drm/i915: Add setters for min/max frequency

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. "preferred 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).

v4: Make exceeding the soft limits return -EINVAL as well (Daniel)

v3: bug fix (Ben) -  was passing the MHz value to gen6_set_rps instead of
the step value. To fix, deal only with step values by doing the divide
at the top.

v2: add the dropped mutex_unlock in error cases (Chris)
EINVAL on both too min, or too max (Daniel)

v2 Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
CC: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 81 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/i915_sysfs.c b/drivers/gpu/drm/i915/i915_sysfs.c
index 1da07e3e85af..1ffb9880d64c 100644
--- a/drivers/gpu/drm/i915/i915_sysfs.c
+++ b/drivers/gpu/drm/i915/i915_sysfs.c
@@ -238,6 +238,45 @@ 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, hw_min;
+        ssize_t ret;
+
+        ret = kstrtou32(buf, 0, &val);
+        if (ret)
+                return ret;
+
+        val /= GT_FREQUENCY_MULTIPLIER;
+
+        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);
+        hw_min = ((rp_state_cap & 0xff0000) >> 16);
+
+        if (val < hw_min || val > hw_max || val < dev_priv->rps.min_delay) {
+                mutex_unlock(&dev->struct_mutex);
+                return -EINVAL;
+        }
+
+        if (dev_priv->rps.cur_delay > val)
+                gen6_set_rps(dev_priv->dev, val);
+
+        dev_priv->rps.max_delay = val;
+
+        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 +294,49 @@ 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_max, hw_min;
+        ssize_t ret;
+
+        ret = kstrtou32(buf, 0, &val);
+        if (ret)
+                return ret;
+
+        val /= GT_FREQUENCY_MULTIPLIER;
+
+        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);
+        hw_min = ((rp_state_cap & 0xff0000) >> 16);
+
+        if (val < hw_min || val > hw_max || val > dev_priv->rps.max_delay) {
+                mutex_unlock(&dev->struct_mutex);
+                return -EINVAL;
+        }
+
+        if (dev_priv->rps.cur_delay < val)
+                gen6_set_rps(dev_priv->dev, val);
+
+        dev_priv->rps.min_delay = val;
+
+        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,