[PATCH v3 2/6] i2c: i2c-stm32f7: Add slave support

[Pierre-Yves MORDRET <pierre-yves.mordret@st.com>]

This patch adds slave support for I2C controller embedded in STM32F7 SoC

Signed-off-by: M'boumba Cedric Madianga <cedric.madianga@gmail.com>
Signed-off-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
---
  Version history:
     v1:
        * Initial
     v2:
     v3:
---
---
 drivers/i2c/busses/Kconfig       |   1 +
 drivers/i2c/busses/i2c-stm32f7.c | 434 ++++++++++++++++++++++++++++++++++++++-
 2 files changed, 429 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 5690395..a02aab9 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -964,6 +964,7 @@ config I2C_STM32F4
 config I2C_STM32F7
 	tristate "STMicroelectronics STM32F7 I2C support"
 	depends on ARCH_STM32 || COMPILE_TEST
+	select I2C_SLAVE
 	help
 	  Enable this option to add support for STM32 I2C controller embedded
 	  in STM32F7 SoCs.
diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
index ae0d15c..9bf676e 100644
--- a/drivers/i2c/busses/i2c-stm32f7.c
+++ b/drivers/i2c/busses/i2c-stm32f7.c
@@ -35,6 +35,8 @@
 /* STM32F7 I2C registers */
 #define STM32F7_I2C_CR1				0x00
 #define STM32F7_I2C_CR2				0x04
+#define STM32F7_I2C_OAR1			0x08
+#define STM32F7_I2C_OAR2			0x0C
 #define STM32F7_I2C_TIMINGR			0x10
 #define STM32F7_I2C_ISR				0x18
 #define STM32F7_I2C_ICR				0x1C
@@ -42,6 +44,7 @@
 #define STM32F7_I2C_TXDR			0x28
 
 /* STM32F7 I2C control 1 */
+#define STM32F7_I2C_CR1_SBC			BIT(16)
 #define STM32F7_I2C_CR1_ANFOFF			BIT(12)
 #define STM32F7_I2C_CR1_ERRIE			BIT(7)
 #define STM32F7_I2C_CR1_TCIE			BIT(6)
@@ -57,6 +60,11 @@
 						| STM32F7_I2C_CR1_NACKIE \
 						| STM32F7_I2C_CR1_RXIE \
 						| STM32F7_I2C_CR1_TXIE)
+#define STM32F7_I2C_XFER_IRQ_MASK		(STM32F7_I2C_CR1_TCIE \
+						| STM32F7_I2C_CR1_STOPIE \
+						| STM32F7_I2C_CR1_NACKIE \
+						| STM32F7_I2C_CR1_RXIE \
+						| STM32F7_I2C_CR1_TXIE)
 
 /* STM32F7 I2C control 2 */
 #define STM32F7_I2C_CR2_RELOAD			BIT(24)
@@ -74,7 +82,34 @@
 #define STM32F7_I2C_CR2_SADD7_MASK		GENMASK(7, 1)
 #define STM32F7_I2C_CR2_SADD7(n)		(((n) & 0x7f) << 1)
 
+/* STM32F7 I2C Own Address 1 */
+#define STM32F7_I2C_OAR1_OA1EN			BIT(15)
+#define STM32F7_I2C_OAR1_OA1MODE		BIT(10)
+#define STM32F7_I2C_OAR1_OA1_10_MASK		GENMASK(9, 0)
+#define STM32F7_I2C_OAR1_OA1_10(n)		(((n) & \
+						STM32F7_I2C_OAR1_OA1_10_MASK))
+#define STM32F7_I2C_OAR1_OA1_7_MASK		GENMASK(7, 1)
+#define STM32F7_I2C_OAR1_OA1_7(n)		(((n) & 0x7f) << 1)
+#define STM32F7_I2C_OAR1_MASK			(STM32F7_I2C_OAR1_OA1_7_MASK \
+						| STM32F7_I2C_OAR1_OA1_10_MASK \
+						| STM32F7_I2C_OAR1_OA1EN \
+						| STM32F7_I2C_OAR1_OA1MODE)
+
+/* STM32F7 I2C Own Address 2 */
+#define STM32F7_I2C_OAR2_OA2EN			BIT(15)
+#define STM32F7_I2C_OAR2_OA2MSK_MASK		GENMASK(10, 8)
+#define STM32F7_I2C_OAR2_OA2MSK(n)		(((n) & 0x7) << 8)
+#define STM32F7_I2C_OAR2_OA2_7_MASK		GENMASK(7, 1)
+#define STM32F7_I2C_OAR2_OA2_7(n)		(((n) & 0x7f) << 1)
+#define STM32F7_I2C_OAR2_MASK			(STM32F7_I2C_OAR2_OA2MSK_MASK \
+						| STM32F7_I2C_OAR2_OA2_7_MASK \
+						| STM32F7_I2C_OAR2_OA2EN)
+
 /* STM32F7 I2C Interrupt Status */
+#define STM32F7_I2C_ISR_ADDCODE_MASK		GENMASK(23, 17)
+#define STM32F7_I2C_ISR_ADDCODE_GET(n) \
+				(((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_ARLO			BIT(9)
 #define STM32F7_I2C_ISR_BERR			BIT(8)
@@ -82,14 +117,17 @@
 #define STM32F7_I2C_ISR_TC			BIT(6)
 #define STM32F7_I2C_ISR_STOPF			BIT(5)
 #define STM32F7_I2C_ISR_NACKF			BIT(4)
+#define STM32F7_I2C_ISR_ADDR			BIT(3)
 #define STM32F7_I2C_ISR_RXNE			BIT(2)
 #define STM32F7_I2C_ISR_TXIS			BIT(1)
+#define STM32F7_I2C_ISR_TXE			BIT(0)
 
 /* STM32F7 I2C Interrupt Clear */
 #define STM32F7_I2C_ICR_ARLOCF			BIT(9)
 #define STM32F7_I2C_ICR_BERRCF			BIT(8)
 #define STM32F7_I2C_ICR_STOPCF			BIT(5)
 #define STM32F7_I2C_ICR_NACKCF			BIT(4)
+#define STM32F7_I2C_ICR_ADDRCF			BIT(3)
 
 /* STM32F7 I2C Timing */
 #define STM32F7_I2C_TIMINGR_PRESC(n)		(((n) & 0xf) << 28)
@@ -99,6 +137,7 @@
 #define STM32F7_I2C_TIMINGR_SCLL(n)		((n) & 0xff)
 
 #define STM32F7_I2C_MAX_LEN			0xff
+#define STM32F7_I2C_MAX_SLAVE			0x2
 
 #define STM32F7_I2C_DNF_DEFAULT			0
 #define STM32F7_I2C_DNF_MAX			16
@@ -209,6 +248,11 @@ struct stm32f7_i2c_msg {
  * @f7_msg: customized i2c msg for driver usage
  * @setup: I2C timing input setup
  * @timing: I2C computed timings
+ * @slave: list of slave devices registered on the I2C bus
+ * @slave_running: slave device currently used
+ * @slave_dir: transfer direction for the current slave device
+ * @master_mode: boolean to know in which mode the I2C is running (master or
+ * slave)
  */
 struct stm32f7_i2c_dev {
 	struct i2c_adapter adap;
@@ -223,6 +267,10 @@ struct stm32f7_i2c_dev {
 	struct stm32f7_i2c_msg f7_msg;
 	struct stm32f7_i2c_setup setup;
 	struct stm32f7_i2c_timings timing;
+	struct i2c_client *slave[STM32F7_I2C_MAX_SLAVE];
+	struct i2c_client *slave_running;
+	u32 slave_dir;
+	bool master_mode;
 };
 
 /**
@@ -288,6 +336,11 @@ static inline void stm32f7_i2c_clr_bits(void __iomem *reg, u32 mask)
 	writel_relaxed(readl_relaxed(reg) & ~mask, reg);
 }
 
+static void stm32f7_i2c_disable_irq(struct stm32f7_i2c_dev *i2c_dev, u32 mask)
+{
+	stm32f7_i2c_clr_bits(i2c_dev->base + STM32F7_I2C_CR1, mask);
+}
+
 static int stm32f7_i2c_compute_timing(struct stm32f7_i2c_dev *i2c_dev,
 				      struct stm32f7_i2c_setup *setup,
 				      struct stm32f7_i2c_timings *output)
@@ -572,6 +625,9 @@ static void stm32f7_i2c_read_rx_data(struct stm32f7_i2c_dev *i2c_dev)
 	if (f7_msg->count) {
 		*f7_msg->buf++ = readb_relaxed(base + STM32F7_I2C_RXDR);
 		f7_msg->count--;
+	} else {
+		/* Flush RX buffer has no data is expected */
+		readb_relaxed(base + STM32F7_I2C_RXDR);
 	}
 }
 
@@ -669,14 +725,250 @@ static void stm32f7_i2c_xfer_msg(struct stm32f7_i2c_dev *i2c_dev,
 	/* Configure Start/Repeated Start */
 	cr2 |= STM32F7_I2C_CR2_START;
 
+	i2c_dev->master_mode = true;
+
 	/* Write configurations registers */
 	writel_relaxed(cr1, base + STM32F7_I2C_CR1);
 	writel_relaxed(cr2, base + STM32F7_I2C_CR2);
 }
 
-static void stm32f7_i2c_disable_irq(struct stm32f7_i2c_dev *i2c_dev, u32 mask)
+static bool stm32f7_i2c_is_addr_match(struct i2c_client *slave, u32 addcode)
 {
-	stm32f7_i2c_clr_bits(i2c_dev->base + STM32F7_I2C_CR1, mask);
+	u32 addr;
+
+	if (!slave)
+		return false;
+
+	if (slave->flags & I2C_CLIENT_TEN) {
+		/*
+		 * For 10-bit addr, addcode = 11110XY with
+		 * X = Bit 9 of slave address
+		 * Y = Bit 8 of slave address
+		 */
+		addr = slave->addr >> 8;
+		addr |= 0x78;
+		if (addr == addcode)
+			return true;
+	} else {
+		addr = slave->addr & 0x7f;
+		if (addr == addcode)
+			return true;
+	}
+
+	return false;
+}
+
+static void stm32f7_i2c_slave_start(struct stm32f7_i2c_dev *i2c_dev)
+{
+	struct i2c_client *slave = i2c_dev->slave_running;
+	void __iomem *base = i2c_dev->base;
+	u32 mask;
+	u8 value = 0;
+
+	if (i2c_dev->slave_dir) {
+		/* Notify i2c slave that new read transfer is starting */
+		i2c_slave_event(slave, I2C_SLAVE_READ_REQUESTED, &value);
+
+		/*
+		 * Disable slave TX config in case of I2C combined message
+		 * (I2C Write followed by I2C Read)
+		 */
+		mask = STM32F7_I2C_CR2_RELOAD;
+		stm32f7_i2c_clr_bits(base + STM32F7_I2C_CR2, mask);
+		mask = STM32F7_I2C_CR1_SBC | STM32F7_I2C_CR1_RXIE |
+		       STM32F7_I2C_CR1_TCIE;
+		stm32f7_i2c_clr_bits(base + STM32F7_I2C_CR1, mask);
+
+		/* Enable TX empty, STOP, NACK interrupts */
+		mask =  STM32F7_I2C_CR1_STOPIE | STM32F7_I2C_CR1_NACKIE |
+			STM32F7_I2C_CR1_TXIE;
+		stm32f7_i2c_set_bits(base + STM32F7_I2C_CR1, mask);
+
+	} else {
+		/* Notify i2c slave that new write transfer is starting */
+		i2c_slave_event(slave, I2C_SLAVE_WRITE_REQUESTED, &value);
+
+		/* Set reload mode to be able to ACK/NACK each received byte */
+		mask = STM32F7_I2C_CR2_RELOAD;
+		stm32f7_i2c_set_bits(base + STM32F7_I2C_CR2, mask);
+
+		/*
+		 * Set STOP, NACK, RX empty and transfer complete interrupts.*
+		 * Set Slave Byte Control to be able to ACK/NACK each data
+		 * byte received
+		 */
+		mask =  STM32F7_I2C_CR1_STOPIE | STM32F7_I2C_CR1_NACKIE |
+			STM32F7_I2C_CR1_SBC | STM32F7_I2C_CR1_RXIE |
+			STM32F7_I2C_CR1_TCIE;
+		stm32f7_i2c_set_bits(base + STM32F7_I2C_CR1, mask);
+	}
+}
+
+static void stm32f7_i2c_slave_addr(struct stm32f7_i2c_dev *i2c_dev)
+{
+	void __iomem *base = i2c_dev->base;
+	u32 isr, addcode, dir, mask;
+	int i;
+
+	isr = readl_relaxed(i2c_dev->base + STM32F7_I2C_ISR);
+	addcode = STM32F7_I2C_ISR_ADDCODE_GET(isr);
+	dir = isr & STM32F7_I2C_ISR_DIR;
+
+	for (i = 0; i < STM32F7_I2C_MAX_SLAVE; i++) {
+		if (stm32f7_i2c_is_addr_match(i2c_dev->slave[i], addcode)) {
+			i2c_dev->slave_running = i2c_dev->slave[i];
+			i2c_dev->slave_dir = dir;
+
+			/* Start I2C slave processing */
+			stm32f7_i2c_slave_start(i2c_dev);
+
+			/* Clear ADDR flag */
+			mask = STM32F7_I2C_ICR_ADDRCF;
+			writel_relaxed(mask, base + STM32F7_I2C_ICR);
+			break;
+		}
+	}
+}
+
+static int stm32f7_i2c_get_slave_id(struct stm32f7_i2c_dev *i2c_dev,
+				    struct i2c_client *slave, int *id)
+{
+	int i;
+
+	for (i = 0; i < STM32F7_I2C_MAX_SLAVE; i++) {
+		if (i2c_dev->slave[i] == slave) {
+			*id = i;
+			return 0;
+		}
+	}
+
+	dev_err(i2c_dev->dev, "Slave 0x%x not registered\n", slave->addr);
+
+	return -ENODEV;
+}
+
+static int stm32f7_i2c_get_free_slave_id(struct stm32f7_i2c_dev *i2c_dev,
+					 struct i2c_client *slave, int *id)
+{
+	struct device *dev = i2c_dev->dev;
+	int i;
+
+	/*
+	 * slave[0] supports 7-bit and 10-bit slave address
+	 * slave[1] supports 7-bit slave address only
+	 */
+	for (i = 0; i < STM32F7_I2C_MAX_SLAVE; i++) {
+		if (i == 1 && (slave->flags & I2C_CLIENT_PEC))
+			continue;
+		if (!i2c_dev->slave[i]) {
+			*id = i;
+			return 0;
+		}
+	}
+
+	dev_err(dev, "Slave 0x%x could not be registered\n", slave->addr);
+
+	return -EINVAL;
+}
+
+static bool stm32f7_i2c_is_slave_registered(struct stm32f7_i2c_dev *i2c_dev)
+{
+	int i;
+
+	for (i = 0; i < STM32F7_I2C_MAX_SLAVE; i++) {
+		if (i2c_dev->slave[i])
+			return true;
+	}
+
+	return false;
+}
+
+static bool stm32f7_i2c_is_slave_busy(struct stm32f7_i2c_dev *i2c_dev)
+{
+	int i, busy;
+
+	busy = 0;
+	for (i = 0; i < STM32F7_I2C_MAX_SLAVE; i++) {
+		if (i2c_dev->slave[i])
+			busy++;
+	}
+
+	return i == busy;
+}
+
+static irqreturn_t stm32f7_i2c_slave_isr_event(struct stm32f7_i2c_dev *i2c_dev)
+{
+	void __iomem *base = i2c_dev->base;
+	u32 cr2, status, mask;
+	u8 val;
+	int ret;
+
+	status = readl_relaxed(i2c_dev->base + STM32F7_I2C_ISR);
+
+	/* Slave transmitter mode */
+	if (status & STM32F7_I2C_ISR_TXIS) {
+		i2c_slave_event(i2c_dev->slave_running,
+				I2C_SLAVE_READ_PROCESSED,
+				&val);
+
+		/* Write data byte */
+		writel_relaxed(val, base + STM32F7_I2C_TXDR);
+	}
+
+	/* Transfer Complete Reload for Slave receiver mode */
+	if (status & STM32F7_I2C_ISR_TCR || status & STM32F7_I2C_ISR_RXNE) {
+		/*
+		 * Read data byte then set NBYTES to receive next byte or NACK
+		 * the current received byte
+		 */
+		val = readb_relaxed(i2c_dev->base + STM32F7_I2C_RXDR);
+		ret = i2c_slave_event(i2c_dev->slave_running,
+				      I2C_SLAVE_WRITE_RECEIVED,
+				      &val);
+		if (!ret) {
+			cr2 = readl_relaxed(i2c_dev->base + STM32F7_I2C_CR2);
+			cr2 |= STM32F7_I2C_CR2_NBYTES(1);
+			writel_relaxed(cr2, i2c_dev->base + STM32F7_I2C_CR2);
+		} else {
+			mask = STM32F7_I2C_CR2_NACK;
+			stm32f7_i2c_set_bits(base + STM32F7_I2C_CR2, mask);
+		}
+	}
+
+	/* NACK received */
+	if (status & STM32F7_I2C_ISR_NACKF) {
+		dev_dbg(i2c_dev->dev, "<%s>: Receive NACK\n", __func__);
+		writel_relaxed(STM32F7_I2C_ICR_NACKCF, base + STM32F7_I2C_ICR);
+	}
+
+	/* STOP received */
+	if (status & STM32F7_I2C_ISR_STOPF) {
+		/* Disable interrupts */
+		stm32f7_i2c_disable_irq(i2c_dev, STM32F7_I2C_XFER_IRQ_MASK);
+
+		if (i2c_dev->slave_dir) {
+			/*
+			 * Flush TX buffer in order to not used the byte in
+			 * TXDR for the next transfer
+			 */
+			mask = STM32F7_I2C_ISR_TXE;
+			stm32f7_i2c_set_bits(base + STM32F7_I2C_ISR, mask);
+		}
+
+		/* Clear STOP flag */
+		writel_relaxed(STM32F7_I2C_ICR_STOPCF, base + STM32F7_I2C_ICR);
+
+		/* Notify i2c slave that a STOP flag has been detected */
+		i2c_slave_event(i2c_dev->slave_running, I2C_SLAVE_STOP, &val);
+
+		i2c_dev->slave_running = NULL;
+	}
+
+	/* Address match received */
+	if (status & STM32F7_I2C_ISR_ADDR)
+		stm32f7_i2c_slave_addr(i2c_dev);
+
+	return IRQ_HANDLED;
 }
 
 static irqreturn_t stm32f7_i2c_isr_event(int irq, void *data)
@@ -685,6 +977,13 @@ static irqreturn_t stm32f7_i2c_isr_event(int irq, void *data)
 	struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
 	void __iomem *base = i2c_dev->base;
 	u32 status, mask;
+	int ret;
+
+	/* Check if the interrupt if for a slave device */
+	if (!i2c_dev->master_mode) {
+		ret = stm32f7_i2c_slave_isr_event(i2c_dev);
+		return ret;
+	}
 
 	status = readl_relaxed(i2c_dev->base + STM32F7_I2C_ISR);
 
@@ -706,11 +1005,16 @@ static irqreturn_t stm32f7_i2c_isr_event(int irq, void *data)
 	/* STOP detection flag */
 	if (status & STM32F7_I2C_ISR_STOPF) {
 		/* Disable interrupts */
-		stm32f7_i2c_disable_irq(i2c_dev, STM32F7_I2C_ALL_IRQ_MASK);
+		if (stm32f7_i2c_is_slave_registered(i2c_dev))
+			mask = STM32F7_I2C_XFER_IRQ_MASK;
+		else
+			mask = STM32F7_I2C_ALL_IRQ_MASK;
+		stm32f7_i2c_disable_irq(i2c_dev, mask);
 
 		/* Clear STOP flag */
 		writel_relaxed(STM32F7_I2C_ICR_STOPCF, base + STM32F7_I2C_ICR);
 
+		i2c_dev->master_mode = false;
 		complete(&i2c_dev->complete);
 	}
 
@@ -743,7 +1047,7 @@ static irqreturn_t stm32f7_i2c_isr_error(int irq, void *data)
 	struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
 	void __iomem *base = i2c_dev->base;
 	struct device *dev = i2c_dev->dev;
-	u32 status;
+	u32 mask, status;
 
 	status = readl_relaxed(i2c_dev->base + STM32F7_I2C_ISR);
 
@@ -761,8 +1065,14 @@ static irqreturn_t stm32f7_i2c_isr_error(int irq, void *data)
 		f7_msg->result = -EAGAIN;
 	}
 
-	stm32f7_i2c_disable_irq(i2c_dev, STM32F7_I2C_ALL_IRQ_MASK);
+	/* Disable interrupts */
+	if (stm32f7_i2c_is_slave_registered(i2c_dev))
+		mask = STM32F7_I2C_XFER_IRQ_MASK;
+	else
+		mask = STM32F7_I2C_ALL_IRQ_MASK;
+	stm32f7_i2c_disable_irq(i2c_dev, mask);
 
+	i2c_dev->master_mode = false;
 	complete(&i2c_dev->complete);
 
 	return IRQ_HANDLED;
@@ -808,14 +1118,126 @@ static int stm32f7_i2c_xfer(struct i2c_adapter *i2c_adap,
 	return (ret < 0) ? ret : num;
 }
 
+static int stm32f7_i2c_reg_slave(struct i2c_client *slave)
+{
+	struct stm32f7_i2c_dev *i2c_dev = i2c_get_adapdata(slave->adapter);
+	void __iomem *base = i2c_dev->base;
+	struct device *dev = i2c_dev->dev;
+	u32 oar1, oar2, mask;
+	int id, ret;
+
+	if (slave->flags & I2C_CLIENT_PEC) {
+		dev_err(dev, "SMBus PEC not supported in slave mode\n");
+		return -EINVAL;
+	}
+
+	if (stm32f7_i2c_is_slave_busy(i2c_dev)) {
+		dev_err(dev, "Too much slave registered\n");
+		return -EBUSY;
+	}
+
+	ret = stm32f7_i2c_get_free_slave_id(i2c_dev, slave, &id);
+	if (ret)
+		return ret;
+
+	if (!(stm32f7_i2c_is_slave_registered(i2c_dev))) {
+		ret = clk_enable(i2c_dev->clk);
+		if (ret) {
+			dev_err(dev, "Failed to enable clock\n");
+			return ret;
+		}
+	}
+
+	if (id == 0) {
+		/* Configure Own Address 1 */
+		oar1 = readl_relaxed(i2c_dev->base + STM32F7_I2C_OAR1);
+		oar1 &= ~STM32F7_I2C_OAR1_MASK;
+		if (slave->flags & I2C_CLIENT_TEN) {
+			oar1 |= STM32F7_I2C_OAR1_OA1_10(slave->addr);
+			oar1 |= STM32F7_I2C_OAR1_OA1MODE;
+		} else {
+			oar1 |= STM32F7_I2C_OAR1_OA1_7(slave->addr);
+		}
+		oar1 |= STM32F7_I2C_OAR1_OA1EN;
+		i2c_dev->slave[id] = slave;
+		writel_relaxed(oar1, i2c_dev->base + STM32F7_I2C_OAR1);
+	} else if (id == 1) {
+		/* Configure Own Address 2 */
+		oar2 = readl_relaxed(i2c_dev->base + STM32F7_I2C_OAR2);
+		oar2 &= ~STM32F7_I2C_OAR2_MASK;
+		if (slave->flags & I2C_CLIENT_TEN) {
+			ret = -EOPNOTSUPP;
+			goto exit;
+		}
+
+		oar2 |= STM32F7_I2C_OAR2_OA2_7(slave->addr);
+		oar2 |= STM32F7_I2C_OAR2_OA2EN;
+		i2c_dev->slave[id] = slave;
+		writel_relaxed(oar2, i2c_dev->base + STM32F7_I2C_OAR2);
+	} else {
+		ret = -ENODEV;
+		goto exit;
+	}
+
+	/* Enable ACK */
+	stm32f7_i2c_clr_bits(base + STM32F7_I2C_CR2, STM32F7_I2C_CR2_NACK);
+
+	/* Enable Address match interrupt, error interrupt and enable I2C  */
+	mask = STM32F7_I2C_CR1_ADDRIE | STM32F7_I2C_CR1_ERRIE |
+		STM32F7_I2C_CR1_PE;
+	stm32f7_i2c_set_bits(base + STM32F7_I2C_CR1, mask);
+
+	return 0;
+
+exit:
+	if (!(stm32f7_i2c_is_slave_registered(i2c_dev)))
+		clk_disable(i2c_dev->clk);
+
+	return ret;
+}
+
+static int stm32f7_i2c_unreg_slave(struct i2c_client *slave)
+{
+	struct stm32f7_i2c_dev *i2c_dev = i2c_get_adapdata(slave->adapter);
+	void __iomem *base = i2c_dev->base;
+	u32 mask;
+	int id, ret;
+
+	ret = stm32f7_i2c_get_slave_id(i2c_dev, slave, &id);
+	if (ret)
+		return ret;
+
+	WARN_ON(!i2c_dev->slave[id]);
+
+	if (id == 0) {
+		mask = STM32F7_I2C_OAR1_OA1EN;
+		stm32f7_i2c_clr_bits(base + STM32F7_I2C_OAR1, mask);
+	} else {
+		mask = STM32F7_I2C_OAR2_OA2EN;
+		stm32f7_i2c_clr_bits(base + STM32F7_I2C_OAR2, mask);
+	}
+
+	i2c_dev->slave[id] = NULL;
+
+	if (!(stm32f7_i2c_is_slave_registered(i2c_dev))) {
+		stm32f7_i2c_disable_irq(i2c_dev, STM32F7_I2C_ALL_IRQ_MASK);
+		clk_disable(i2c_dev->clk);
+	}
+
+	return 0;
+}
+
 static u32 stm32f7_i2c_func(struct i2c_adapter *adap)
 {
-	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_10BIT_ADDR;
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_10BIT_ADDR |
+		I2C_FUNC_SLAVE;
 }
 
 static struct i2c_algorithm stm32f7_i2c_algo = {
 	.master_xfer = stm32f7_i2c_xfer,
 	.functionality = stm32f7_i2c_func,
+	.reg_slave = stm32f7_i2c_reg_slave,
+	.unreg_slave = stm32f7_i2c_unreg_slave,
 };
 
 static int stm32f7_i2c_probe(struct platform_device *pdev)
-- 
2.7.4