linux-kernel - Re: [PATCH] drm/edid: add support for min horizontal rate equal to max horizontal rate

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Message-ID: <20200609145745.GO6112@intel.com>
Date:   Tue, 9 Jun 2020 17:57:45 +0300
From:   Ville Syrjälä <ville.syrjala@...ux.intel.com>
To:     Cyrus Lien <cyrus.lien@...onical.com>
Cc:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/edid: add support for min horizontal rate equal to
 max horizontal rate

On Tue, Jun 09, 2020 at 03:57:04AM +0800, Cyrus Lien wrote:
> According to EDID spec, table 3.26, byte #6 and #8, which said "Minimum
> rate value shall be less than or equal to maximum rate value". The minimum
> horizontal/vertical rate value is able to be equal to maximum horizontal/
> veritcal rate value.

How does that justifiy ignoring the min value?

> 
> This change check if h/v-sync excess maximum horizontal/vertical rate if
> hmin equal to hmax or vmin equal to vmax.
> 
> Signed-off-by: Cyrus Lien <cyrus.lien@...onical.com>
> ---
>  drivers/gpu/drm/drm_edid.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index fed653f13c26..23878320eabd 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -2674,6 +2674,9 @@ mode_in_hsync_range(const struct drm_display_mode *mode,
>  	    hmax += ((t[4] & 0x08) ? 255 : 0);
>  	hsync = drm_mode_hsync(mode);
>  
> +	if (hmax == hmin)
> +		return (hsync <= hmax);
> +
>  	return (hsync <= hmax && hsync >= hmin);
>  }
>  
> @@ -2691,6 +2694,9 @@ mode_in_vsync_range(const struct drm_display_mode *mode,
>  	    vmax += ((t[4] & 0x02) ? 255 : 0);
>  	vsync = drm_mode_vrefresh(mode);
>  
> +	if (vmax == vmin)
> +		return (vsync <= vmax);
> +
>  	return (vsync <= vmax && vsync >= vmin);
>  }
>  
> -- 
> 2.25.1
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Ville Syrjälä
Intel

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