Feature prevents I2C lock-ups. Mechanism resets I2C state machine
and releases SCL/SDA signals but preserves I2C registers.

Signed-off-by: Pierre-Yves MORDRET <redacted>
---
   Version history:
     v1:
        * Initial
---
---
  drivers/i2c/busses/i2c-stm32f7.c | 32 +++++++++++++++++++++++++++++---
  1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
index 69a2e5e..3808bc9 100644
--- a/drivers/i2c/busses/i2c-stm32f7.c
+++ b/drivers/i2c/busses/i2c-stm32f7.c

@@ -718,6 +718,20 @@ static void stm32f7_i2c_smbus_reload(struct stm32f7_i2c_dev *i2c_dev)
  	writel_relaxed(cr2, i2c_dev->base + STM32F7_I2C_CR2);
  }
  
+static int stm32f7_i2c_recover_bus(struct i2c_adapter *i2c_adap)
+{
+	struct stm32f7_i2c_dev *i2c_dev = i2c_get_adapdata(i2c_adap);
+
+	dev_info(i2c_dev->dev, "Trying to recover bus\n");
+
+	stm32f7_i2c_clr_bits(i2c_dev->base + STM32F7_I2C_CR1,
+			     STM32F7_I2C_CR1_PE);

+
+	return 0;
+}
+
  static int stm32f7_i2c_wait_free_bus(struct stm32f7_i2c_dev *i2c_dev)
  {
  	u32 status;

@@ -727,12 +741,18 @@ static int stm32f7_i2c_wait_free_bus(struct stm32f7_i2c_dev *i2c_dev)
  					 status,
  					 !(status & STM32F7_I2C_ISR_BUSY),
  					 10, 1000);
+	if (!ret)
+		return 0;
+
+	dev_info(i2c_dev->dev, "bus busy\n");
+
+	ret = i2c_recover_bus(&i2c_dev->adap);
  	if (ret) {
-		dev_dbg(i2c_dev->dev, "bus busy\n");
-		ret = -EBUSY;
+		dev_err(i2c_dev->dev, "Failed to recover the bus (%d)\n", ret);
+		return ret;
  	}
  
-	return ret;
+	return -EBUSY;
  }
  
  static void stm32f7_i2c_xfer_msg(struct stm32f7_i2c_dev *i2c_dev,

@@ -1476,6 +1496,7 @@ static irqreturn_t stm32f7_i2c_isr_error(int irq, void *data)
  	if (status & STM32F7_I2C_ISR_BERR) {
  		dev_err(dev, "<%s>: Bus error\n", __func__);
  		writel_relaxed(STM32F7_I2C_ICR_BERRCF, base + STM32F7_I2C_ICR);
+		i2c_recover_bus(&i2c_dev->adap);
  		f7_msg->result = -EIO;
  	}
  

@@ -1760,6 +1781,10 @@ static struct i2c_algorithm stm32f7_i2c_algo = {
  	.unreg_slave = stm32f7_i2c_unreg_slave,
  };
  
+static struct i2c_bus_recovery_info stm32f7_i2c_recovery_info = {
+	.recover_bus = stm32f7_i2c_recover_bus,
+};
+
  static int stm32f7_i2c_probe(struct platform_device *pdev)
  {
  	struct device_node *np = pdev->dev.of_node;

@@ -1879,6 +1904,7 @@ static int stm32f7_i2c_probe(struct platform_device *pdev)
  	adap->algo = &stm32f7_i2c_algo;
  	adap->dev.parent = &pdev->dev;
  	adap->dev.of_node = pdev->dev.of_node;
+	adap->bus_recovery_info = &stm32f7_i2c_recovery_info;
  
  	init_completion(&i2c_dev->complete);