[Intel-gfx] [PATCH 5/7] drm/i915: Add setters for min/max frequency

[Ben Widawsky]

Provide a standardized sysfs interface for setting min, and max
frequencies.  The code which reads the limits were lifted from the
debugfs files. As a brief explanation, the limits are similar to the CPU
p-states. We have 3 states:

RP0 - ie. max frequency
RP1 - ie. "local min" frequency
RPn - seriously lowest frequency

Initially Daniel asked me to clamp the writes to supported values, but
in conforming to the way the cpufreq drivers seem to work, instead
return -EINVAL (noticed by Jesse in discussion).

The values can be used by userspace wishing to control the limits of the
GPU (see the CC list for people who care).

CC: Arjan van de Ven <arjan at linux.intel.com>
CC: Jacob Pan <jacob.jun.pan at linux.intel.com>
CC: Daniel Vetter <daniel.vetter at ffwll.ch>
CC: Jesse Barnes <jbarnes at virtuousgeek.org>
Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
---
 drivers/gpu/drm/i915/i915_sysfs.c | 78 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 76 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_sysfs.c b/drivers/gpu/drm/i915/i915_sysfs.c
index 6c7f905..5a5e610 100644
--- a/drivers/gpu/drm/i915/i915_sysfs.c
+++ b/drivers/gpu/drm/i915/i915_sysfs.c
@@ -238,6 +238,43 @@ static ssize_t gt_max_freq_mhz_show(struct device *kdev, struct device_attribute
 	return snprintf(buf, PAGE_SIZE, "%d", ret);
 }
 
+static ssize_t gt_max_freq_mhz_store(struct device *kdev,
+				     struct device_attribute *attr,
+				     const char *buf, size_t count)
+{
+	struct drm_minor *minor = container_of(kdev, struct drm_minor, kdev);
+	struct drm_device *dev = minor->dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	u32 val, rp_state_cap, hw_max;
+	ssize_t ret;
+
+	ret = kstrtou32(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	ret = mutex_lock_interruptible(&dev->struct_mutex);
+	if (ret)
+		return ret;
+
+	rp_state_cap = I915_READ(GEN6_RP_STATE_CAP);
+	hw_max = (rp_state_cap & 0xff) * GT_FREQUENCY_MULTIPLIER;
+
+	if (val > hw_max)
+		return -EINVAL;
+
+	if (val < dev_priv->rps.min_delay)
+		val = dev_priv->rps.min_delay;
+
+	if (dev_priv->rps.cur_delay > val)
+		gen6_set_rps(dev_priv->dev, val);
+
+	dev_priv->rps.max_delay = val / GT_FREQUENCY_MULTIPLIER;
+
+	mutex_unlock(&dev->struct_mutex);
+
+	return count;
+}
+
 static ssize_t gt_min_freq_mhz_show(struct device *kdev, struct device_attribute *attr, char *buf)
 {
 	struct drm_minor *minor = container_of(kdev, struct drm_minor, kdev);
@@ -255,9 +292,46 @@ static ssize_t gt_min_freq_mhz_show(struct device *kdev, struct device_attribute
 	return snprintf(buf, PAGE_SIZE, "%d", ret);
 }
 
+static ssize_t gt_min_freq_mhz_store(struct device *kdev,
+				     struct device_attribute *attr,
+				     const char *buf, size_t count)
+{
+	struct drm_minor *minor = container_of(kdev, struct drm_minor, kdev);
+	struct drm_device *dev = minor->dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	u32 val, rp_state_cap, hw_min;
+	ssize_t ret;
+
+	ret = kstrtou32(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	ret = mutex_lock_interruptible(&dev->struct_mutex);
+	if (ret)
+		return ret;
+
+	rp_state_cap = I915_READ(GEN6_RP_STATE_CAP);
+	hw_min = ((rp_state_cap & 0xff0000) >> 16) * GT_FREQUENCY_MULTIPLIER;
+
+	if (val < hw_min)
+		return -EINVAL;
+
+	if (val > dev_priv->rps.max_delay)
+		val = dev_priv->rps.max_delay;
+
+	if (dev_priv->rps.cur_delay < val)
+		gen6_set_rps(dev_priv->dev, val);
+
+	dev_priv->rps.min_delay = val / GT_FREQUENCY_MULTIPLIER;
+
+	mutex_unlock(&dev->struct_mutex);
+
+	return count;
+}
+
 static DEVICE_ATTR(gt_cur_freq_mhz, S_IRUGO, gt_cur_freq_mhz_show, NULL);
-static DEVICE_ATTR(gt_max_freq_mhz, S_IRUGO | S_IWUSR, gt_max_freq_mhz_show, NULL);
-static DEVICE_ATTR(gt_min_freq_mhz, S_IRUGO | S_IWUSR, gt_min_freq_mhz_show, NULL);
+static DEVICE_ATTR(gt_max_freq_mhz, S_IRUGO | S_IWUSR, gt_max_freq_mhz_show, gt_max_freq_mhz_store);
+static DEVICE_ATTR(gt_min_freq_mhz, S_IRUGO | S_IWUSR, gt_min_freq_mhz_show, gt_min_freq_mhz_store);
 
 static const struct attribute *gen6_attrs[] = {
 	&dev_attr_gt_cur_freq_mhz.attr,
-- 
1.7.12