[PATCH v4 2/2] i2c: stm32f7: add SMBus-Alert support

Alain Volmat
2021-05-05T13:20:20Z

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>
---
v4: - check for smbus-alert property
v2: - rely on st,smbus-alert binding instead of smbus
---
drivers/i2c/busses/i2c-stm32f7.c | 73 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 73 insertions(+)

diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
index 0138317ea600..b9b19a2a2ffa 100644
--- a/drivers/i2c/busses/i2c-stm32f7.c
+++ b/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)
@@ -279,6 +282,17 @@ struct stm32f7_i2c_msg {
};

/**
+ * 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
* @dev: device 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);
--
2.7.4