drm/radeon: Extended DDC Probing for Connectors with Improperly Wired DDC Lines (here: Asus M2A-VM HDMI)

    Some integrated ATI Radeon chipset implementations with add-on HDMI card
    (e. g. Asus M2A-VM HDMI) indicate the availability of a DDC even
    when the add-on card is not plugged in or HDMI is disabled in BIOS setup.
    In this case, drm_get_edid() and drm_edid_block_valid() periodically
    dump data and kernel errors into system log files and onto terminals.
    For these connectors DDC probing is extended by a check for a correct
    EDID header. Only in case a valid EDID header is also found, the
    (HDMI or DVI) connector will be used by the Radeon driver. This prevents
    the kernel driver from useless flooding of logs and terminal sessions with
    EDID dumps and error messages.
    This patch adds a flag 'requires_extended_probe' to the radeon_connector
    structure. In function radeon_connector_needs_extended_probe() this flag
    can be set on a chipset family/vendor/connector type specific basis.
    In addition, function radeon_ddc_probe() has been adapted to perform
    extended DDC probing if required by the connector's flag.
    Requires function drm_edid_header_is_valid() in DRM module provided by
    [PATCH] drm: Separate EDID Header Check from EDID Block Check.

    Tested for kernel 2.6.35, 2.6.38 and 3.0 on Asus M2A-VM HDMI board

    BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=668196
    BugLink: http://bugs.launchpad.net/bugs/7228066

Cc: <stable@kernel.org>
Signed-off-by: Thomas Reim <reimth@gmail.com>
Reviewed-by: Alex Deucher <alexdeucher@gmail.com>
Acked-by: Stephen Michaels <Stephen.Micheals@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
index 28f4655905bc..1a858944e4f3 100644
--- a/drivers/gpu/drm/radeon/radeon_display.c
+++ b/drivers/gpu/drm/radeon/radeon_display.c
@@ -751,8 +751,17 @@ static int radeon_ddc_dump(struct drm_connector *connector)
 	if (!radeon_connector->ddc_bus)
 		return -1;
 	edid = drm_get_edid(connector, &radeon_connector->ddc_bus->adapter);
+	/* Log EDID retrieval status here. In particular with regard to
+	 * connectors with requires_extended_probe flag set, that will prevent
+	 * function radeon_dvi_detect() to fetch EDID on this connector,
+	 * as long as there is no valid EDID header found */
 	if (edid) {
+		DRM_INFO("Radeon display connector %s: Found valid EDID",
+				drm_get_connector_name(connector));
 		kfree(edid);
+	} else {
+		DRM_INFO("Radeon display connector %s: No monitor connected or invalid EDID",
+				drm_get_connector_name(connector));
 	}
 	return ret;
 }