[PATCH 4.19 051/338] drm/edid: check basic audio support on CEA extension block

[Greg Kroah-Hartman]

From: Cooper Chiou <cooper.chiou@xxxxxxxxx>

commit 5662abf6e21338be6d085d6375d3732ac6147fd2 upstream.

Tag code stored in bit7:5 for CTA block byte[3] is not the same as
CEA extension block definition. Only check CEA block has
basic audio support.

v3: update commit message.

Cc: stable@xxxxxxxxxxxxxxx
Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
Cc: Shawn C Lee <shawn.c.lee@xxxxxxxxx>
Cc: intel-gfx <intel-gfx@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Cooper Chiou <cooper.chiou@xxxxxxxxx>
Signed-off-by: Lee Shawn C <shawn.c.lee@xxxxxxxxx>
Fixes: e28ad544f462 ("drm/edid: parse CEA blocks embedded in DisplayID")
Reviewed-by: Jani Nikula <jani.nikula@xxxxxxxxx>
Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20220324061218.32739-1-shawn.c.lee@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/drm_edid.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -4323,7 +4323,8 @@ bool drm_detect_monitor_audio(struct edi
 	if (!edid_ext)
 		goto end;
 
-	has_audio = ((edid_ext[3] & EDID_BASIC_AUDIO) != 0);
+	has_audio = (edid_ext[0] == CEA_EXT &&
+		    (edid_ext[3] & EDID_BASIC_AUDIO) != 0);
 
 	if (has_audio) {
 		DRM_DEBUG_KMS("Monitor has basic audio support\n");