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

[Jesse Barnes]

On Thu, 24 May 2012 20:51:40 +0100
Chris Wilson <chris at chris-wilson.co.uk> wrote:

> 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,

We'd probably want to do that on max_freq too, maybe if/when we move
this to sysfs we can track the real max/min we read from hw at init
time and clamp the values to that.

-- 
Jesse Barnes, Intel Open Source Technology Center