Re: [PATCH] drm/i915/vlv: drop punit freq staus read after setting idle

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

On Thu, Jun 05, 2014 at 01:49:34PM -0700, Jesse Barnes wrote:
> This may take awhile (~10ms), and we don't need to make noise about it.
> 
> References: https://bugs.freedesktop.org/show_bug.cgi?id=75244
> Tested-by: huax.lu@intel.com
> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index ee27d74..4eebfd8 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3227,10 +3227,6 @@ static void vlv_set_rps_idle(struct drm_i915_private *dev_priv)
>  	vlv_punit_write(dev_priv, PUNIT_REG_GPU_FREQ_REQ,
>  					dev_priv->rps.min_freq_softlimit);
>  
> -	if (wait_for(((vlv_punit_read(dev_priv, PUNIT_REG_GPU_FREQ_STS))
> -				& GENFREQSTATUS) == 0, 5))
> -		DRM_ERROR("timed out waiting for Punit\n");
> -

As I recall the entire point of this was to make sure the frequency
really drops before we allow turning off the clock. I'm not sure if we
can trust that the frequency (and more importantly the voltage) will
drop if we allow turning off the clock before the transition is
complete.

>  	vlv_force_gfx_clock(dev_priv, false);
>  
>  	I915_WRITE(GEN6_PMINTRMSK,
> -- 
> 1.8.3.2
> 
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-- 
Ville Syrjälä
Intel OTC