linux-kernel - Re: [PATCH 12/12] drm/amd/display: Rewrite CalculateWriteBackDISPCLK function

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Date:   Thu, 14 Jul 2022 22:53:00 -0300
From:   André Almeida <andrealmeid@...eup.net>
To:     Maíra Canal <mairacanal@...eup.net>
Cc:     amd-gfx@...ts.freedesktop.org, Xinhui.Pan@....com,
        David Airlie <airlied@...ux.ie>, christian.koenig@....com,
        Alex Deucher <alexander.deucher@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Leo Li <sunpeng.li@....com>,
        Harry Wentland <harry.wentland@....com>,
        Aurabindo Pillai <aurabindo.pillai@....com>,
        Nicholas Kazlauskas <nicholas.kazlauskas@....com>,
        Dmytro Laktyushkin <Dmytro.Laktyushkin@....com>,
        Daniel Vetter <daniel@...ll.ch>, linux-kernel@...r.kernel.org,
        mwen@...lia.com, Isabella Basso <isabbasso@...eup.net>,
        magalilemes00@...il.com, tales.aparecida@...il.com
Subject: Re: [PATCH 12/12] drm/amd/display: Rewrite CalculateWriteBackDISPCLK
 function

Às 13:45 de 14/07/22, Maíra Canal escreveu:
> Based on the dml30_CalculateWriteBackDISPCLK, it separates the
> DISPCLK calculations on three variables, making no functional changes, in order
> to make it more readable and better express that three values are being compared
> on dml_max.
> 
> Signed-off-by: Maíra Canal <mairacanal@...eup.net>
> ---
>  .../drm/amd/display/dc/dml/display_mode_vba.c | 31 ++++++++++++-------
>  1 file changed, 20 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/dc/dml/display_mode_vba.c b/drivers/gpu/drm/amd/display/dc/dml/display_mode_vba.c
> index c5a0a3649e9a..5fc1d16a2e15 100644
> --- a/drivers/gpu/drm/amd/display/dc/dml/display_mode_vba.c
> +++ b/drivers/gpu/drm/amd/display/dc/dml/display_mode_vba.c
> @@ -1113,20 +1113,29 @@ double CalculateWriteBackDISPCLK(
>  		unsigned int HTotal,
>  		unsigned int WritebackChromaLineBufferWidth)
>  {
> -	double CalculateWriteBackDISPCLK = 1.01 * PixelClock * dml_max(
> -		dml_ceil(WritebackLumaHTaps / 4.0, 1) / WritebackHRatio,
> -		dml_max((WritebackLumaVTaps * dml_ceil(1.0 / WritebackVRatio, 1) * dml_ceil(WritebackDestinationWidth / 4.0, 1)
> +
> +	double DISPCLK_H = 0, DISPCLK_V = 0, DISPCLK_HB = 0;
> +	double CalculateWriteBackDISPCLK = 0;
> +

Small nit: no need to initialize to 0 those variables here. They are
getting initialized bellow anyway.

> +	DISPCLK_H = dml_ceil(WritebackLumaHTaps / 4.0, 1) / WritebackHRatio;
> +	DISPCLK_V = (WritebackLumaVTaps * dml_ceil(1.0 / WritebackVRatio, 1) * dml_ceil(WritebackDestinationWidth / 4.0, 1)
>  			+ dml_ceil(WritebackDestinationWidth / 4.0, 1)) / (double) HTotal + dml_ceil(1.0 / WritebackVRatio, 1)
> -			* (dml_ceil(WritebackLumaVTaps / 4.0, 1) + 4.0) / (double) HTotal,
> -			dml_ceil(1.0 / WritebackVRatio, 1) * WritebackDestinationWidth / (double) HTotal));
> +			* (dml_ceil(WritebackLumaVTaps / 4.0, 1) + 4.0) / (double) HTotal;
> +	DISPCLK_HB = dml_ceil(1.0 / WritebackVRatio, 1) * WritebackDestinationWidth / (double) HTotal;
> +
> +	CalculateWriteBackDISPCLK = 1.01 * PixelClock * dml_max3(DISPCLK_H, DISPCLK_V, DISPCLK_HB);
> +
>  	if (WritebackPixelFormat != dm_444_32) {
> -		CalculateWriteBackDISPCLK = dml_max(CalculateWriteBackDISPCLK, 1.01 * PixelClock * dml_max(
> -			dml_ceil(WritebackChromaHTaps / 2.0, 1) / (2 * WritebackHRatio),
> -			dml_max((WritebackChromaVTaps * dml_ceil(1 / (2 * WritebackVRatio), 1) * dml_ceil(WritebackDestinationWidth / 2.0 / 2.0, 1)
> -				+ dml_ceil(WritebackDestinationWidth / 2.0 / WritebackChromaLineBufferWidth, 1)) / HTotal
> -				+ dml_ceil(1 / (2 * WritebackVRatio), 1) * (dml_ceil(WritebackChromaVTaps / 4.0, 1) + 4) / HTotal,
> -				dml_ceil(1.0 / (2 * WritebackVRatio), 1) * WritebackDestinationWidth / 2.0 / HTotal)));
> +		DISPCLK_H = dml_ceil(WritebackChromaHTaps / 2.0, 1) / (2 * WritebackHRatio);
> +		DISPCLK_V = (WritebackChromaVTaps * dml_ceil(1 / (2 * WritebackVRatio), 1) *
> +				dml_ceil(WritebackDestinationWidth / 4.0, 1) +
> +				dml_ceil(WritebackDestinationWidth / 2.0 / WritebackChromaLineBufferWidth, 1)) / HTotal +
> +			dml_ceil(1 / (2 * WritebackVRatio), 1) *(dml_ceil(WritebackChromaVTaps / 4.0, 1) + 4) / HTotal;
> +		DISPCLK_HB = dml_ceil(1.0 / (2 * WritebackVRatio), 1) * WritebackDestinationWidth / 2.0 / HTotal;
> +		CalculateWriteBackDISPCLK = dml_max(CalculateWriteBackDISPCLK,
> +				1.01 * PixelClock * dml_max3(DISPCLK_H, DISPCLK_V, DISPCLK_HB));
>  	}
> +
>  	return CalculateWriteBackDISPCLK;
>  }
>