@@ -26,6 +26,7 @@
#include <linux/ptrace.h>
#include <linux/nvme_ioctl.h>
#include <linux/t10-pi.h>
+#include <linux/pm_qos.h>
#include <scsi/sg.h>
#include <asm/unaligned.h>
@@ -39,6 +40,11 @@ module_param(nvme_major, int, 0);
static int nvme_char_major;
module_param(nvme_char_major, int, 0);
+static unsigned long default_ps_max_latency_us = 25000;
+module_param(default_ps_max_latency_us, ulong, 0644);
+MODULE_PARM_DESC(default_ps_max_latency_us,
+ "max power saving latency for new devices; use PM QOS to change per device");
+
static LIST_HEAD(nvme_ctrl_list);
DEFINE_SPINLOCK(dev_list_lock);
@@ -879,6 +885,122 @@ static void nvme_set_queue_limits(struct nvme_ctrl *ctrl,
blk_queue_virt_boundary(q, ctrl->page_size - 1);
}
+static void nvme_configure_apst(struct nvme_ctrl *ctrl)
+{
+ /*
+ * APST (Autonomous Power State Transition) lets us program a
+ * table of power state transitions that the controller will
+ * perform automatically. We configure it with a simple
+ * heuristic: we are willing to spend at most 2% of the time
+ * transitioning between power states. Therefore, when running
+ * in any given state, we will enter the next lower-power
+ * non-operational state after waiting 100 * (enlat + exlat)
+ * microseconds, as long as that state's total latency is under
+ * the requested maximum latency.
+ *
+ * We will not autonomously enter any non-operational state for
+ * which the total latency exceeds ps_max_latency_us. Users
+ * can set ps_max_latency_us to zero to turn off APST.
+ */
+
+ unsigned apste;
+ struct nvme_feat_auto_pst *table;
+ int ret;
+
+ /*
+ * If APST isn't supported or if we haven't been initialized yet,
+ * then don't do anything.
+ */
+ if (!ctrl->apsta)
+ return;
+
+ if (ctrl->npss > 31) {
+ dev_warn(ctrl->device, "NPSS is invalid; not using APST\n");
+ return;
+ }
+
+ table = kzalloc(sizeof(*table), GFP_KERNEL);
+ if (!table)
+ return;
+
+ if (ctrl->ps_max_latency_us == 0) {
+ /* Turn off APST. */
+ apste = 0;
+ } else {
+ __le64 target = cpu_to_le64(0);
+ int state;
+
+ /*
+ * Walk through all states from lowest- to highest-power.
+ * According to the spec, lower-numbered states use more
+ * power. NPSS, despite the name, is the index of the
+ * lowest-power state, not the number of states.
+ */
+ for (state = (int)ctrl->npss; state >= 0; state--) {
+ u64 total_latency_us, transition_ms;
+
+ if (target)
+ table->entries[state] = target;
+
+ /*
+ * Is this state a useful non-operational state for
+ * higher-power states to autonomously transition to?
+ */
+ if (!(ctrl->psd[state].flags &
+ NVME_PS_FLAGS_NON_OP_STATE))
+ continue;
+
+ total_latency_us =
+ (u64)le32_to_cpu(ctrl->psd[state].entry_lat) +
+ + le32_to_cpu(ctrl->psd[state].exit_lat);
+ if (total_latency_us > ctrl->ps_max_latency_us)
+ continue;
+
+ /*
+ * This state is good. Use it as the APST idle
+ * target for higher power states.
+ */
+ transition_ms = total_latency_us + 19;
+ do_div(transition_ms, 20);
+ if (transition_ms > (1 << 24) - 1)
+ transition_ms = (1 << 24) - 1;
+
+ target = cpu_to_le64((state << 3) |
+ (transition_ms << 8));
+ }
+
+ apste = 1;
+ }
+
+ ret = nvme_set_features(ctrl, NVME_FEAT_AUTO_PST, apste,
+ table, sizeof(*table), NULL);
+ if (ret)
+ dev_err(ctrl->device, "failed to set APST feature (%d)\n", ret);
+
+ kfree(table);
+}
+
+static void nvme_set_latency_tolerance(struct device *dev, s32 val)
+{
+ struct nvme_ctrl *ctrl = dev_get_drvdata(dev);
+ u64 latency;
+
+ switch (val) {
+ case PM_QOS_LATENCY_TOLERANCE_NO_CONSTRAINT:
+ case PM_QOS_LATENCY_ANY:
+ latency = U64_MAX;
+ break;
+
+ default:
+ latency = val;
+ }
+
+ if (ctrl->ps_max_latency_us != latency) {
+ ctrl->ps_max_latency_us = latency;
+ nvme_configure_apst(ctrl);
+ }
+}
+
struct nvme_core_quirk_entry {
/*
* NVMe model and firmware strings are padded with spaces. For
@@ -892,6 +1014,16 @@ struct nvme_core_quirk_entry {
};
static const struct nvme_core_quirk_entry core_quirks[] = {
+ /*
+ * Seen on a Samsung "SM951 NVMe SAMSUNG 256GB": using APST causes
+ * the controller to go out to lunch. It dies when the watchdog
+ * timer reads CSTS and gets 0xffffffff.
+ */
+ {
+ .vid = 0x144d,
+ .fr = "BXW75D0Q",
+ .quirks = NVME_QUIRK_NO_APST,
+ },
};
/* match is null-terminated but idstr is space-padded. */
@@ -933,6 +1065,7 @@ int nvme_init_identify(struct nvme_ctrl *ctrl)
struct nvme_id_ctrl *id;
u64 cap;
int ret, page_shift;
+ u8 prev_apsta;
ret = ctrl->ops->reg_read32(ctrl, NVME_REG_VS, &ctrl->vs);
if (ret) {
@@ -1000,9 +1133,22 @@ int nvme_init_identify(struct nvme_ctrl *ctrl)
nvme_set_queue_limits(ctrl, ctrl->admin_q);
+ ctrl->npss = id->npss;
+ prev_apsta = ctrl->apsta;
+ ctrl->apsta = (ctrl->quirks & NVME_QUIRK_NO_APST) ? 0 : id->apsta;
+ memcpy(ctrl->psd, id->psd, sizeof(ctrl->psd));
+
kfree(id);
+ if (ctrl->apsta && !prev_apsta)
+ dev_pm_qos_expose_latency_tolerance(ctrl->device);
+ else if (!ctrl->apsta && prev_apsta)
+ dev_pm_qos_hide_latency_tolerance(ctrl->device);
+
+ nvme_configure_apst(ctrl);
+
ctrl->identified = true;
+
return ret;
}
@@ -1487,6 +1633,14 @@ int nvme_init_ctrl(struct nvme_ctrl *ctrl, struct device *dev,
list_add_tail(&ctrl->node, &nvme_ctrl_list);
spin_unlock(&dev_list_lock);
+ /*
+ * Initialize latency tolerance controls. The sysfs files won't
+ * be visible to userspace unless the device actually supports APST.
+ */
+ ctrl->device->power.set_latency_tolerance = nvme_set_latency_tolerance;
+ dev_pm_qos_update_user_latency_tolerance(ctrl->device,
+ min(default_ps_max_latency_us, (unsigned long)S32_MAX));
+
return 0;
out_release_instance:
nvme_release_instance(ctrl);
@@ -71,6 +71,11 @@ enum nvme_quirks {
* readiness, which is done by reading the NVME_CSTS_RDY bit.
*/
NVME_QUIRK_DELAY_BEFORE_CHK_RDY = (1 << 3),
+
+ /*
+ * APST should not be used.
+ */
+ NVME_QUIRK_NO_APST = (1 << 4),
};
/* The below value is the specific amount of delay needed before checking
@@ -108,8 +113,14 @@ struct nvme_ctrl {
u8 event_limit;
u8 vwc;
u32 vs;
+ u8 npss;
+ u8 apsta;
bool subsystem;
unsigned long quirks;
+ struct nvme_id_power_state psd[32];
+
+ /* Power saving configuration */
+ u64 ps_max_latency_us;
};
/*
@@ -528,6 +528,12 @@ struct nvme_dsm_range {
__le64 slba;
};
+/* Features */
+
+struct nvme_feat_auto_pst {
+ __le64 entries[32];
+};
+
/* Admin commands */
enum nvme_admin_opcode {