linux-kernel - Re: [PATCH v4, 3/4] drm/mediatek: keep dsi as LP00 before dcs cmds transfer

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Date:   Wed, 13 Apr 2022 16:31:42 +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, 3/4] drm/mediatek: keep dsi as LP00 before dcs cmds
 transfer

Hi, Xinlei:

On Mon, 2022-04-11 at 10:31 +0800, xinlei.lee@...iatek.com wrote:
> From: Jitao Shi <jitao.shi@...iatek.com>
> 
> To comply with the panel sequence, hold the mipi signal to LP00
> before the dcs cmds transmission,
> and pull the mipi signal high from LP00 to LP11 until the start of
> the dcs cmds transmission.
> The normal panel timing is :
> (1) pp1800 DC pull up
> (2) avdd & avee AC pull high
> (3) lcm_reset pull high -> pull low -> pull high
> (4) Pull MIPI signal high (LP11) -> initial code -> send video
> data(HS mode)
> The power-off sequence is reversed.
> If dsi is not in cmd mode, then dsi will pull the mipi signal high in
> the mtk_output_dsi_enable function.
> 
> 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 | 28 +++++++++++++++++++++-------
>  1 file changed, 21 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c
> b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index cf76c53a1af6..9ad6f08c8bfe 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -203,6 +203,7 @@ struct mtk_dsi {
>  	struct mtk_phy_timing phy_timing;
>  	int refcount;
>  	bool enabled;
> +	bool lanes_ready;
>  	u32 irq_data;
>  	wait_queue_head_t irq_wait_queue;
>  	const struct mtk_dsi_driver_data *driver_data;
> @@ -654,13 +655,6 @@ static int mtk_dsi_poweron(struct mtk_dsi *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);
> -	mtk_dsi_clk_ulp_mode_leave(dsi);
> -	mtk_dsi_lane0_ulp_mode_leave(dsi);
> -	mtk_dsi_clk_hs_mode(dsi, 0);
> -
>  	return 0;
>  err_disable_engine_clk:
>  	clk_disable_unprepare(dsi->engine_clk);
> @@ -689,6 +683,23 @@ static void mtk_dsi_poweroff(struct mtk_dsi
> *dsi)
>  	clk_disable_unprepare(dsi->digital_clk);
>  
>  	phy_power_off(dsi->phy);
> +
> +	dsi->lanes_ready = false;
> +}
> +
> +static void mtk_dsi_lane_ready(struct mtk_dsi *dsi)
> +{
> +	if (!dsi->lanes_ready) {
> +		dsi->lanes_ready = true;
> +		mtk_dsi_rxtx_control(dsi);
> +		usleep_range(30, 100);
> +		mtk_dsi_reset_dphy(dsi);
> +		mtk_dsi_clk_ulp_mode_leave(dsi);
> +		mtk_dsi_lane0_ulp_mode_leave(dsi);
> +		mtk_dsi_clk_hs_mode(dsi, 0);
> +		msleep(20);
> +	} else
> +		DRM_DEBUG("The dsi_lane is ready\n");
>  }
>  
>  static void mtk_output_dsi_enable(struct mtk_dsi *dsi)
> @@ -696,6 +707,7 @@ static void mtk_output_dsi_enable(struct mtk_dsi
> *dsi)
>  	if (dsi->enabled)
>  		return;
>  
> +	mtk_dsi_lane_ready(dsi);
>  	mtk_dsi_set_mode(dsi);
>  	mtk_dsi_clk_hs_mode(dsi, 1);
>  
> @@ -1001,6 +1013,8 @@ static ssize_t mtk_dsi_host_transfer(struct
> mipi_dsi_host *host,
>  	if (MTK_DSI_HOST_IS_READ(msg->type))
>  		irq_flag |= LPRX_RD_RDY_INT_FLAG;
>  
> +	mtk_dsi_lane_ready(dsi);

In [1], YT has move mtk_dsi_lane_ready() before panel prepare for dsi-
>panel case. Now you move mtk_dsi_lane_ready() after panel prepare,
this may break dsi->panel case. Please provide a solution for both
case.

[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=0707632b5bacc490f58dfbad741d586c06595ff3

Regards,
CK

> +
>  	ret = mtk_dsi_host_send_cmd(dsi, msg, irq_flag);
>  	if (ret)
>  		goto restore_dsi_mode;