drm/i915/slpc: Add sysfs for SLPC power profiles

Default SLPC power profile is Base(0). Power Saving mode(1)
has conservative up/down thresholds and is suitable for use with
apps that typically need to be power efficient.

Selected power profile will be displayed in this format-

$ cat slpc_power_profile

  [base]    power_saving

$ echo power_saving > slpc_power_profile
$ cat slpc_power_profile

  base    [power_saving]

v2: Disable waitboost in power saving profile, update sysfs
format and add some kernel doc for SLPC (Rodrigo)

v3: Update doc with info about power profiles (Rodrigo)

v4: Checkpatch warning and remove extra line (Rodrigo)

Cc: Sushma Venkatesh Reddy <sushma.venkatesh.reddy@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250117215753.749906-1-vinay.belgaumkar@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/i915/gt/intel_gt_sysfs_pm.c

@@ -464,6 +464,45 @@ static ssize_t slpc_ignore_eff_freq_store(struct kobject *kobj,
 	return err ?: count;
 }
 
+static ssize_t slpc_power_profile_show(struct kobject *kobj,
+				       struct kobj_attribute *attr,
+				       char *buff)
+{
+	struct intel_gt *gt = intel_gt_sysfs_get_drvdata(kobj, attr->attr.name);
+	struct intel_guc_slpc *slpc = &gt->uc.guc.slpc;
+
+	switch (slpc->power_profile) {
+	case SLPC_POWER_PROFILES_BASE:
+		return sysfs_emit(buff, "[%s]    %s\n", "base", "power_saving");
+	case SLPC_POWER_PROFILES_POWER_SAVING:
+		return sysfs_emit(buff, "%s    [%s]\n", "base", "power_saving");
+	}
+
+	return sysfs_emit(buff, "%u\n", slpc->power_profile);
+}
+
+static ssize_t slpc_power_profile_store(struct kobject *kobj,
+					struct kobj_attribute *attr,
+					const char *buff, size_t count)
+{
+	struct intel_gt *gt = intel_gt_sysfs_get_drvdata(kobj, attr->attr.name);
+	struct intel_guc_slpc *slpc = &gt->uc.guc.slpc;
+	char power_saving[] = "power_saving";
+	char base[] = "base";
+	int err;
+	u32 val;
+
+	if (!strncmp(buff, power_saving, sizeof(power_saving) - 1))
+		val = SLPC_POWER_PROFILES_POWER_SAVING;
+	else if (!strncmp(buff, base, sizeof(base) - 1))
+		val = SLPC_POWER_PROFILES_BASE;
+	else
+		return -EINVAL;
+
+	err = intel_guc_slpc_set_power_profile(slpc, val);
+	return err ?: count;
+}
+
 struct intel_gt_bool_throttle_attr {
 	struct attribute attr;
 	ssize_t (*show)(struct kobject *kobj, struct kobj_attribute *attr,
@@ -668,6 +707,7 @@ INTEL_GT_ATTR_RO(media_RP0_freq_mhz);
 INTEL_GT_ATTR_RO(media_RPn_freq_mhz);
 
 INTEL_GT_ATTR_RW(slpc_ignore_eff_freq);
+INTEL_GT_ATTR_RW(slpc_power_profile);
 
 static const struct attribute *media_perf_power_attrs[] = {
 	&attr_media_freq_factor.attr,
@@ -864,6 +904,13 @@ void intel_gt_sysfs_pm_init(struct intel_gt *gt, struct kobject *kobj)
 			gt_warn(gt, "failed to create ignore_eff_freq sysfs (%pe)", ERR_PTR(ret));
 	}
 
+	if (intel_uc_uses_guc_slpc(&gt->uc)) {
+		ret = sysfs_create_file(kobj, &attr_slpc_power_profile.attr);
+		if (ret)
+			gt_warn(gt, "failed to create slpc_power_profile sysfs (%pe)",
+				ERR_PTR(ret));
+	}
+
 	if (i915_mmio_reg_valid(intel_gt_perf_limit_reasons_reg(gt))) {
 		ret = sysfs_create_files(kobj, throttle_reason_attrs);
 		if (ret)

drivers/gpu/drm/i915/gt/intel_rps.c

@@ -1024,6 +1024,10 @@ void intel_rps_boost(struct i915_request *rq)
 		if (rps_uses_slpc(rps)) {
 			slpc = rps_to_slpc(rps);
 
+			/* Waitboost should not be done with power saving profile */
+			if (slpc->power_profile == SLPC_POWER_PROFILES_POWER_SAVING)
+				return;
+
 			if (slpc->min_freq_softlimit >= slpc->boost_freq)
 				return;
 

drivers/gpu/drm/i915/gt/uc/abi/guc_actions_slpc_abi.h

@@ -228,6 +228,11 @@ struct slpc_optimized_strategies {
 
 #define SLPC_OPTIMIZED_STRATEGY_COMPUTE		REG_BIT(0)
 
+enum slpc_power_profiles {
+	SLPC_POWER_PROFILES_BASE = 0x0,
+	SLPC_POWER_PROFILES_POWER_SAVING = 0x1
+};
+
 /**
  * DOC: SLPC H2G MESSAGE FORMAT
  *

drivers/gpu/drm/i915/gt/uc/intel_guc_slpc.c

@@ -15,6 +15,34 @@
 #include "gt/intel_gt_regs.h"
 #include "gt/intel_rps.h"
 
+/**
+ * DOC: SLPC - Dynamic Frequency management
+ *
+ * Single Loop Power Control (SLPC) is a GuC algorithm that manages
+ * GT frequency based on busyness and how KMD initializes it. SLPC is
+ * almost completely in control after initialization except for a few
+ * scenarios mentioned below.
+ *
+ * KMD uses the concept of waitboost to ramp frequency to RP0 when there
+ * are pending submissions for a context. It achieves this by sending GuC a
+ * request to update the min frequency to RP0. Waitboost is disabled
+ * when the request retires.
+ *
+ * Another form of frequency control happens through per-context hints.
+ * A context can be marked as low latency during creation. That will ensure
+ * that SLPC uses an aggressive frequency ramp when that context is active.
+ *
+ * Power profiles add another level of control to these mechanisms.
+ * When power saving profile is chosen, SLPC will use conservative
+ * thresholds to ramp frequency, thus saving power. KMD will disable
+ * waitboosts as well, which achieves further power savings. Base profile
+ * is default and ensures balanced performance for any workload.
+ *
+ * Lastly, users have some level of control through sysfs, where min/max
+ * frequency values can be altered and the use of efficient freq
+ * can be toggled.
+ */
+
 static inline struct intel_guc *slpc_to_guc(struct intel_guc_slpc *slpc)
 {
 	return container_of(slpc, struct intel_guc, slpc);
@@ -265,6 +293,8 @@ int intel_guc_slpc_init(struct intel_guc_slpc *slpc)
 	slpc->num_boosts = 0;
 	slpc->media_ratio_mode = SLPC_MEDIA_RATIO_MODE_DYNAMIC_CONTROL;
 
+	slpc->power_profile = SLPC_POWER_PROFILES_BASE;
+
 	mutex_init(&slpc->lock);
 	INIT_WORK(&slpc->boost_work, slpc_boost_work);
 
@@ -567,6 +597,34 @@ int intel_guc_slpc_set_media_ratio_mode(struct intel_guc_slpc *slpc, u32 val)
 	return ret;
 }
 
+int intel_guc_slpc_set_power_profile(struct intel_guc_slpc *slpc, u32 val)
+{
+	struct drm_i915_private *i915 = slpc_to_i915(slpc);
+	intel_wakeref_t wakeref;
+	int ret = 0;
+
+	if (val > SLPC_POWER_PROFILES_POWER_SAVING)
+		return -EINVAL;
+
+	mutex_lock(&slpc->lock);
+	wakeref = intel_runtime_pm_get(&i915->runtime_pm);
+
+	ret = slpc_set_param(slpc,
+			     SLPC_PARAM_POWER_PROFILE,
+			     val);
+	if (ret)
+		guc_err(slpc_to_guc(slpc),
+			"Failed to set power profile to %d: %pe\n",
+			 val, ERR_PTR(ret));
+	else
+		slpc->power_profile = val;
+
+	intel_runtime_pm_put(&i915->runtime_pm, wakeref);
+	mutex_unlock(&slpc->lock);
+
+	return ret;
+}
+
 void intel_guc_pm_intrmsk_enable(struct intel_gt *gt)
 {
 	u32 pm_intrmsk_mbz = 0;
@@ -728,6 +786,13 @@ int intel_guc_slpc_enable(struct intel_guc_slpc *slpc)
 	/* Enable SLPC Optimized Strategy for compute */
 	intel_guc_slpc_set_strategy(slpc, SLPC_OPTIMIZED_STRATEGY_COMPUTE);
 
+	/* Set cached value of power_profile */
+	ret = intel_guc_slpc_set_power_profile(slpc, slpc->power_profile);
+	if (unlikely(ret)) {
+		guc_probe_error(guc, "Failed to set SLPC power profile: %pe\n", ERR_PTR(ret));
+		return ret;
+	}
+
 	return 0;
 }
 

drivers/gpu/drm/i915/gt/uc/intel_guc_slpc.h

@@ -46,5 +46,6 @@ void intel_guc_slpc_boost(struct intel_guc_slpc *slpc);
 void intel_guc_slpc_dec_waiters(struct intel_guc_slpc *slpc);
 int intel_guc_slpc_set_ignore_eff_freq(struct intel_guc_slpc *slpc, bool val);
 int intel_guc_slpc_set_strategy(struct intel_guc_slpc *slpc, u32 val);
+int intel_guc_slpc_set_power_profile(struct intel_guc_slpc *slpc, u32 val);
 
 #endif

drivers/gpu/drm/i915/gt/uc/intel_guc_slpc_types.h

@@ -33,6 +33,9 @@ struct intel_guc_slpc {
 	u32 max_freq_softlimit;
 	bool ignore_eff_freq;
 
+	/* Base or power saving */
+	u32 power_profile;
+
 	/* cached media ratio mode */
 	u32 media_ratio_mode;