Re: [PATCH 09/13] drm/i915/cnl: Invert dvfs default level.

[Mika Kahola <mika.kahola@intel.com>]

On Tue, 2017-10-03 at 00:06 -0700, Rodrigo Vivi wrote:
> According to spec "If voltage is set too low,
> it will break functionality. If voltage is set too high,
>  it will waste power."
> 
> So, let's prefer the waste of power instead of breaking
> functionality.
> 
> But also the logic of deciding the level on spec
> tells "Else, use level 2."
> So, default is actually "2", not "0".
The spec also says

"If CD clock = 168 MHz AND DDI clock ≤ 594 MHz, use level 0.
Else If CD clock = 336 MHz AND DDI clock ≤ 594 MHz, use level 1.
Else, use level 2."

Should we add check for DDI clock rate as well here?

> 
> v2: Rebase moving it up to avoid some temporary code
>     duplication.
> 
> Cc: Mika Kahola <mika.kahola@intel.com>
> Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_cdclk.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_cdclk.c
> b/drivers/gpu/drm/i915/intel_cdclk.c
> index af8411c2a6b9..7e9c4444c844 100644
> --- a/drivers/gpu/drm/i915/intel_cdclk.c
> +++ b/drivers/gpu/drm/i915/intel_cdclk.c
> @@ -1562,15 +1562,15 @@ static void cnl_set_cdclk(struct
> drm_i915_private *dev_priv,
>  	}
>  
>  	switch (cdclk) {
> -	case 528000:
> -		pcu_ack = 2;
> +	case 168000:
> +		pcu_ack = 0;
>  		break;
>  	case 336000:
>  		pcu_ack = 1;
>  		break;
> -	case 168000:
> +	case 528000:
>  	default:
> -		pcu_ack = 0;
> +		pcu_ack = 2;
>  		break;
>  	}
>  
-- 
Mika Kahola - Intel OTC

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