Re: [PATCH] drm/i915/cnl: Fix wrpll math for higher freqs.

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

On Tue, Nov 14, 2017 at 03:42:23PM -0800, Rodrigo Vivi wrote:
> Spec describe all values in MHz. We handle our
> clocks in KHz. This includes the best_dco_centrality that was
> forgot in the same unity as spec. Consequently we couldn't
> get a good divider for high frequenies. Hence HDMI 2.0 wasn't
> working.
> 
> Spec tells 999999 for initial best_dco_centrality meaning the
> max value in MHz.
> Since we convert dco from MHz to KHz we also need to convert
> this initial best_doc_centrality to 999999000 or 999999999
> or even better, to the max that its variable allow.
> 
> This patch also replaces the use of "* KHz(1)" with the values
> directly on KHz to avoid future confusion.
> 
> v2: Use U32_MAX instead of random 99999 as spec tells. (Ville).
> 
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Shashank Sharma <shashank.sharma@intel.com>
> Cc: Mika Kahola <mika.kahola@intel.com>
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> Cc: James Ausmus <james.ausmus@intel.com>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> ---
>  drivers/gpu/drm/i915/intel_dpll_mgr.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dpll_mgr.c b/drivers/gpu/drm/i915/intel_dpll_mgr.c
> index fba969cbda37..6cc12abdd39e 100644
> --- a/drivers/gpu/drm/i915/intel_dpll_mgr.c
> +++ b/drivers/gpu/drm/i915/intel_dpll_mgr.c
> @@ -2201,8 +2201,8 @@ cnl_ddi_calculate_wrpll(int clock,
>  			struct skl_wrpll_params *wrpll_params)
>  {
>  	u32 afe_clock = clock * 5;
> -	u32 dco_min = 7998 * KHz(1);
> -	u32 dco_max = 10000 * KHz(1);
> +	u32 dco_min = 7998000;
> +	u32 dco_max = 10000000;
>  	u32 dco_mid = (dco_min + dco_max) / 2;
>  	static const int dividers[] = {  2,  4,  6,  8, 10, 12,  14,  16,
>  					 18, 20, 24, 28, 30, 32,  36,  40,
> @@ -2211,7 +2211,7 @@ cnl_ddi_calculate_wrpll(int clock,
>  					 84, 88, 90, 92, 96, 98, 100, 102,
>  					  3,  5,  7,  9, 15, 21 };
>  	u32 dco, best_dco = 0, dco_centrality = 0;
> -	u32 best_dco_centrality = 999999;
> +	u32 best_dco_centrality = U32_MAX; /* Spec meaning of 999999 MHz */
>  	int d, best_div = 0, pdiv = 0, qdiv = 0, kdiv = 0;
>  
>  	for (d = 0; d < ARRAY_SIZE(dividers); d++) {
> -- 
> 2.13.6

-- 
Ville Syrjälä
Intel OTC
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx