Re: [Intel-gfx] [PATCH v2 11/11] drm/i915/dp: Reuse intel_dp_{max, effective}_data_rate in intel_link_compute_m_n()

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

On Thu, Nov 16, 2023 at 03:18:41PM +0200, Imre Deak wrote:
> Reuse intel_dp_max_data_rate() and intel_dp_effective_data_rate() in
> intel_link_compute_m_n(), instead of open-coding the equivalent. Note
> the kbit/sec -> kByte/sec unit change in the M/N values, but this not
> reducing the precision, as the link rate value is based anyway on a less
> precise 10 kbit/sec value.
> 
> Suggested-by: Jani Nikula <jani.nikula@linux.intel.com>
> Signed-off-by: Imre Deak <imre.deak@intel.com>

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

> ---
>  drivers/gpu/drm/i915/display/intel_display.c | 25 +++-----------------
>  1 file changed, 3 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index 744c321792fcf..199ecd8879461 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -2389,36 +2389,17 @@ static void compute_m_n(u32 *ret_m, u32 *ret_n,
>  	intel_reduce_m_n_ratio(ret_m, ret_n);
>  }
>  
> -static void
> -add_bw_alloc_overhead(int link_clock, int bw_overhead,
> -		      int pixel_data_rate, int link_data_rate,
> -		      u32 *data_m, u32 *data_n)
> -{
> -	bool is_uhbr = drm_dp_is_uhbr_rate(link_clock);
> -	int ch_coding_efficiency =
> -		drm_dp_bw_channel_coding_efficiency(is_uhbr);
> -
> -	*data_m = DIV_ROUND_UP_ULL(mul_u32_u32(pixel_data_rate, bw_overhead),
> -				   1000000);
> -	*data_n = DIV_ROUND_DOWN_ULL(mul_u32_u32(link_data_rate, ch_coding_efficiency),
> -				     1000000);
> -}
> -
>  void
>  intel_link_compute_m_n(u16 bits_per_pixel_x16, int nlanes,
>  		       int pixel_clock, int link_clock,
>  		       int bw_overhead,
>  		       struct intel_link_m_n *m_n)
>  {
> -	u32 data_clock = DIV_ROUND_UP(bits_per_pixel_x16 * pixel_clock, 16);
>  	u32 link_symbol_clock = intel_dp_link_symbol_clock(link_clock);
> -	u32 data_m;
> -	u32 data_n;
> +	u32 data_m = intel_dp_effective_data_rate(pixel_clock, bits_per_pixel_x16,
> +						  bw_overhead);
> +	u32 data_n = intel_dp_max_data_rate(link_clock, nlanes);
>  
> -	add_bw_alloc_overhead(link_clock, bw_overhead,
> -			      data_clock,
> -			      link_clock * 10 * nlanes,
> -			      &data_m, &data_n);
>  	/*
>  	 * Windows/BIOS uses fixed M/N values always. Follow suit.
>  	 *
> -- 
> 2.39.2

-- 
Ville Syrjälä
Intel