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From:   Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
To:     Wolfram Sang <wsa@the-dreams.de>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Alexandre Torgue <alexandre.torgue@st.com>,
        <linux-i2c@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>
CC:     Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
Subject: [PATCH v3 6/6] i2c: i2c-stm32f7: Implement I2C release mechanism
Date:   Wed, 11 Apr 2018 15:24:58 +0200
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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>
---
  Version history:
    v1:
       * Initial
    v2:
       * Don't use i2c engine recovery mechanism since driver
         procedure only recover master and not the slave.
    v3:
       * s/recovery/release/ throughout the patch. Recovery is really
         something else
---
---
 drivers/i2c/busses/i2c-stm32f7.c | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
index 63ea71c..0f87449 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_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;
 	}
 
-- 
2.7.4