linux-kernel - Re: [PATCH v4, 1/4] drm/mediatek: Adjust the timing of mipi signal from LP00 to LP11

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Message-ID: <12c7587db24f0f72e8f7d30c294c7b3eac241a83.camel@mediatek.com>
Date:   Wed, 13 Apr 2022 09:59:42 +0800
From:   CK Hu <ck.hu@...iatek.com>
To:     <xinlei.lee@...iatek.com>, <chunkuang.hu@...nel.org>,
        <p.zabel@...gutronix.de>, <airlied@...ux.ie>, <daniel@...ll.ch>,
        <matthias.bgg@...il.com>, <rex-bc.chen@...iatek.com>
CC:     <jitao.shi@...iatek.com>, <linux-kernel@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>,
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4, 1/4] drm/mediatek: Adjust the timing of mipi signal
 from LP00 to LP11

Hi, Xinlei:

On Mon, 2022-04-11 at 10:31 +0800, xinlei.lee@...iatek.com wrote:
> From: Jitao Shi <jitao.shi@...iatek.com>
> 
> Old sequence:
> 1. Pull the MIPI signal high
> 2. Delay & Dsi_reset
> 3. Set the dsi timing register
> 4. dsi clk & lanes leave ulp mode and enter hs mode
> 
> The sequence after patching is:
> 1. Set the dsi timing register
> 2. Pull the MIPI signal high
> 3. Delay & Dsi_reset
> 4. dsi clk & lanes leave ulp mode and enter hs mode

You just describe WHAT this patch do, but WHY this patch do? Does this
patch reorder sequence to follow any spec?

> 
> Fixes: 2dd8075d2185 ("drm/mediatek: mtk_dsi: Use the drm_panel_bridge
> API")
> 
> Signed-off-by: Jitao Shi <jitao.shi@...iatek.com>
> Signed-off-by: Xinlei Lee <xinlei.lee@...iatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_dsi.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c
> b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index ccb0511b9cd5..262c027d8c2f 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -649,14 +649,14 @@ static int mtk_dsi_poweron(struct mtk_dsi *dsi)
>  	mtk_dsi_reset_engine(dsi);
>  	mtk_dsi_phy_timconfig(dsi);
>  
> -	mtk_dsi_rxtx_control(dsi);
> -	usleep_range(30, 100);
> -	mtk_dsi_reset_dphy(dsi);
>  	mtk_dsi_ps_control_vact(dsi);
>  	mtk_dsi_set_vm_cmd(dsi);
>  	mtk_dsi_config_vdo_timing(dsi);
>  	mtk_dsi_set_interrupt_enable(dsi);
>  
> +	mtk_dsi_rxtx_control(dsi);
> +	usleep_range(30, 100);
> +	mtk_dsi_reset_dphy(dsi);

The original sequence is done by patch [1] not the patch in the Fixes
tag. So modify the Fixes tag.

[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/gpu/drm/mediatek/mtk_dsi.c?h=v5.18-rc2&id=75374fc2c152ef42c45c6bf716743d5f5bb6d24d

Regards,
CK

>  	mtk_dsi_clk_ulp_mode_leave(dsi);
>  	mtk_dsi_lane0_ulp_mode_leave(dsi);
>  	mtk_dsi_clk_hs_mode(dsi, 0);