[PATCH 2/3] drm/bridge: dw-hdmi-qp: Add support for missing HPD

[Chris Morgan <macroalpha82@gmail.com>]

From: Chris Morgan <macromorgan@hotmail.com>

Add support for the dw-hdmi-qp driver to handle devices with missing
HPD pins.

Since in this situation we are now polling for the EDID data via i2c
change the error message to a debug message when we are unable to
complete an i2c read, as a disconnected device would otherwise fill
dmesg with i2c read errors.

Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
---
 drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c | 35 +++++++++++++++++---
 1 file changed, 31 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
index 39332c57f2c5..b221f797de3d 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
@@ -145,6 +145,7 @@ struct dw_hdmi_qp {
 	struct regmap *regm;
 
 	unsigned long tmds_char_rate;
+	bool no_hpd;
 };
 
 static void dw_hdmi_qp_write(struct dw_hdmi_qp *hdmi, unsigned int val,
@@ -520,6 +521,11 @@ static int dw_hdmi_qp_i2c_read(struct dw_hdmi_qp *hdmi,
 		i2c->is_regaddr = true;
 	}
 
+	/*
+	 * Mark errors as debug messages when using no_hpd so no device
+	 * attached does not fill up dmesg.
+	 */
+
 	while (length--) {
 		reinit_completion(&i2c->cmp);
 
@@ -535,14 +541,20 @@ static int dw_hdmi_qp_i2c_read(struct dw_hdmi_qp *hdmi,
 
 		stat = wait_for_completion_timeout(&i2c->cmp, HZ / 10);
 		if (!stat) {
-			dev_err(hdmi->dev, "i2c read timed out\n");
+			if (hdmi->no_hpd)
+				dev_dbg(hdmi->dev, "i2c read timed out\n");
+			else
+				dev_err(hdmi->dev, "i2c read timed out\n");
 			dw_hdmi_qp_write(hdmi, 0x01, I2CM_CONTROL0);
 			return -EAGAIN;
 		}
 
 		/* Check for error condition on the bus */
 		if (i2c->stat & I2CM_NACK_RCVD_IRQ) {
-			dev_err(hdmi->dev, "i2c read error\n");
+			if (hdmi->no_hpd)
+				dev_dbg(hdmi->dev, "i2c read error\n");
+			else
+				dev_err(hdmi->dev, "i2c read error\n");
 			dw_hdmi_qp_write(hdmi, 0x01, I2CM_CONTROL0);
 			return -EIO;
 		}
@@ -879,6 +891,15 @@ static enum drm_connector_status
 dw_hdmi_qp_bridge_detect(struct drm_bridge *bridge, struct drm_connector *connector)
 {
 	struct dw_hdmi_qp *hdmi = bridge->driver_private;
+	const struct drm_edid *drm_edid;
+
+	if (hdmi->no_hpd) {
+		drm_edid = drm_edid_read_ddc(connector, bridge->ddc);
+		if (drm_edid)
+			return connector_status_connected;
+		else
+			return connector_status_disconnected;
+	}
 
 	return hdmi->phy.ops->read_hpd(hdmi, hdmi->phy.data);
 }
@@ -1074,12 +1095,18 @@ struct dw_hdmi_qp *dw_hdmi_qp_bind(struct platform_device *pdev,
 	if (ret)
 		return ERR_PTR(ret);
 
+	if (of_property_present(pdev->dev.of_node, "no-hpd"))
+		hdmi->no_hpd = 1;
+	else
+		hdmi->no_hpd = 0;
+
 	hdmi->bridge.driver_private = hdmi;
 	hdmi->bridge.ops = DRM_BRIDGE_OP_DETECT |
 			   DRM_BRIDGE_OP_EDID |
 			   DRM_BRIDGE_OP_HDMI |
-			   DRM_BRIDGE_OP_HDMI_AUDIO |
-			   DRM_BRIDGE_OP_HPD;
+			   DRM_BRIDGE_OP_HDMI_AUDIO;
+	if (!hdmi->no_hpd)
+		hdmi->bridge.ops |= DRM_BRIDGE_OP_HPD;
 	hdmi->bridge.of_node = pdev->dev.of_node;
 	hdmi->bridge.type = DRM_MODE_CONNECTOR_HDMIA;
 	hdmi->bridge.vendor = "Synopsys";
-- 
2.43.0