linux-kernel - Re: [PATCH 1/1] drm/panel: st7703: Fix vertical refresh rate of XBD599

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Date:   Sun, 19 Feb 2023 13:00:08 +0100
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>
Subject: Re: [PATCH 1/1] drm/panel: st7703: Fix vertical refresh rate of
 XBD599

Hi,
On Sun, Feb 19, 2023 at 12:45:53PM +0100, Frank Oltmanns wrote:
> Fix the XBD599 panel's slight visual stutter by correcting the pixel
> clock speed so that the panel's 60Hz vertical refresh rate is met.
> 
> Set the clock speed using the underlying formula instead of a magic
> number. To have a consistent procedure for both panels, set the JH057N
> panel's clock also as a formula.
> ---
>  drivers/gpu/drm/panel/panel-sitronix-st7703.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panel/panel-sitronix-st7703.c b/drivers/gpu/drm/panel/panel-sitronix-st7703.c
> index 6747ca237ced..cd7d631f7573 100644
> --- a/drivers/gpu/drm/panel/panel-sitronix-st7703.c
> +++ b/drivers/gpu/drm/panel/panel-sitronix-st7703.c
> @@ -139,7 +139,7 @@ static const struct drm_display_mode jh057n00900_mode = {
>  	.vsync_start = 1440 + 20,
>  	.vsync_end   = 1440 + 20 + 4,
>  	.vtotal	     = 1440 + 20 + 4 + 12,
> -	.clock	     = 75276,
> +	.clock	     = (720 + 90 + 20 + 20) * (1440 + 20 + 4 + 12) * 60 / 1000,
>  	.flags	     = DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_NVSYNC,
>  	.width_mm    = 65,
>  	.height_mm   = 130,
> @@ -324,7 +324,7 @@ static const struct drm_display_mode xbd599_mode = {
>  	.vsync_start = 1440 + 18,
>  	.vsync_end   = 1440 + 18 + 10,
>  	.vtotal	     = 1440 + 18 + 10 + 17,
> -	.clock	     = 69000,
> +	.clock	     = (720 + 40 + 40 + 40) * (1440 + 18 + 10 + 17) * 60 / 1000,
>  	.flags	     = DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_NVSYNC,
>  	.width_mm    = 68,
>  	.height_mm   = 136,

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

(I've seen your other patches but it will be some days until I can test
the jh057n00900 panel).

Cheers,
 -- Guido

> -- 
> 2.39.1
>