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

[Chris Wilson]

On Thu, 24 May 2012 09:22:23 -0700, Jesse Barnes <jbar...@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 <jbar...@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
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