linux-kernel - Re: [PATCH] mediatek: dsi: Correct calculation formula of PHY Timing

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Date: Fri, 15 Mar 2024 10:15:22 +0100
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Shuijing Li <shuijing.li@...iatek.com>, chunkuang.hu@...nel.org,
 p.zabel@...gutronix.de, airlied@...il.com, daniel@...ll.ch,
 matthias.bgg@...il.com, jitao.shi@...iatek.com
Cc: dri-devel@...ts.freedesktop.org, linux-mediatek@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH] mediatek: dsi: Correct calculation formula of PHY Timing

Il 15/03/24 08:29, Shuijing Li ha scritto:
> This patch correct calculation formula of PHY timing.
> Make actual phy timing more accurate.
> 

More accurate in which cases? By how much? On which SoC(s)?

I agree about those changes if those are improving the PHY timing, but
can you please document what's going on?

Thanks,
Angelo

> Signed-off-by: Shuijing Li <shuijing.li@...iatek.com>
> ---
>   drivers/gpu/drm/mediatek/mtk_dsi.c | 33 +++++++++++++++---------------
>   1 file changed, 17 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index a2fdfc8ddb15..d1bd7d671880 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -235,22 +235,23 @@ static void mtk_dsi_phy_timconfig(struct mtk_dsi *dsi)
>   	u32 data_rate_mhz = DIV_ROUND_UP(dsi->data_rate, 1000000);
>   	struct mtk_phy_timing *timing = &dsi->phy_timing;
>   
> -	timing->lpx = (60 * data_rate_mhz / (8 * 1000)) + 1;
> -	timing->da_hs_prepare = (80 * data_rate_mhz + 4 * 1000) / 8000;
> -	timing->da_hs_zero = (170 * data_rate_mhz + 10 * 1000) / 8000 + 1 -
> -			     timing->da_hs_prepare;
> -	timing->da_hs_trail = timing->da_hs_prepare + 1;
> -
> -	timing->ta_go = 4 * timing->lpx - 2;
> -	timing->ta_sure = timing->lpx + 2;
> -	timing->ta_get = 4 * timing->lpx;
> -	timing->da_hs_exit = 2 * timing->lpx + 1;
> -
> -	timing->clk_hs_prepare = 70 * data_rate_mhz / (8 * 1000);
> -	timing->clk_hs_post = timing->clk_hs_prepare + 8;
> -	timing->clk_hs_trail = timing->clk_hs_prepare;
> -	timing->clk_hs_zero = timing->clk_hs_trail * 4;
> -	timing->clk_hs_exit = 2 * timing->clk_hs_trail;
> +	timing->lpx = (80 * data_rate_mhz / (8 * 1000)) + 1;
> +	timing->da_hs_prepare = (59 * data_rate_mhz + 4 * 1000) / 8000 + 1;
> +	timing->da_hs_zero = (163 * data_rate_mhz + 11 * 1000) / 8000 + 1 -
> +		timing->da_hs_prepare;
> +	timing->da_hs_trail = (78 * data_rate_mhz + 7 * 1000) / 8000 + 1;
> +
> +	timing->ta_go = 4 * timing->lpx;
> +	timing->ta_sure = 3 * timing->lpx / 2;
> +	timing->ta_get = 5 * timing->lpx;
> +	timing->da_hs_exit = (118 * data_rate_mhz / (8 * 1000)) + 1;
> +
> +	timing->clk_hs_prepare = (57 * data_rate_mhz / (8 * 1000)) + 1;
> +	timing->clk_hs_post = (65 * data_rate_mhz + 53 * 1000) / 8000 + 1;
> +	timing->clk_hs_trail = (78 * data_rate_mhz + 7 * 1000) / 8000 + 1;
> +	timing->clk_hs_zero = (330 * data_rate_mhz / (8 * 1000)) + 1 -
> +		timing->clk_hs_prepare;
> +	timing->clk_hs_exit = (118 * data_rate_mhz / (8 * 1000)) + 1;
>   
>   	timcon0 = timing->lpx | timing->da_hs_prepare << 8 |
>   		  timing->da_hs_zero << 16 | timing->da_hs_trail << 24;