[Intel-gfx] [PATCH] drm/i915: add min freq control to debugfs

[Chris Wilson]

On Thu, 24 May 2012 09:22:23 -0700, Jesse Barnes <jbarnes at virtuousgeek.org> wrote:
> This makes for easier benchmarking and testing.  One can set a fixed
> frequency by setting min and max to the same value.
> 
> Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>
> ---
>  drivers/gpu/drm/i915/i915_debugfs.c |   70 +++++++++++++++++++++++++++++++++++
>  1 files changed, 70 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> index eb2b3c2..c0b7688 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -1765,6 +1765,68 @@ static const struct file_operations i915_max_freq_fops = {
>  };
>  
>  static ssize_t
> +i915_min_freq_read(struct file *filp,
> +		   char __user *ubuf,
> +		   size_t max,
> +		   loff_t *ppos)
> +{
> +	struct drm_device *dev = filp->private_data;
> +	drm_i915_private_t *dev_priv = dev->dev_private;
> +	char buf[80];
> +	int len;
> +
> +	len = snprintf(buf, sizeof(buf),
> +		       "min freq: %d\n", dev_priv->min_delay * 50);
> +
> +	if (len > sizeof(buf))
> +		len = sizeof(buf);
> +
> +	return simple_read_from_buffer(ubuf, max, ppos, buf, len);
> +}
> +
> +static ssize_t
> +i915_min_freq_write(struct file *filp,
> +		  const char __user *ubuf,
> +		  size_t cnt,
> +		  loff_t *ppos)
> +{
> +	struct drm_device *dev = filp->private_data;
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	char buf[20];
> +	int val = 1;
> +
> +	if (cnt > 0) {
> +		if (cnt > sizeof(buf) - 1)
> +			return -EINVAL;
> +
> +		if (copy_from_user(buf, ubuf, cnt))
> +			return -EFAULT;
> +		buf[cnt] = 0;
> +
> +		val = simple_strtoul(buf, NULL, 0);
> +	}
> +
> +	DRM_DEBUG_DRIVER("Manually setting min freq to %d\n", val);
> +
> +	/*
> +	 * Turbo will still be enabled, but won't go above the set value.
> +	 */
> +	dev_priv->min_delay = val / 50;

Do we need some sanity checking here to prevent the user from being
silly?

Looks good otherwise,
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre