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

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Message-ID: <7a4e5afb-6947-ed7f-8555-c7402aaa3a29@collabora.com>
Date:   Mon, 11 Apr 2022 11:07:35 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.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:     dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, jitao.shi@...iatek.com,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v4, 3/4] drm/mediatek: keep dsi as LP00 before dcs cmds
 transfer

Il 11/04/22 04:31, xinlei.lee@...iatek.com ha scritto:
> 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);

This is a very long sleep, which wasn't present before this change.
Please document the reasons why we need this 20ms sleep with a comment
in the code.

Regards,
Angelo