drm/edid: don't modify EDID while parsing

We'll want to keep the EDID immutable while parsing. Stop modifying the
EDID because of the quirks.

In theory, this does have userspace implications, but the userspace is
supposed to use the modes exposed via KMS API, not by parsing the EDID
directly.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/45d5cf067eaad49b321ac82836090d9de524374e.1648477901.git.jani.nikula@intel.com

drivers/gpu/drm/drm_edid.c

@@ -2740,9 +2740,9 @@ static struct drm_display_mode *drm_mode_detailed(struct drm_device *dev,
 		return NULL;
 
 	if (quirks & EDID_QUIRK_135_CLOCK_TOO_HIGH)
-		timing->pixel_clock = cpu_to_le16(1088);
-
-	mode->clock = le16_to_cpu(timing->pixel_clock) * 10;
+		mode->clock = 1088 * 10;
+	else
+		mode->clock = le16_to_cpu(timing->pixel_clock) * 10;
 
 	mode->hdisplay = hactive;
 	mode->hsync_start = mode->hdisplay + hsync_offset;
@@ -2763,14 +2763,14 @@ static struct drm_display_mode *drm_mode_detailed(struct drm_device *dev,
 	drm_mode_do_interlace_quirk(mode, pt);
 
 	if (quirks & EDID_QUIRK_DETAILED_SYNC_PP) {
-		pt->misc |= DRM_EDID_PT_HSYNC_POSITIVE | DRM_EDID_PT_VSYNC_POSITIVE;
+		mode->flags |= DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC;
+	} else {
+		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;
 	}
 
-	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:
 	mode->width_mm = pt->width_mm_lo | (pt->width_height_mm_hi & 0xf0) << 4;
 	mode->height_mm = pt->height_mm_lo | (pt->width_height_mm_hi & 0xf) << 8;