[RFC PATCH v2] staging: imx-hdmi: use rx sense status for plug detection if hpd is unreliable

[Philipp Zabel]

Due to the voltage divider on the HPD line, the HDMI connector on
imx6q-sabrelite doesn't reliably detect connected DVI monitors.
This patch allows to use the RX_SENSE0 signal as a workaround when
enabled by a boolean device tree property 'hpd-unreliable'.

Signed-off-by: Philipp Zabel <p.zabel at pengutronix.de>
---
This patch is based on Russell's recent 46-patch imx-drm cleanup series.
Changes since v1:
 - Store the status and polarity bits in struct imx_hdmi
---
 drivers/staging/imx-drm/imx-hdmi.c | 36 ++++++++++++++++++++++++++----------
 1 file changed, 26 insertions(+), 10 deletions(-)

diff --git a/drivers/staging/imx-drm/imx-hdmi.c b/drivers/staging/imx-drm/imx-hdmi.c
index fb3177d..62cb531 100644
--- a/drivers/staging/imx-drm/imx-hdmi.c
+++ b/drivers/staging/imx-drm/imx-hdmi.c
@@ -140,6 +140,9 @@ struct imx_hdmi {
 	struct regmap *regmap;
 	struct i2c_adapter *ddc;
 	void __iomem *regs;
+	u8 sink_detect_polarity;
+	u8 sink_detect_status;
+	u8 sink_detect_mask;
 
 	unsigned int sample_rate;
 	int ratio;
@@ -1317,10 +1320,10 @@ static int imx_hdmi_fb_registered(struct imx_hdmi *hdmi)
 		    HDMI_PHY_I2CM_CTLINT_ADDR);
 
 	/* enable cable hot plug irq */
-	hdmi_writeb(hdmi, (u8)~HDMI_PHY_HPD, HDMI_PHY_MASK0);
+	hdmi_writeb(hdmi, hdmi->sink_detect_mask, HDMI_PHY_MASK0);
 
 	/* Clear Hotplug interrupts */
-	hdmi_writeb(hdmi, HDMI_IH_PHY_STAT0_HPD, HDMI_IH_PHY_STAT0);
+	hdmi_writeb(hdmi, hdmi->sink_detect_status, HDMI_IH_PHY_STAT0);
 
 	return 0;
 }
@@ -1392,6 +1395,7 @@ 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;
 }
 
@@ -1530,18 +1534,20 @@ static irqreturn_t imx_hdmi_irq(int irq, void *dev_id)
 
 	phy_int_pol = hdmi_readb(hdmi, HDMI_PHY_POL0);
 
-	if (intr_stat & HDMI_IH_PHY_STAT0_HPD) {
-		if (phy_int_pol & HDMI_PHY_HPD) {
+	if (intr_stat & hdmi->sink_detect_status) {
+		int pol_bit = hdmi->sink_detect_polarity;
+
+		if (phy_int_pol & pol_bit) {
 			dev_dbg(hdmi->dev, "EVENT=plugin\n");
 
-			hdmi_modb(hdmi, 0, HDMI_PHY_HPD, HDMI_PHY_POL0);
+			hdmi_modb(hdmi, 0, pol_bit, HDMI_PHY_POL0);
 
 			hdmi->connector_status = connector_status_connected;
 			imx_hdmi_poweron(hdmi);
 		} else {
 			dev_dbg(hdmi->dev, "EVENT=plugout\n");
 
-			hdmi_modb(hdmi, HDMI_PHY_HPD, HDMI_PHY_HPD, HDMI_PHY_POL0);
+			hdmi_modb(hdmi, pol_bit, pol_bit, HDMI_PHY_POL0);
 
 			hdmi->connector_status = connector_status_disconnected;
 			imx_hdmi_poweroff(hdmi);
@@ -1550,7 +1556,7 @@ static irqreturn_t imx_hdmi_irq(int irq, void *dev_id)
 	}
 
 	hdmi_writeb(hdmi, intr_stat, HDMI_IH_PHY_STAT0);
-	hdmi_writeb(hdmi, ~HDMI_IH_PHY_STAT0_HPD, HDMI_IH_MUTE_PHY_STAT0);
+	hdmi_writeb(hdmi, ~hdmi->sink_detect_status, HDMI_IH_MUTE_PHY_STAT0);
 
 	return IRQ_HANDLED;
 }
@@ -1702,14 +1708,24 @@ static int imx_hdmi_bind(struct device *dev, struct device *master, void *data)
 	 */
 	hdmi_init_clk_regenerator(hdmi);
 
+	hdmi->sink_detect_status = HDMI_IH_PHY_STAT0_HPD;
+	hdmi->sink_detect_polarity = HDMI_PHY_HPD;
+	hdmi->sink_detect_mask = ~HDMI_PHY_HPD;
+
+	if (of_property_read_bool(np, "hpd-unreliable")) {
+		hdmi->sink_detect_status = HDMI_IH_PHY_STAT0_RX_SENSE0;
+		hdmi->sink_detect_polarity = HDMI_PHY_RX_SENSE0;
+		hdmi->sink_detect_mask = ~HDMI_PHY_RX_SENSE0;
+	}
+
 	/*
 	 * Configure registers related to HDMI interrupt
 	 * generation before registering IRQ.
 	 */
-	hdmi_writeb(hdmi, HDMI_PHY_HPD, HDMI_PHY_POL0);
+	hdmi_writeb(hdmi, hdmi->sink_detect_polarity, HDMI_PHY_POL0);
 
 	/* Clear Hotplug interrupts */
-	hdmi_writeb(hdmi, HDMI_IH_PHY_STAT0_HPD, HDMI_IH_PHY_STAT0);
+	hdmi_writeb(hdmi, hdmi->sink_detect_status, HDMI_IH_PHY_STAT0);
 
 	ret = imx_hdmi_fb_registered(hdmi);
 	if (ret)
@@ -1720,7 +1736,7 @@ static int imx_hdmi_bind(struct device *dev, struct device *master, void *data)
 		goto err_iahb;
 
 	/* Unmute interrupts */
-	hdmi_writeb(hdmi, ~HDMI_IH_PHY_STAT0_HPD, HDMI_IH_MUTE_PHY_STAT0);
+	hdmi_writeb(hdmi, ~hdmi->sink_detect_status, HDMI_IH_MUTE_PHY_STAT0);
 
 	ret = snd_dw_hdmi_probe(&hdmi->audio, dev, hdmi->regs, irq, hdmi);
 	if (ret)
-- 
1.8.5.2