfs.c
@@ -1308,3 +1308,146 @@ const struct attribute_group *nvme_subsys_attrs_groups[] = {
&nvme_subsys_attrs_group,
NULL,
};
+
+#ifdef CONFIG_NVME_SPEED_SWITCH
+enum nvme_speed_attr_id {
+ NVME_SPEED_ATTR_ENABLE,
+ NVME_SPEED_ATTR_MONITOR_INTERVAL,
+ NVME_SPEED_ATTR_MIN_SPEED,
+ NVME_SPEED_ATTR_UP_THRESHOLD,
+ NVME_SPEED_ATTR_DOWN_THRESHOLD,
+};
+
+struct nvme_speed_attr {
+ struct device_attribute attr;
+ enum nvme_speed_attr_id id;
+};
+
+static ssize_t nvme_speed_attr_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct nvme_ctrl *ctrl = dev_get_drvdata(dev);
+ struct nvme_speed_switch *sw = &ctrl->speed_switch;
+ struct nvme_speed_attr *sa =
+ container_of(attr, struct nvme_speed_attr, attr);
+ u32 val;
+
+ switch (sa->id) {
+ case NVME_SPEED_ATTR_ENABLE:
+ val = READ_ONCE(sw->enabled);
+ break;
+ case NVME_SPEED_ATTR_MONITOR_INTERVAL:
+ val = READ_ONCE(sw->monitor_interval);
+ break;
+ case NVME_SPEED_ATTR_MIN_SPEED:
+ val = READ_ONCE(sw->min_speed);
+ break;
+ case NVME_SPEED_ATTR_UP_THRESHOLD:
+ val = READ_ONCE(sw->up_threshold);
+ break;
+ case NVME_SPEED_ATTR_DOWN_THRESHOLD:
+ val = READ_ONCE(sw->down_threshold);
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return sysfs_emit(buf, "%u\n", val);
+}
+
+static ssize_t nvme_speed_attr_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct nvme_ctrl *ctrl = dev_get_drvdata(dev);
+ struct nvme_speed_switch *sw = &ctrl->speed_switch;
+ struct nvme_speed_attr *sa =
+ container_of(attr, struct nvme_speed_attr, attr);
+ u32 val;
+ int ret;
+
+ ret = kstrtou32(buf, 10, &val);
+ if (ret)
+ return ret;
+
+ switch (sa->id) {
+ case NVME_SPEED_ATTR_ENABLE:
+ if (val > 1)
+ return -EINVAL;
+ if (!val && READ_ONCE(sw->enabled)) {
+ WRITE_ONCE(sw->enabled, false);
+ timer_delete_sync(&sw->timer);
+ cancel_work_sync(&sw->work);
+ atomic_set(&sw->timer_active, NVME_SPEED_TIMER_INACTIVE);
+ } else
+ WRITE_ONCE(sw->enabled, val);
+ break;
+ case NVME_SPEED_ATTR_MONITOR_INTERVAL:
+ if (val < 100)
+ return -EINVAL;
+ WRITE_ONCE(sw->monitor_interval, val);
+ break;
+ case NVME_SPEED_ATTR_MIN_SPEED:
+ if (val < 1 || val > 5)
+ return -EINVAL;
+ if (val > sw->max_speed)
+ val = sw->max_speed;
+ WRITE_ONCE(sw->min_speed, val);
+ break;
+ case NVME_SPEED_ATTR_UP_THRESHOLD:
+ WRITE_ONCE(sw->up_threshold, val);
+ break;
+ case NVME_SPEED_ATTR_DOWN_THRESHOLD:
+ WRITE_ONCE(sw->down_threshold, val);
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return count;
+}
+
+static struct nvme_speed_attr nvme_speed_attr_enable = {
+ .attr = __ATTR(enable, 0644,
+ nvme_speed_attr_show, nvme_speed_attr_store),
+ .id = NVME_SPEED_ATTR_ENABLE,
+};
+
+static struct nvme_speed_attr nvme_speed_attr_monitor_interval = {
+ .attr = __ATTR(monitor_interval, 0644,
+ nvme_speed_attr_show, nvme_speed_attr_store),
+ .id = NVME_SPEED_ATTR_MONITOR_INTERVAL,
+};
+
+static struct nvme_speed_attr nvme_speed_attr_min_speed = {
+ .attr = __ATTR(min_speed, 0644,
+ nvme_speed_attr_show, nvme_speed_attr_store),
+ .id = NVME_SPEED_ATTR_MIN_SPEED,
+};
+
+static struct nvme_speed_attr nvme_speed_attr_up_threshold = {
+ .attr = __ATTR(up_threshold, 0644,
+ nvme_speed_attr_show, nvme_speed_attr_store),
+ .id = NVME_SPEED_ATTR_UP_THRESHOLD,
+};
+
+static struct nvme_speed_attr nvme_speed_attr_down_threshold = {
+ .attr = __ATTR(down_threshold, 0644,
+ nvme_speed_attr_show, nvme_speed_attr_store),
+ .id = NVME_SPEED_ATTR_DOWN_THRESHOLD,
+};
+
+static struct attribute *nvme_speed_attrs[] = {
+ &nvme_speed_attr_enable.attr.attr,
+ &nvme_speed_attr_monitor_interval.attr.attr,
+ &nvme_speed_attr_min_speed.attr.attr,
+ &nvme_speed_attr_up_threshold.attr.attr,
+ &nvme_speed_attr_down_threshold.attr.attr,
+ NULL,
+};
+
+const struct attribute_group nvme_speed_attr_group = {
+ .name = "speed",
+ .attrs = nvme_speed_attrs,
+};
+#endif /* CONFIG_NVME_SPEED_SWITCH */
--
2.43.0
More information about the Linux-nvme
mailing list