[PATCH] drm/vc4: Fall back to using an EDID probe in the absence of a GPIO.

From: Eric Anholt
Date: Wed Sep 14 2016 - 14:21:39 EST

On Pi0/1/2, we use an external GPIO line for hotplug detection, since
the HDMI_HOTPLUG register isn't connected to anything. However, with
the Pi3 the HPD GPIO line has moved off to a GPIO expander that will
be tricky to get to (the firmware is constantly polling the expander
using i2c0, so we'll need to coordinate with it).

As a stop-gap, if we don't have a GPIO line, use an EDID probe to
detect connection. Fixes HDMI display on the pi3.

Signed-off-by: Eric Anholt <eric@xxxxxxxxxx>
drivers/gpu/drm/vc4/vc4_hdmi.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 68ad10634b29..9f85a579da74 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -174,6 +174,9 @@ vc4_hdmi_connector_detect(struct drm_connector *connector, bool force)
return connector_status_disconnected;

+ if (drm_probe_ddc(vc4->hdmi->ddc))
+ return connector_status_connected;
return connector_status_connected;