linux-kernel - Re: [PATCH 1/2] drm/mediatek: dsi: Reduce the time of dsi from LP11 to sending cmd

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Message-ID: <Y7nWKRHQr9vumv0V@ravnborg.org>
Date:   Sat, 7 Jan 2023 21:29:29 +0100
From:   Sam Ravnborg <sam@...nborg.org>
To:     xinlei.lee@...iatek.com
Cc:     chunkuang.hu@...nel.org, p.zabel@...gutronix.de, airlied@...ux.ie,
        daniel@...ll.ch, matthias.bgg@...il.com,
        angelogioacchino.delregno@...labora.com, jitao.shi@...iatek.com,
        thierry.reding@...il.com, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH 1/2] drm/mediatek: dsi: Reduce the time of dsi from LP11
 to sending cmd

On Fri, Jan 06, 2023 at 11:05:20AM +0800, xinlei.lee@...iatek.com wrote:
> From: Xinlei Lee <xinlei.lee@...iatek.com>
> 
> According to Figure 16 Turnaround Procedure on page 36 in [1], you
> can see the status of LP-00 -> LP10 -> LP11. This state can correspond
> to the state of DSI from LP00 -> LP11 in mtk_dsi_lane_ready function
> in mtk_dsi.c.
> 
> LP-00 -> LP10 -> LP11 takes about 2*TLPX time (refer to [1] page 51
> to see that TLPX is 50ns).
> 
> The delay at the end of the mtk_dsi_lane_ready function should be
> greater than the 2*TLPX specified by the DSI spec, and less than
> the time specified by the DSI_RX (generally 6ms to 40ms), to avoid
> problems caused by the RX specification.
> 
> [1]:mipi_D-PHY_specification_v1-1
> 
> Fixes: 39e8d062b03c ("drm/mediatek: Keep dsi as LP00 before dcs cmds transfer")
> Signed-off-by: Xinlei Lee <xinlei.lee@...iatek.com>

Seems OK.
Acked-by: Sam Ravnborg <sam@...nborg.org>

> ---
>  drivers/gpu/drm/mediatek/mtk_dsi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index 3b7d13028fb6..9e1363c9fcdb 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -721,7 +721,7 @@ static void mtk_dsi_lane_ready(struct mtk_dsi *dsi)
>  		mtk_dsi_clk_ulp_mode_leave(dsi);
>  		mtk_dsi_lane0_ulp_mode_leave(dsi);
>  		mtk_dsi_clk_hs_mode(dsi, 0);
> -		msleep(20);
> +		usleep_range(1000, 3000);
>  		/* The reaction time after pulling up the mipi signal for dsi_rx */
>  	}
>  }
> -- 
> 2.18.0