i2c: i2c-stm32f7: Implement I2C release mechanism

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 <pierre-yves.mordret@st.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
index 63ea71c..0f87449 100644 (file)
--- 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_release_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);
+
+       stm32f7_i2c_hw_config(i2c_dev);
+
+       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 = stm32f7_i2c_release_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,
@@ -1474,6 +1494,7 @@ 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);
+               stm32f7_i2c_release_bus(&i2c_dev->adap);
                f7_msg->result = -EIO;
        }