[RFC 4/4] drm/i915: Expose RPS thresholds in sysfs

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

User feedback indicates significant performance gains are possible in
specific games with non default RPS up/down thresholds.

Expose these tunables via sysfs which will allow users to achieve best
performance when running games and best power efficiency elsewhere.

Note this patch supports non GuC based platforms only.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
References: https://gitlab.freedesktop.org/drm/intel/-/issues/8389
---
 drivers/gpu/drm/i915/gt/intel_gt_sysfs_pm.c | 104 ++++++++++++++++++++
 drivers/gpu/drm/i915/gt/intel_rps.c         |   7 +-
 2 files changed, 110 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_gt_sysfs_pm.c b/drivers/gpu/drm/i915/gt/intel_gt_sysfs_pm.c
index 28f27091cd3b..df1f9ef08475 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_sysfs_pm.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt_sysfs_pm.c
@@ -671,6 +671,76 @@ static const struct attribute *media_perf_power_attrs[] = {
 	NULL
 };
 
+static ssize_t
+rps_up_threshold_pct_show(struct kobject *kobj, struct kobj_attribute *attr,
+			  char *buf)
+{
+	struct intel_gt *gt = intel_gt_sysfs_get_drvdata(kobj, attr->attr.name);
+	struct intel_rps *rps = &gt->rps;
+
+	return sysfs_emit(buf, "%u\n", intel_rps_get_up_threshold(rps));
+}
+
+static ssize_t
+rps_up_threshold_pct_store(struct kobject *kobj, struct kobj_attribute *attr,
+			   const char *buf, size_t count)
+{
+	struct intel_gt *gt = intel_gt_sysfs_get_drvdata(kobj, attr->attr.name);
+	struct intel_rps *rps = &gt->rps;
+	int ret;
+	u8 val;
+
+	ret = kstrtou8(buf, 10, &val);
+	if (ret)
+		return ret;
+
+	ret = intel_rps_set_up_threshold(rps, val);
+
+	return ret == 0 ? count : ret;
+}
+
+static struct kobj_attribute rps_up_threshold_pct =
+__ATTR(rps_up_threshold_pct, 0664,
+       rps_up_threshold_pct_show, rps_up_threshold_pct_store);
+
+static ssize_t
+rps_down_threshold_pct_show(struct kobject *kobj, struct kobj_attribute *attr,
+			    char *buf)
+{
+	struct intel_gt *gt = intel_gt_sysfs_get_drvdata(kobj, attr->attr.name);
+	struct intel_rps *rps = &gt->rps;
+
+	return sysfs_emit(buf, "%u\n", intel_rps_get_down_threshold(rps));
+}
+
+static ssize_t
+rps_down_threshold_pct_store(struct kobject *kobj, struct kobj_attribute *attr,
+			     const char *buf, size_t count)
+{
+	struct intel_gt *gt = intel_gt_sysfs_get_drvdata(kobj, attr->attr.name);
+	struct intel_rps *rps = &gt->rps;
+	int ret;
+	u8 val;
+
+	ret = kstrtou8(buf, 10, &val);
+	if (ret)
+		return ret;
+
+	ret = intel_rps_set_down_threshold(rps, val);
+
+	return ret == 0 ? count : ret;
+}
+
+static struct kobj_attribute rps_down_threshold_pct =
+__ATTR(rps_down_threshold_pct, 0664,
+       rps_down_threshold_pct_show, rps_down_threshold_pct_store);
+
+static const struct attribute * const gen6_gt_rps_attrs[] = {
+	&rps_up_threshold_pct.attr,
+	&rps_down_threshold_pct.attr,
+	NULL
+};
+
 static ssize_t
 default_min_freq_mhz_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
 {
@@ -693,9 +763,37 @@ default_max_freq_mhz_show(struct kobject *kobj, struct kobj_attribute *attr, cha
 static struct kobj_attribute default_max_freq_mhz =
 __ATTR(rps_max_freq_mhz, 0444, default_max_freq_mhz_show, NULL);
 
+static ssize_t
+default_rps_up_threshold_pct_show(struct kobject *kobj,
+				  struct kobj_attribute *attr,
+				  char *buf)
+{
+	struct intel_gt *gt = kobj_to_gt(kobj->parent);
+
+	return sysfs_emit(buf, "%u\n", gt->defaults.rps_up_threshold);
+}
+
+static struct kobj_attribute default_rps_up_threshold_pct =
+__ATTR(rps_up_threshold_pct, 0444, default_rps_up_threshold_pct_show, NULL);
+
+static ssize_t
+default_rps_down_threshold_pct_show(struct kobject *kobj,
+				    struct kobj_attribute *attr,
+				    char *buf)
+{
+	struct intel_gt *gt = kobj_to_gt(kobj->parent);
+
+	return sysfs_emit(buf, "%u\n", gt->defaults.rps_down_threshold);
+}
+
+static struct kobj_attribute default_rps_down_threshold_pct =
+__ATTR(rps_down_threshold_pct, 0444, default_rps_down_threshold_pct_show, NULL);
+
 static const struct attribute * const rps_defaults_attrs[] = {
 	&default_min_freq_mhz.attr,
 	&default_max_freq_mhz.attr,
+	&default_rps_up_threshold_pct.attr,
+	&default_rps_down_threshold_pct.attr,
 	NULL
 };
 
@@ -723,6 +821,12 @@ static int intel_sysfs_rps_init(struct intel_gt *gt, struct kobject *kobj)
 	if (IS_VALLEYVIEW(gt->i915) || IS_CHERRYVIEW(gt->i915))
 		ret = sysfs_create_file(kobj, vlv_attr);
 
+	if (is_object_gt(kobj) && !intel_uc_uses_guc_slpc(&gt->uc)) {
+		ret = sysfs_create_files(kobj, gen6_gt_rps_attrs);
+		if (ret)
+			return ret;
+	}
+
 	return ret;
 }
 
diff --git a/drivers/gpu/drm/i915/gt/intel_rps.c b/drivers/gpu/drm/i915/gt/intel_rps.c
index a5a7315f5ace..f790e81546ff 100644
--- a/drivers/gpu/drm/i915/gt/intel_rps.c
+++ b/drivers/gpu/drm/i915/gt/intel_rps.c
@@ -2588,7 +2588,12 @@ static int rps_set_threshold(struct intel_rps *rps, u8 *threshold, u8 val)
 	ret = mutex_lock_interruptible(&rps->lock);
 	if (ret)
 		return ret;
-	*threshold = val;
+	if (*threshold != val) {
+		*threshold = val;
+		intel_rps_set(rps, clamp(rps->cur_freq,
+					 rps->min_freq_softlimit,
+					 rps->max_freq_softlimit));
+	}
 	mutex_unlock(&rps->lock);
 
 	return 0;
-- 
2.37.2