linux-kernel - Re: [PATCH v2] mediatek: dsi: Correct calculation formula of PHY Timing

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Date: Mon, 22 Apr 2024 06:23:34 +0000
From: CK Hu (胡俊光) <ck.hu@...iatek.com>
To: Shuijing Li (李水静) <Shuijing.Li@...iatek.com>,
	"chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>,
	Jitao Shi (石记涛) <jitao.shi@...iatek.com>,
	"daniel@...ll.ch" <daniel@...ll.ch>, "p.zabel@...gutronix.de"
	<p.zabel@...gutronix.de>, "airlied@...il.com" <airlied@...il.com>,
	"matthias.bgg@...il.com" <matthias.bgg@...il.com>,
	"angelogioacchino.delregno@...labora.com"
	<angelogioacchino.delregno@...labora.com>
CC: "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, Project_Global_Chrome_Upstream_Group
	<Project_Global_Chrome_Upstream_Group@...iatek.com>
Subject: Re: [PATCH v2] mediatek: dsi: Correct calculation formula of PHY
 Timing

Hi, Shuijing:

On Fri, 2024-04-12 at 11:11 +0800, Shuijing Li wrote:
> This patch correct calculation formula of PHY timing.
> The spec define HS-PREPARE should be from 40ns+4*UI(44ns) to
> 85ns+6*UI(91ns). But current duration is 88ns and is near the
> boundary.
> So this patch make the duration to 64ns so it is near the safe range.

Reviewed-by: CK Hu <ck.hu@...iatek.com>

> 
> Signed-off-by: Shuijing Li <shuijing.li@...iatek.com>
> ---
> Changes in v2:
> Add a commit to describe the improvements to this patch in detail,
> per suggestion frome previous thread:
> 
https://urldefense.com/v3/__https://patchwork.kernel.org/project/linux-mediatek/patch/20240315072945.19502-1-shuijing.li@mediatek.com/__;!!CTRNKA9wMg0ARbw!izTVzhN1oe9FMDawQlr9R7PNf0n6z7ZgcSw8IUcNfcZxAJQ6Rja9aHaUoL7lISbdMHUvONao6-3_wZbs0aH72A$
>  
> ---
>  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;