linux-kernel - Re: [PATCH v2 1/1] drm/panel: st7703: Fix timings when entering/exiting sleep

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Date:   Tue, 29 Aug 2023 18:16:28 +0200
From:   Guido Günther <guido.gunther@...i.sm>
To:     Frank Oltmanns <frank@...manns.dev>
Cc:     Ondrej Jirman <megi@....cz>, 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>,
        Samuel Holland <samuel@...lland.org>
Subject: Re: [PATCH v2 1/1] drm/panel: st7703: Fix timings when
 entering/exiting sleep

Hi,
On Mon, Feb 13, 2023 at 01:32:38PM +0100, Frank Oltmanns wrote:
> Fix flickering of the pinephone's XDB599 panel that happens after
> resume.
> 
> Extend the delay after issuing the command to exit sleep mode from 60 to
> 120 msec as per the controller's specification.
> 
> Introduce a 120 msec delay after issuing the command to enter sleep
> mode. This is needed in order for the controller to reliably finalize
> the sleep in sequence before switching of power supply.
> 
> In contrast to the JH057N panel, the XBD599 panel does not require a 20
> msec delay after initialization and exiting sleep mode. Therefore, move
> the delay into the already existing device specific initialization
> function.
> 
> The XDB599 does not require a 20 msec delay between the SETBGP and
> SETVCOM commands. Therefore, remove the delay from the device specific
> initialization function.
> 
> Signed-off-by: Frank Oltmanns <frank@...manns.dev>
> Cc: Ondrej Jirman <megi@....cz>
> Reported-by: Samuel Holland <samuel@...lland.org>
> ---
>  drivers/gpu/drm/panel/panel-sitronix-st7703.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panel/panel-sitronix-st7703.c b/drivers/gpu/drm/panel/panel-sitronix-st7703.c
> index 6747ca237ced..c49f4ef883fc 100644
> --- a/drivers/gpu/drm/panel/panel-sitronix-st7703.c
> +++ b/drivers/gpu/drm/panel/panel-sitronix-st7703.c
> @@ -126,6 +126,7 @@ static int jh057n_init_sequence(struct st7703 *ctx)
>  				   0x18, 0x00, 0x09, 0x0E, 0x29, 0x2D, 0x3C, 0x41,
>  				   0x37, 0x07, 0x0B, 0x0D, 0x10, 0x11, 0x0F, 0x10,
>  				   0x11, 0x18);
> +	msleep(20);
>  
>  	return 0;
>  }
> @@ -273,7 +274,6 @@ static int xbd599_init_sequence(struct st7703 *ctx)
>  	mipi_dsi_dcs_write_seq(dsi, ST7703_CMD_SETBGP,
>  			       0x07, /* VREF_SEL = 4.2V */
>  			       0x07  /* NVREF_SEL = 4.2V */);
> -	msleep(20);
>  
>  	mipi_dsi_dcs_write_seq(dsi, ST7703_CMD_SETVCOM,
>  			       0x2C, /* VCOMDC_F = -0.67V */
> @@ -350,16 +350,14 @@ static int st7703_enable(struct drm_panel *panel)
>  		return ret;
>  	}
>  
> -	msleep(20);
> -
>  	ret = mipi_dsi_dcs_exit_sleep_mode(dsi);
>  	if (ret < 0) {
>  		dev_err(ctx->dev, "Failed to exit sleep mode: %d\n", ret);
>  		return ret;
>  	}
>  
> -	/* Panel is operational 120 msec after reset */
> -	msleep(60);
> +	/* It takes the controller 120 msec to wake up after sleep. */
> +	msleep(120);
>  
>  	ret = mipi_dsi_dcs_set_display_on(dsi);
>  	if (ret)
> @@ -384,6 +382,9 @@ static int st7703_disable(struct drm_panel *panel)
>  	if (ret < 0)
>  		dev_err(ctx->dev, "Failed to enter sleep mode: %d\n", ret);
>  
> +	/* It takes the controller 120 msec to enter sleep mode. */
> +	msleep(120);
> +
>  	return 0;
>  }

Tested this patch on a Librem 5 devkit.

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

Cheers,
 -- Guido

>  
> -- 
> 2.39.1
>