linux-kernel - Re: [PATCH v6 11/13] drm/panel: st7703: Assert reset prior to powering down the regulators

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Message-ID: <20200701160444.GJ174356@bogon.m.sigxcpu.org>
Date:   Wed, 1 Jul 2020 18:04:44 +0200
From:   Guido Günther <guido.gunther@...i.sm>
To:     Ondrej Jirman <megous@...ous.com>
Cc:     linux-sunxi@...glegroups.com,
        Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Purism Kernel Team <kernel@...i.sm>,
        Rob Herring <robh+dt@...nel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Icenowy Zheng <icenowy@...c.io>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Samuel Holland <samuel@...lland.org>,
        Martijn Braam <martijn@...xit.nl>, Luca Weiss <luca@...tu.xyz>,
        Bhushan Shah <bshah@....org>
Subject: Re: [PATCH v6 11/13] drm/panel: st7703: Assert reset prior to
 powering down the regulators

Hi,
On Wed, Jul 01, 2020 at 12:31:24PM +0200, Ondrej Jirman wrote:
> The reset pin is inverted, so if we don't assert reset, the actual gpio
> will be high and may keep driving the IO port of the panel.

Reviewed-by: Guido Günther <agx@...xcpu.org>

> 
> Signed-off-by: Ondrej Jirman <megous@...ous.com>
> Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
> ---
>  drivers/gpu/drm/panel/panel-sitronix-st7703.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/panel/panel-sitronix-st7703.c b/drivers/gpu/drm/panel/panel-sitronix-st7703.c
> index 0c4167994d01..e303b7b1a215 100644
> --- a/drivers/gpu/drm/panel/panel-sitronix-st7703.c
> +++ b/drivers/gpu/drm/panel/panel-sitronix-st7703.c
> @@ -417,6 +417,7 @@ static int st7703_unprepare(struct drm_panel *panel)
>  	if (!ctx->prepared)
>  		return 0;
>  
> +	gpiod_set_value_cansleep(ctx->reset_gpio, 1);
>  	regulator_disable(ctx->iovcc);
>  	regulator_disable(ctx->vcc);
>  	ctx->prepared = false;
> -- 
> 2.27.0
>