Re: [PATCH 4/4] drm/panel: ilitek-ili9881c: do a soft reset in unprepare callback

[Neil Armstrong]

On 10/30/26 06:44, Icenowy Zheng wrote:
> In case of neither reset pin nor switchable power supply is available,
> the LCD module could be DC polarized (which is harmful) when the MIPI
> DSI host is shut down.
>
> It seems that do a soft reset for the LCD controller could stop the LCD
> controller from biasing the liquid crystal, thus preventing the harm.
>
> Add a soft reset after putting the LCD controller into sleep mode.
>
> Tested on a Sipeed Lichee Console 4A, which has no LCD reset pin, and
> the LCD supply is an always-on one.
>
> Signed-off-by: Icenowy Zheng <zhengxingda@xxxxxxxxxxx>
> ---
>   drivers/gpu/drm/panel/panel-ilitek-ili9881c.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c b/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c
> index 83148c40e25ca..8b874c6f7d37c 100644
> --- a/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c
> +++ b/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c
> @@ -2493,6 +2493,10 @@ static int ili9881c_unprepare(struct drm_panel *panel)
>   
>   	mipi_dsi_dcs_set_display_off_multi(&mctx);
>   	mipi_dsi_dcs_enter_sleep_mode_multi(&mctx);
> +	mipi_dsi_msleep(&mctx, 120);
> +	mipi_dsi_dcs_soft_reset_multi(&mctx);
> +	mipi_dsi_msleep(&mctx, 5);
> +
>   	regulator_disable(ctx->power);
>   	if (ctx->iovcc)
>   		regulator_disable(ctx->iovcc);

Reviewed-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx>

Thanks,
Neil