Re: [PATCH v4] drm/i915/chv: Set min freq to efficient frequency on chv

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Apr 29, 2015 at 08:23:21AM +0530, deepak.s@linux.intel.com wrote:
> From: Deepak S <deepak.s@linux.intel.com>
> 
> After feedback from the hardware team, now we set the GPU min/idel freq to RPe.
> Punit is expecting us to operate GPU between Rpe & Rp0. If we drop the
> frequency to RPn, punit is failing to change the input voltage to
> minimum :(

So far I can't reproduce this problem on my BSW. In fact what I see
that the voltage at RPn is lower than the voltage at RPe, even while
we're in rc6.

without forcewake:
RPn -> 0x66
RPe -> 0x67
RP0 -> 0x69

with forcewake:
RPn -> 0x66
RPe -> 0x76
RP0 -> 0x9d

Also asking Punit to change the frequency after the GPU has gone to
rc6 does absolutely nothing (remind anyone of VLV?). I think I need to
retest my VLV C0 to see if my earlier observations there were accurate.
The shared Vnn rail does make it harder to observe this stuff on
VLV though.

So based on my tests this patch feels a bit wrong.

> 
> Since Punit validates the rps range [RPe, RP0]. This patch
> removes unused cherryview_rps_min_freq function.
> 
> v2: Change commit message
> 
> v3: set min_freq before idle_freq (chris)
> 
> v4: Squash 'Remove unused rps min function' patch
> 
> Signed-off-by: Deepak S <deepak.s@linux.intel.com>
> Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 21 ++-------------------
>  1 file changed, 2 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index a7516ed..78c89ff 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -4715,24 +4715,6 @@ static int cherryview_rps_guar_freq(struct drm_i915_private *dev_priv)
>  	return rp1;
>  }
>  
> -static int cherryview_rps_min_freq(struct drm_i915_private *dev_priv)
> -{
> -	struct drm_device *dev = dev_priv->dev;
> -	u32 val, rpn;
> -
> -	if (dev->pdev->revision >= 0x20) {
> -		val = vlv_punit_read(dev_priv, FB_GFX_FMIN_AT_VMIN_FUSE);
> -		rpn = ((val >> FB_GFX_FMIN_AT_VMIN_FUSE_SHIFT) &
> -		       FB_GFX_FREQ_FUSE_MASK);
> -	} else { /* For pre-production hardware */
> -		val = vlv_punit_read(dev_priv, PUNIT_GPU_STATUS_REG);
> -		rpn = ((val >> PUNIT_GPU_STATIS_GFX_MIN_FREQ_SHIFT) &
> -		       PUNIT_GPU_STATUS_GFX_MIN_FREQ_MASK);
> -	}
> -
> -	return rpn;
> -}
> -
>  static int valleyview_rps_guar_freq(struct drm_i915_private *dev_priv)
>  {
>  	u32 val, rp1;
> @@ -4984,7 +4966,8 @@ static void cherryview_init_gt_powersave(struct drm_device *dev)
>  			 intel_gpu_freq(dev_priv, dev_priv->rps.rp1_freq),
>  			 dev_priv->rps.rp1_freq);
>  
> -	dev_priv->rps.min_freq = cherryview_rps_min_freq(dev_priv);
> +	/* PUnit validated range is only [RPe, RP0] */
> +	dev_priv->rps.min_freq = dev_priv->rps.efficient_freq;
>  	DRM_DEBUG_DRIVER("min GPU freq: %d MHz (%u)\n",
>  			 intel_gpu_freq(dev_priv, dev_priv->rps.min_freq),
>  			 dev_priv->rps.min_freq);
> -- 
> 1.9.1

-- 
Ville Syrjälä
Intel OTC
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