Re: [PATCH 12/17] drm/i915: Don't kick the power seqeuncer just to check if we have vdd/panel power

[Imre Deak <imre.deak@intel.com>]

On Thu, 2014-10-16 at 21:29 +0300, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> If there's no power sequencer assigned to the port currently we can't
> very well have vdd or panel power enabled either. If we would try to
> check that from the pps registers we'd need to pick a power seqeuncer
> and kick it. So let's skip the register read and the kick.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 74cf827..c9a1600 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -634,6 +634,10 @@ static bool edp_have_panel_power(struct intel_dp *intel_dp)
>  
>  	lockdep_assert_held(&dev_priv->pps_mutex);
>  
> +	if (IS_VALLEYVIEW(dev) &&
> +	    intel_dp->pps_pipe == INVALID_PIPE)
> +		return false;
> +
>  	return (I915_READ(_pp_stat_reg(intel_dp)) & PP_ON) != 0;
>  }
>  
> @@ -644,6 +648,10 @@ static bool edp_have_panel_vdd(struct intel_dp *intel_dp)
>  
>  	lockdep_assert_held(&dev_priv->pps_mutex);
>  
> +	if (IS_VALLEYVIEW(dev) &&
> +	    intel_dp->pps_pipe == INVALID_PIPE)
> +		return false;
> +

During resume this makes intel_edp_panel_vdd_sanitize() think VDD is
off, though it could be left on by the BIOS. But AFAICS the above makes
also sure that VDD refcounting won't get broken even in this case. The
only issue I see is that VDD will be enabled when it was already on,
which has some overhead, but I don't think that's a priority for now.

>  	return I915_READ(_pp_ctrl_reg(intel_dp)) & EDP_FORCE_VDD;
>  }
>  

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