drm/edid: check basic audio support on CEA extension block

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@vger.kernel.org
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Shawn C Lee <shawn.c.lee@intel.com>
Cc: intel-gfx <intel-gfx@lists.freedesktop.org>
Signed-off-by: Cooper Chiou <cooper.chiou@intel.com>
Signed-off-by: Lee Shawn C <shawn.c.lee@intel.com>
Fixes: e28ad544f462 ("drm/edid: parse CEA blocks embedded in DisplayID")
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220324061218.32739-1-shawn.c.lee@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 6ad4361a5cbc73c30318cf45114d9e1eaea747b1..bc4a011354995fec93371fbb06fbca76a0e13105 100644 (file)
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -4776,7 +4776,8 @@ bool drm_detect_monitor_audio(struct edid *edid)
        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");