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

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Message-Id: <20200608195704.29841-1-cyrus.lien@canonical.com>
Date:   Tue,  9 Jun 2020 03:57:04 +0800
From:   Cyrus Lien <cyrus.lien@...onical.com>
To:     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: [PATCH] drm/edid: add support for min horizontal rate equal to max horizontal rate

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.

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