linux-kernel - Re: [PATCH 1/1] drm/panel: st7703: Pick different reset sequence

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Date:   Sun, 15 Oct 2023 12:59:22 +0200
From:   Guido Günther <guido.gunther@...i.sm>
To:     Frank Oltmanns <frank@...manns.dev>
Cc:     Purism Kernel Team <kernel@...i.sm>,
        Ondrej Jirman <megous@...ous.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        "open list:DRM PANEL DRIVERS" <dri-devel@...ts.freedesktop.org>,
        open list <linux-kernel@...r.kernel.org>,
        Ondrej Jirman <megi@....cz>,
        Samuel Holland <samuel@...lland.org>
Subject: Re: [PATCH 1/1] drm/panel: st7703: Pick different reset sequence

Hi,
On Sat, Feb 11, 2023 at 06:17:48PM +0100, Frank Oltmanns wrote:
> From: Ondrej Jirman <megi@....cz>
> 
> Switching to a different reset sequence, enabling IOVCC before enabling
> VCC.
> 
> There also needs to be a delay after enabling the supplies and before
> deasserting the reset. The datasheet specifies 1ms after the supplies
> reach the required voltage. Use 10-20ms to also give the power supplies
> some time to reach the required voltage, too.
> 
> This fixes intermittent panel initialization failures and screen
> corruption during resume from sleep on panel xingbangda,xbd599 (e.g.
> used in PinePhone).
> 
> Signed-off-by: Ondrej Jirman <megi@....cz>
> Signed-off-by: Frank Oltmanns <frank@...manns.dev>
> Reported-by: Samuel Holland <samuel@...lland.org>
> ---
>  drivers/gpu/drm/panel/panel-sitronix-st7703.c | 25 ++++++++++---------
>  1 file changed, 13 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panel/panel-sitronix-st7703.c b/drivers/gpu/drm/panel/panel-sitronix-st7703.c
> index 6747ca237ced..45695aa51f62 100644
> --- a/drivers/gpu/drm/panel/panel-sitronix-st7703.c
> +++ b/drivers/gpu/drm/panel/panel-sitronix-st7703.c
> @@ -411,29 +411,30 @@ static int st7703_prepare(struct drm_panel *panel)
>  		return 0;
>  
>  	dev_dbg(ctx->dev, "Resetting the panel\n");
> -	ret = regulator_enable(ctx->vcc);
> +	gpiod_set_value_cansleep(ctx->reset_gpio, 1);
> +
> +	ret = regulator_enable(ctx->iovcc);
>  	if (ret < 0) {
> -		dev_err(ctx->dev, "Failed to enable vcc supply: %d\n", ret);
> +		dev_err(ctx->dev, "Failed to enable iovcc supply: %d\n", ret);
>  		return ret;
>  	}
> -	ret = regulator_enable(ctx->iovcc);
> +
> +	ret = regulator_enable(ctx->vcc);
>  	if (ret < 0) {
> -		dev_err(ctx->dev, "Failed to enable iovcc supply: %d\n", ret);
> -		goto disable_vcc;
> +		dev_err(ctx->dev, "Failed to enable vcc supply: %d\n", ret);
> +		regulator_disable(ctx->iovcc);
> +		return ret;
>  	}
>  
> -	gpiod_set_value_cansleep(ctx->reset_gpio, 1);
> -	usleep_range(20, 40);
> +	/* Give power supplies time to stabilize before deasserting reset. */
> +	usleep_range(10000, 20000);
> +
>  	gpiod_set_value_cansleep(ctx->reset_gpio, 0);
> -	msleep(20);
> +	usleep_range(15000, 20000);
>  
>  	ctx->prepared = true;
>  
>  	return 0;
> -
> -disable_vcc:
> -	regulator_disable(ctx->vcc);
> -	return ret;
>  }
>  
>  static const u32 mantix_bus_formats[] = {

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

Cheers,
 -- Guido

> -- 
> 2.39.1
>