i2c: stm32f7: add SMBus-Alert support

Add support for the SMBus-Alert protocol to the STM32F7 that has
dedicated control and status logic.

If SMBus-Alert is used, the SMBALERT# pin must be configured as alternate
function for I2C Alert.
Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>
Reviewed-by: Pierre-Yves MORDRET <pierre-yves.mordret@foss.st.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/busses/i2c-stm32f7.c

@@ -51,6 +51,7 @@
 
 /* STM32F7 I2C control 1 */
 #define STM32F7_I2C_CR1_PECEN			BIT(23)
+#define STM32F7_I2C_CR1_ALERTEN			BIT(22)
 #define STM32F7_I2C_CR1_SMBHEN			BIT(20)
 #define STM32F7_I2C_CR1_WUPEN			BIT(18)
 #define STM32F7_I2C_CR1_SBC			BIT(16)
@@ -125,6 +126,7 @@
 				(((n) & STM32F7_I2C_ISR_ADDCODE_MASK) >> 17)
 #define STM32F7_I2C_ISR_DIR			BIT(16)
 #define STM32F7_I2C_ISR_BUSY			BIT(15)
+#define STM32F7_I2C_ISR_ALERT			BIT(13)
 #define STM32F7_I2C_ISR_PECERR			BIT(11)
 #define STM32F7_I2C_ISR_ARLO			BIT(9)
 #define STM32F7_I2C_ISR_BERR			BIT(8)
@@ -138,6 +140,7 @@
 #define STM32F7_I2C_ISR_TXE			BIT(0)
 
 /* STM32F7 I2C Interrupt Clear */
+#define STM32F7_I2C_ICR_ALERTCF			BIT(13)
 #define STM32F7_I2C_ICR_PECCF			BIT(11)
 #define STM32F7_I2C_ICR_ARLOCF			BIT(9)
 #define STM32F7_I2C_ICR_BERRCF			BIT(8)
@@ -278,6 +281,17 @@ struct stm32f7_i2c_msg {
 	u8 smbus_buf[I2C_SMBUS_BLOCK_MAX + 3] __aligned(4);
 };
 
+/**
+ * struct stm32f7_i2c_alert - SMBus alert specific data
+ * @setup: platform data for the smbus_alert i2c client
+ * @ara: I2C slave device used to respond to the SMBus Alert with Alert
+ * Response Address
+ */
+struct stm32f7_i2c_alert {
+	struct i2c_smbus_alert_setup setup;
+	struct i2c_client *ara;
+};
+
 /**
  * struct stm32f7_i2c_dev - private data of the controller
  * @adap: I2C adapter for this controller
@@ -310,6 +324,7 @@ struct stm32f7_i2c_msg {
  * @analog_filter: boolean to indicate enabling of the analog filter
  * @dnf_dt: value of digital filter requested via dt
  * @dnf: value of digital filter to apply
+ * @alert: SMBus alert specific data
  */
 struct stm32f7_i2c_dev {
 	struct i2c_adapter adap;
@@ -341,6 +356,7 @@ struct stm32f7_i2c_dev {
 	bool analog_filter;
 	u32 dnf_dt;
 	u32 dnf;
+	struct stm32f7_i2c_alert *alert;
 };
 
 /*
@@ -1624,6 +1640,13 @@ static irqreturn_t stm32f7_i2c_isr_error(int irq, void *data)
 		f7_msg->result = -EINVAL;
 	}
 
+	if (status & STM32F7_I2C_ISR_ALERT) {
+		dev_dbg(dev, "<%s>: SMBus alert received\n", __func__);
+		writel_relaxed(STM32F7_I2C_ICR_ALERTCF, base + STM32F7_I2C_ICR);
+		i2c_handle_smbus_alert(i2c_dev->alert->ara);
+		return IRQ_HANDLED;
+	}
+
 	if (!i2c_dev->slave_running) {
 		u32 mask;
 		/* Disable interrupts */
@@ -1990,6 +2013,42 @@ static void stm32f7_i2c_disable_smbus_host(struct stm32f7_i2c_dev *i2c_dev)
 	}
 }
 
+static int stm32f7_i2c_enable_smbus_alert(struct stm32f7_i2c_dev *i2c_dev)
+{
+	struct stm32f7_i2c_alert *alert;
+	struct i2c_adapter *adap = &i2c_dev->adap;
+	struct device *dev = i2c_dev->dev;
+	void __iomem *base = i2c_dev->base;
+
+	alert = devm_kzalloc(dev, sizeof(*alert), GFP_KERNEL);
+	if (!alert)
+		return -ENOMEM;
+
+	alert->ara = i2c_new_smbus_alert_device(adap, &alert->setup);
+	if (IS_ERR(alert->ara))
+		return PTR_ERR(alert->ara);
+
+	i2c_dev->alert = alert;
+
+	/* Enable SMBus Alert */
+	stm32f7_i2c_set_bits(base + STM32F7_I2C_CR1, STM32F7_I2C_CR1_ALERTEN);
+
+	return 0;
+}
+
+static void stm32f7_i2c_disable_smbus_alert(struct stm32f7_i2c_dev *i2c_dev)
+{
+	struct stm32f7_i2c_alert *alert = i2c_dev->alert;
+	void __iomem *base = i2c_dev->base;
+
+	if (alert) {
+		/* Disable SMBus Alert */
+		stm32f7_i2c_clr_bits(base + STM32F7_I2C_CR1,
+				     STM32F7_I2C_CR1_ALERTEN);
+		i2c_unregister_device(alert->ara);
+	}
+}
+
 static u32 stm32f7_i2c_func(struct i2c_adapter *adap)
 {
 	struct stm32f7_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
@@ -2173,6 +2232,16 @@ static int stm32f7_i2c_probe(struct platform_device *pdev)
 		}
 	}
 
+	if (of_property_read_bool(pdev->dev.of_node, "smbus-alert")) {
+		ret = stm32f7_i2c_enable_smbus_alert(i2c_dev);
+		if (ret) {
+			dev_err(i2c_dev->dev,
+				"failed to enable SMBus alert protocol (%d)\n",
+				ret);
+			goto i2c_disable_smbus_host;
+		}
+	}
+
 	dev_info(i2c_dev->dev, "STM32F7 I2C-%d bus adapter\n", adap->nr);
 
 	pm_runtime_mark_last_busy(i2c_dev->dev);
@@ -2180,6 +2249,9 @@ static int stm32f7_i2c_probe(struct platform_device *pdev)
 
 	return 0;
 
+i2c_disable_smbus_host:
+	stm32f7_i2c_disable_smbus_host(i2c_dev);
+
 i2c_adapter_remove:
 	i2c_del_adapter(adap);
 
@@ -2214,6 +2286,7 @@ static int stm32f7_i2c_remove(struct platform_device *pdev)
 {
 	struct stm32f7_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
 
+	stm32f7_i2c_disable_smbus_alert(i2c_dev);
 	stm32f7_i2c_disable_smbus_host(i2c_dev);
 
 	i2c_del_adapter(&i2c_dev->adap);