[PATCH V2] drm/bridge: ti-sn65dsi86: Add support for DisplayPort mode with HPD

[John Ripple <john.ripple@keysight.com>]

Add support for DisplayPort to the bridge, which entails the following:
- Get and use an interrupt for HPD;
- Properly clear all status bits in the interrupt handler;

Signed-off-by: John Ripple <john.ripple@keysight.com>
---
V1 -> V2: Cleaned up coding style and addressed review comments

 drivers/gpu/drm/bridge/ti-sn65dsi86.c | 93 +++++++++++++++++++++++++++
 1 file changed, 93 insertions(+)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
index ae0d08e5e960..ad0393212279 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
@@ -106,10 +106,24 @@
 #define SN_PWM_EN_INV_REG			0xA5
 #define  SN_PWM_INV_MASK			BIT(0)
 #define  SN_PWM_EN_MASK				BIT(1)
+
+#define SN_IRQ_EN_REG				0xE0
+#define  IRQ_EN					BIT(0)
+
+#define SN_IRQ_EVENTS_EN_REG			0xE6
+#define  IRQ_HPD_EN				BIT(0)
+#define  HPD_INSERTION_EN			BIT(1)
+#define  HPD_REMOVAL_EN				BIT(2)
+#define  HPD_REPLUG_EN				BIT(3)
+#define  PLL_UNLOCK_EN				BIT(5)
+
 #define SN_AUX_CMD_STATUS_REG			0xF4
 #define  AUX_IRQ_STATUS_AUX_RPLY_TOUT		BIT(3)
 #define  AUX_IRQ_STATUS_AUX_SHORT		BIT(5)
 #define  AUX_IRQ_STATUS_NAT_I2C_FAIL		BIT(6)
+#define SN_IRQ_STATUS_REG			0xF5
+#define  HPD_REMOVAL_STATUS			BIT(2)
+#define  HPD_INSERTION_STATUS			BIT(1)
 
 #define MIN_DSI_CLK_FREQ_MHZ	40
 
@@ -221,6 +235,19 @@ static const struct regmap_config ti_sn65dsi86_regmap_config = {
 	.max_register = 0xFF,
 };
 
+static int ti_sn65dsi86_read(struct ti_sn65dsi86 *pdata, unsigned int reg,
+			     unsigned int *val)
+{
+	int ret;
+
+	ret = regmap_read(pdata->regmap, reg, val);
+	if (ret)
+		dev_err(pdata->dev, "fail to read raw reg %x: %d\n",
+			reg, ret);
+
+	return ret;
+}
+
 static int __maybe_unused ti_sn65dsi86_read_u16(struct ti_sn65dsi86 *pdata,
 						unsigned int reg, u16 *val)
 {
@@ -1219,12 +1246,28 @@ static void ti_sn_bridge_hpd_enable(struct drm_bridge *bridge)
 	 */
 
 	pm_runtime_get_sync(pdata->dev);
+
+	/* Enable HPD and PLL events. */
+	regmap_write(pdata->regmap, SN_IRQ_EVENTS_EN_REG,
+		     PLL_UNLOCK_EN |
+		     HPD_REPLUG_EN |
+		     HPD_REMOVAL_EN |
+		     HPD_INSERTION_EN |
+		     IRQ_HPD_EN);
+
+	regmap_update_bits(pdata->regmap, SN_IRQ_EN_REG, IRQ_EN,
+			   IRQ_EN);
 }
 
 static void ti_sn_bridge_hpd_disable(struct drm_bridge *bridge)
 {
 	struct ti_sn65dsi86 *pdata = bridge_to_ti_sn65dsi86(bridge);
 
+	/* Disable HPD and PLL events. */
+	regmap_write(pdata->regmap, SN_IRQ_EVENTS_EN_REG, 0);
+
+	regmap_update_bits(pdata->regmap, SN_IRQ_EN_REG, IRQ_EN, 0);
+
 	pm_runtime_put_autosuspend(pdata->dev);
 }
 
@@ -1309,6 +1352,32 @@ static int ti_sn_bridge_parse_dsi_host(struct ti_sn65dsi86 *pdata)
 	return 0;
 }
 
+static irqreturn_t ti_sn_bridge_interrupt(int irq, void *private)
+{
+	struct ti_sn65dsi86 *pdata = private;
+	struct drm_device *dev = pdata->bridge.dev;
+	u32 status = 0;
+	bool hpd_event = false;
+	int ret = 0;
+
+	ret = ti_sn65dsi86_read(pdata, SN_IRQ_STATUS_REG, &status);
+	if (ret)
+		return ret;
+	hpd_event = status & (HPD_REMOVAL_STATUS | HPD_INSERTION_STATUS);
+	if (status) {
+		drm_dbg(dev, "(SN_IRQ_STATUS_REG = %#x)\n", status);
+		ret = regmap_write(pdata->regmap, SN_IRQ_STATUS_REG, status);
+		if (ret)
+			return ret;
+	}
+
+	/* Only send the HPD event if we are bound with a device. */
+	if (dev && hpd_event)
+		drm_kms_helper_hotplug_event(dev);
+
+	return IRQ_HANDLED;
+}
+
 static int ti_sn_bridge_probe(struct auxiliary_device *adev,
 			      const struct auxiliary_device_id *id)
 {
@@ -1971,6 +2040,30 @@ static int ti_sn65dsi86_probe(struct i2c_client *client)
 	if (strncmp(id_buf, "68ISD   ", ARRAY_SIZE(id_buf)))
 		return dev_err_probe(dev, -EOPNOTSUPP, "unsupported device id\n");
 
+	if (client->irq) {
+		enum drm_connector_status status;
+
+		ret = devm_request_threaded_irq(pdata->dev, client->irq, NULL,
+						ti_sn_bridge_interrupt,
+						IRQF_TRIGGER_RISING |
+						IRQF_TRIGGER_FALLING |
+						IRQF_ONESHOT,
+						"ti_sn65dsi86", pdata);
+		if (ret) {
+			return dev_err_probe(dev, ret,
+					     "failed to request interrupt\n");
+		}
+
+		/*
+		 * Cleaning status register at probe is needed because if the irq is
+		 * already high, the rising/falling condition will never occurs
+		 */
+		ret = ti_sn65dsi86_read(pdata, SN_IRQ_STATUS_REG, &status);
+		ret |= regmap_write(pdata->regmap, SN_IRQ_STATUS_REG, status);
+		if (ret)
+			pr_warn("Failed to clear IRQ initial state: %d\n", ret);
+	}
+
 	/*
 	 * Break ourselves up into a collection of aux devices. The only real
 	 * motiviation here is to solve the chicken-and-egg problem of probe