[Intel-gfx] [PATCH 39/49] drm/i915/chv: use vlv_PLL_is_optimal in chv_find_best_dpll

[Jesse Barnes]

On 03/17/2015 02:40 AM, Imre Deak wrote:
> Prepare chv_find_best_dpll to be used for BXT too, where we want to
> consider the error between target and calculated frequency too when
> choosing a better PLL configuration.
> 
> No functional change.
> 
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 26 ++++++++++++++++++++------
>  1 file changed, 20 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 5874512..9ca84a2 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -786,6 +786,16 @@ static bool vlv_PLL_is_optimal(struct drm_device *dev, int target_freq,
>  			       unsigned int best_error_ppm,
>  			       unsigned int *error_ppm)
>  {
> +	/*
> +	 * For CHV ignore the error and consider only the P value.
> +	 * Prefer a bigger P value based on HW requirements.
> +	 */
> +	if (IS_CHERRYVIEW(dev)) {
> +		*error_ppm = 0;
> +
> +		return calculated_clock->p > best_clock->p;
> +	}
> +
>  	if (WARN_ON_ONCE(!target_freq))
>  		return false;
>  
> @@ -864,11 +874,13 @@ chv_find_best_dpll(const intel_limit_t *limit, struct intel_crtc *crtc,
>  		   intel_clock_t *best_clock)
>  {
>  	struct drm_device *dev = crtc->base.dev;
> +	unsigned int best_error_ppm;
>  	intel_clock_t clock;
>  	uint64_t m2;
>  	int found = false;
>  
>  	memset(best_clock, 0, sizeof(*best_clock));
> +	best_error_ppm = 1000000;
>  
>  	/*
>  	 * Based on hardware doc, the n always set to 1, and m1 always
> @@ -882,6 +894,7 @@ chv_find_best_dpll(const intel_limit_t *limit, struct intel_crtc *crtc,
>  		for (clock.p2 = limit->p2.p2_fast;
>  				clock.p2 >= limit->p2.p2_slow;
>  				clock.p2 -= clock.p2 > 10 ? 2 : 1) {
> +			unsigned int error_ppm;
>  
>  			clock.p = clock.p1 * clock.p2;
>  
> @@ -898,12 +911,13 @@ chv_find_best_dpll(const intel_limit_t *limit, struct intel_crtc *crtc,
>  			if (!intel_PLL_is_valid(dev, limit, &clock))
>  				continue;
>  
> -			/* based on hardware requirement, prefer bigger p
> -			 */
> -			if (clock.p > best_clock->p) {
> -				*best_clock = clock;
> -				found = true;
> -			}
> +			if (!vlv_PLL_is_optimal(dev, target, &clock, best_clock,
> +						best_error_ppm, &error_ppm))
> +				continue;
> +
> +			*best_clock = clock;
> +			best_error_ppm = error_ppm;
> +			found = true;
>  		}
>  	}
>  
> 

Looking at it again, maybe vlv_PLL_is_better() might be a better name.

Also, could you just make the ppm variable a scratch one and ignore it?
 It just gets set to 0 no matter what, right?

Reviewed-by: Jesse Barnes <jbarnes at virtuousgeek.org>