[PATCH v4, 4/4] drm/mediatek: Add pull-down MIPI operation in mtk_dsi_poweroff function

[CK Hu]

Hi, Xinlei:

On Mon, 2022-04-11 at 10:31 +0800, xinlei.lee at mediatek.com wrote:
> From: Xinlei Lee <xinlei.lee at mediatek.com>
> 
> In the dsi_enable function, mtk_dsi_rxtx_control is to
> pull up the MIPI signal operation. Before dsi_disable,
> MIPI should also be pulled down by writing a register 
> instead of disabling dsi.
> 
> If disable dsi without pulling the mipi signal low, the value of
> the register will still maintain the setting of the mipi signal being
> pulled high.
> After resume, even if the mipi signal is not pulled high, it will
> still
> be in the high state.

After add Fixes tag for [1], then

Reviewed-by: CK Hu <ck.hu at mediatek.com>

[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=2e54c14e310f655bb0915413e8e4a3da67c78a66

> 
> Signed-off-by: Jitao Shi <jitao.shi at mediatek.com>
> Signed-off-by: Xinlei Lee <xinlei.lee at mediatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_dsi.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c
> b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index 9ad6f08c8bfe..e35343357f90 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -676,6 +676,8 @@ static void mtk_dsi_poweroff(struct mtk_dsi *dsi)
>  	mtk_dsi_reset_engine(dsi);
>  	mtk_dsi_lane0_ulp_mode_enter(dsi);
>  	mtk_dsi_clk_ulp_mode_enter(dsi);
> +	/* set the lane number as 0 to pull down mipi */
> +	writel(0, dsi->regs + DSI_TXRX_CTRL);
>  
>  	mtk_dsi_disable(dsi);
>