[PATCH] imx-drm: fix hdmi hotplug detection initial state

[Russell King]

The initial state at boot is assumed to be disconnected, and we hope
to receive an interrupt to update the status.  Let's be more explicit
about the current state - reading the PHY status register tells us
the current level of the hotplug signal, which we can report back in
the _detect() method.

Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
---
Having discussed the issue of how to detect HDMI with David Airlie last
night, it is perfectly fine to use the HPD signal.  The reason adapters
like Intel i915 use EDID is because of cross-talk on their HPD signals,
which cause them to falsely indicate transitions when nothing has really
changed state.  So, to say that EDID polling is somehow more in keeping
with DRM than using the HPD signal is rather bogus.

The patch below fixes imx-hdmi for good systems where the HPD signal is
wired up at the board level.

 drivers/staging/imx-drm/imx-hdmi.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/staging/imx-drm/imx-hdmi.c b/drivers/staging/imx-drm/imx-hdmi.c
index d47dedd2cdb4..6f5efcc89880 100644
--- a/drivers/staging/imx-drm/imx-hdmi.c
+++ b/drivers/staging/imx-drm/imx-hdmi.c
@@ -120,8 +120,6 @@ struct imx_hdmi {
 	struct clk *isfr_clk;
 	struct clk *iahb_clk;
 
-	enum drm_connector_status connector_status;
-
 	struct hdmi_data_info hdmi_data;
 	int vic;
 
@@ -1382,7 +1380,9 @@ static enum drm_connector_status imx_hdmi_connector_detect(struct drm_connector
 {
 	struct imx_hdmi *hdmi = container_of(connector, struct imx_hdmi,
 					     connector);
-	return hdmi->connector_status;
+
+	return hdmi_readb(hdmi, HDMI_PHY_STAT0) & HDMI_PHY_HPD ?
+		connector_status_connected : connector_status_disconnected;
 }
 
 static int imx_hdmi_connector_get_modes(struct drm_connector *connector)
@@ -1524,7 +1524,6 @@ static irqreturn_t imx_hdmi_irq(int irq, void *dev_id)
 
 			hdmi_modb(hdmi, 0, HDMI_PHY_HPD, HDMI_PHY_POL0);
 
-			hdmi->connector_status = connector_status_connected;
 			imx_hdmi_poweron(hdmi);
 		} else {
 			dev_dbg(hdmi->dev, "EVENT=plugout\n");
@@ -1532,7 +1531,6 @@ static irqreturn_t imx_hdmi_irq(int irq, void *dev_id)
 			hdmi_modb(hdmi, HDMI_PHY_HPD, HDMI_PHY_HPD,
 				HDMI_PHY_POL0);
 
-			hdmi->connector_status = connector_status_disconnected;
 			imx_hdmi_poweroff(hdmi);
 		}
 		drm_helper_hpd_irq_event(hdmi->connector.dev);
@@ -1606,7 +1604,6 @@ static int imx_hdmi_bind(struct device *dev, struct device *master, void *data)
 		return -ENOMEM;
 
 	hdmi->dev = dev;
-	hdmi->connector_status = connector_status_disconnected;
 	hdmi->sample_rate = 48000;
 	hdmi->ratio = 100;
 
-- 
1.8.3.1