Revert "drm/edid: Fix csync detailed mode parsing"

This reverts commit ca62297b.

Commit ca62297b ("drm/edid: Fix csync detailed mode parsing") fixed
EDID detailed mode sync parsing. Unfortunately, there are quite a few
displays out there that have bogus (zero) sync field that are broken by
the change. Zero means analog composite sync, which is not right for
digital displays, and the modes get rejected. Regardless, it used to
work, and it needs to continue to work. Revert the change.

Rejecting modes with analog composite sync was the part that fixed the
gitlab issue 8146 [1]. We'll need to get back to the drawing board with
that.

[1] https://gitlab.freedesktop.org/drm/intel/-/issues/8146

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/8789
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/8930
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/9044
Fixes: ca62297b ("drm/edid: Fix csync detailed mode parsing")
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v6.4+
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230815101907.2900768-1-jani.nikula@intel.com

drivers/gpu/drm/drm_edid.c

@@ -3456,6 +3456,10 @@ static struct drm_display_mode *drm_mode_detailed(struct drm_connector *connecto
 			    connector->base.id, connector->name);
 		return NULL;
 	}
+	if (!(pt->misc & DRM_EDID_PT_SEPARATE_SYNC)) {
+		drm_dbg_kms(dev, "[CONNECTOR:%d:%s] Composite sync not supported\n",
+			    connector->base.id, connector->name);
+	}
 
 	/* it is incorrect if hsync/vsync width is zero */
 	if (!hsync_pulse_width || !vsync_pulse_width) {
@@ -3502,27 +3506,10 @@ static struct drm_display_mode *drm_mode_detailed(struct drm_connector *connecto
 	if (info->quirks & EDID_QUIRK_DETAILED_SYNC_PP) {
 		mode->flags |= DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC;
 	} else {
-		switch (pt->misc & DRM_EDID_PT_SYNC_MASK) {
-		case DRM_EDID_PT_ANALOG_CSYNC:
-		case DRM_EDID_PT_BIPOLAR_ANALOG_CSYNC:
-			drm_dbg_kms(dev, "[CONNECTOR:%d:%s] Analog composite sync!\n",
-				    connector->base.id, connector->name);
-			mode->flags |= DRM_MODE_FLAG_CSYNC | DRM_MODE_FLAG_NCSYNC;
-			break;
-		case DRM_EDID_PT_DIGITAL_CSYNC:
-			drm_dbg_kms(dev, "[CONNECTOR:%d:%s] Digital composite sync!\n",
-				    connector->base.id, connector->name);
-			mode->flags |= DRM_MODE_FLAG_CSYNC;
-			mode->flags |= (pt->misc & DRM_EDID_PT_HSYNC_POSITIVE) ?
-				DRM_MODE_FLAG_PCSYNC : DRM_MODE_FLAG_NCSYNC;
-			break;
-		case DRM_EDID_PT_DIGITAL_SEPARATE_SYNC:
-			mode->flags |= (pt->misc & DRM_EDID_PT_HSYNC_POSITIVE) ?
-				DRM_MODE_FLAG_PHSYNC : DRM_MODE_FLAG_NHSYNC;
-			mode->flags |= (pt->misc & DRM_EDID_PT_VSYNC_POSITIVE) ?
-				DRM_MODE_FLAG_PVSYNC : DRM_MODE_FLAG_NVSYNC;
-			break;
-		}
+		mode->flags |= (pt->misc & DRM_EDID_PT_HSYNC_POSITIVE) ?
+			DRM_MODE_FLAG_PHSYNC : DRM_MODE_FLAG_NHSYNC;
+		mode->flags |= (pt->misc & DRM_EDID_PT_VSYNC_POSITIVE) ?
+			DRM_MODE_FLAG_PVSYNC : DRM_MODE_FLAG_NVSYNC;
 	}
 
 set_size:

include/drm/drm_edid.h

@@ -61,15 +61,9 @@ struct std_timing {
 	u8 vfreq_aspect;
 } __attribute__((packed));
 
-#define DRM_EDID_PT_SYNC_MASK              (3 << 3)
-# define DRM_EDID_PT_ANALOG_CSYNC          (0 << 3)
-# define DRM_EDID_PT_BIPOLAR_ANALOG_CSYNC  (1 << 3)
-# define DRM_EDID_PT_DIGITAL_CSYNC         (2 << 3)
-#  define DRM_EDID_PT_CSYNC_ON_RGB         (1 << 1) /* analog csync only */
-#  define DRM_EDID_PT_CSYNC_SERRATE        (1 << 2)
-# define DRM_EDID_PT_DIGITAL_SEPARATE_SYNC (3 << 3)
-#  define DRM_EDID_PT_HSYNC_POSITIVE       (1 << 1) /* also digital csync */
-#  define DRM_EDID_PT_VSYNC_POSITIVE       (1 << 2)
+#define DRM_EDID_PT_HSYNC_POSITIVE (1 << 1)
+#define DRM_EDID_PT_VSYNC_POSITIVE (1 << 2)
+#define DRM_EDID_PT_SEPARATE_SYNC  (3 << 3)
 #define DRM_EDID_PT_STEREO         (1 << 5)
 #define DRM_EDID_PT_INTERLACED     (1 << 7)