linux-kernel - Re: [PATCH v4] drm/mediatek: allow commands to be sent during video mode

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Message-ID: <0a331caa-7578-60f5-cbd8-f6c8c29a629f@collabora.com>
Date:   Mon, 14 Feb 2022 10:43:13 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Julien STEPHAN <jstephan@...libre.com>
Cc:     Mattijs Korpershoek <mkorpershoek@...libre.com>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "open list:DRM DRIVERS FOR MEDIATEK" 
        <dri-devel@...ts.freedesktop.org>,
        "moderated list:DRM DRIVERS FOR MEDIATEK" 
        <linux-mediatek@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] drm/mediatek: allow commands to be sent during video
 mode

Il 14/02/22 10:27, Julien STEPHAN ha scritto:
> Mipi dsi panel drivers can use mipi_dsi_dcs_{set,get}_display_brightness()
> to request backlight changes.
> 
> This can be done during panel initialization (dsi is in command mode)
> or afterwards (dsi is in Video Mode).
> 
> When the DSI is in Video Mode, all commands are rejected.
> 
> Detect current DSI mode in mtk_dsi_host_transfer() and switch modes
> temporarily to allow commands to be sent.
> 
> Signed-off-by: Julien STEPHAN <jstephan@...libre.com>
> Signed-off-by: Mattijs Korpershoek <mkorpershoek@...libre.com>

Please, next time, don't drop the tags that reviewers are giving to you, unless
the patch changes radically.

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>

> ---
> Changes in v4:
>      - fix missing space:  "ret : recv_cnt;"
> Changes in v3:
>      - increase readability of code and use correct return variable (see
>        comment
> https://lore.kernel.org/linux-mediatek/4907bdc1-b4a6-e9ad-5cfa-266fc20c0bec@collabora.com/)
> 
> Changes in v2:
>      - update commit message to be more descriptive
> 
>   drivers/gpu/drm/mediatek/mtk_dsi.c | 33 ++++++++++++++++++++++--------
>   1 file changed, 24 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index 5d90d2eb0019..abdd9cdebd86 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -891,24 +891,33 @@ static ssize_t mtk_dsi_host_transfer(struct mipi_dsi_host *host,
>   	u8 read_data[16];
>   	void *src_addr;
>   	u8 irq_flag = CMD_DONE_INT_FLAG;
> +	u32 dsi_mode;
> +	int ret;
> 
> -	if (readl(dsi->regs + DSI_MODE_CTRL) & MODE) {
> -		DRM_ERROR("dsi engine is not command mode\n");
> -		return -EINVAL;
> +	dsi_mode = readl(dsi->regs + DSI_MODE_CTRL);
> +	if (dsi_mode & MODE) {
> +		mtk_dsi_stop(dsi);
> +		ret = mtk_dsi_switch_to_cmd_mode(dsi, VM_DONE_INT_FLAG, 500);
> +		if (ret)
> +			goto restore_dsi_mode;
>   	}
> 
>   	if (MTK_DSI_HOST_IS_READ(msg->type))
>   		irq_flag |= LPRX_RD_RDY_INT_FLAG;
> 
> -	if (mtk_dsi_host_send_cmd(dsi, msg, irq_flag) < 0)
> -		return -ETIME;
> +	ret = mtk_dsi_host_send_cmd(dsi, msg, irq_flag);
> +	if (ret)
> +		goto restore_dsi_mode;
> 
> -	if (!MTK_DSI_HOST_IS_READ(msg->type))
> -		return 0;
> +	if (!MTK_DSI_HOST_IS_READ(msg->type)) {
> +		recv_cnt = 0;
> +		goto restore_dsi_mode;
> +	}
> 
>   	if (!msg->rx_buf) {
>   		DRM_ERROR("dsi receive buffer size may be NULL\n");
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		goto restore_dsi_mode;
>   	}
> 
>   	for (i = 0; i < 16; i++)
> @@ -933,7 +942,13 @@ static ssize_t mtk_dsi_host_transfer(struct mipi_dsi_host *host,
>   	DRM_INFO("dsi get %d byte data from the panel address(0x%x)\n",
>   		 recv_cnt, *((u8 *)(msg->tx_buf)));
> 
> -	return recv_cnt;
> +restore_dsi_mode:
> +	if (dsi_mode & MODE) {
> +		mtk_dsi_set_mode(dsi);
> +		mtk_dsi_start(dsi);
> +	}
> +
> +	return ret < 0 ? ret : recv_cnt;
>   }
> 
>   static const struct mipi_dsi_host_ops mtk_dsi_ops = {
> --
> 2.35.1
>