linux-kernel - Re: [v10,1/3] drm/dsi: transfer DSI HS packets ending at the same time

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Date:   Wed, 19 Jan 2022 09:34:43 +0100
From:   Andrzej Hajda <andrzej.hajda@...el.com>
To:     Rex-BC Chen <rex-bc.chen@...iatek.com>, <chunkuang.hu@...nel.org>,
        <matthias.bgg@...il.com>, <narmstrong@...libre.com>,
        <robert.foss@...aro.org>, <daniel@...ll.ch>, <airlied@...ux.ie>,
        <p.zabel@...gutronix.de>
CC:     <xji@...logixsemi.com>, <jitao.shi@...iatek.com>,
        <xinlei.lee@...iatek.com>,
        <angelogioacchino.delregno@...labora.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <Project_Global_Chrome_Upstream_Group@...iatek.com>
Subject: Re: [v10,1/3] drm/dsi: transfer DSI HS packets ending at the same
 time


On 19.01.2022 03:25, Rex-BC Chen wrote:
> Since a HS transmission is composed of an arbitrary number
> of bytes that may not be an integer multiple of lanes, some
> lanes may run out of data before others.
> (Defined in 6.1.3 of mipi_DSI_specification_v.01-02-00)
>
> However, for some DSI RX devices (for example, anx7625),
> there is a limitation that packet number should be the same
> on all DSI lanes. In other words, they need to end a HS at
> the same time.
>
> Because this limitation is for some specific DSI RX devices,
> it is more reasonable to put the enable control in these
> DSI RX drivers. If DSI TX driver knows the information,
> they can adjust the setting for this situation.
>
> Signed-off-by: Jitao Shi <jitao.shi@...iatek.com>
> Signed-off-by: Rex-BC Chen <rex-bc.chen@...iatek.com>
> Acked-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>

Reviewed-by: Andrzej Hajda <andrzej.hajda@...el.com>

Regards

Andrzej

> ---
>   include/drm/drm_mipi_dsi.h | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
> index 147e51b6d241..51e09a1a106a 100644
> --- a/include/drm/drm_mipi_dsi.h
> +++ b/include/drm/drm_mipi_dsi.h
> @@ -137,6 +137,8 @@ struct mipi_dsi_host *of_find_mipi_dsi_host_by_node(struct device_node *node);
>   #define MIPI_DSI_CLOCK_NON_CONTINUOUS	BIT(10)
>   /* transmit data in low power */
>   #define MIPI_DSI_MODE_LPM		BIT(11)
> +/* transmit data ending at the same time for all lanes within one hsync */
> +#define MIPI_DSI_HS_PKT_END_ALIGNED	BIT(12)
>   
>   enum mipi_dsi_pixel_format {
>   	MIPI_DSI_FMT_RGB888,