Subject: Re: [PATCH v2] i2c: cadence: Added slave support

From: Wolfram Sang <[email-masked]>
Date: Wed, 15 Apr 2020 14:58:50 +0200

On Mon, Jan 06, 2020 at 12:43:36PM +0200, Radu Pirea wrote:
> Added support for I2C slave functionality
> 
> Signed-off-by: Chirag Parekh <[email-masked]>
> Signed-off-by: Michal Simek <[email-masked]>
> Signed-off-by: Radu Pirea <[email-masked]>

Michal, do you want a second look or is your SoB good as-is?

> ---
> 
> Hi,
> 
> This patch implements the slave interface for the i2c cadence driver. Most of the
> work has been done by the guys from Xilinx. All I have done it was to port the
> patch to the upstream kernel, test it and fix some minor issues.
> 
> Any suggestion about how can I improve this patch is welcome.
> 
> Thanks.
> 
> Radu P.
> 
> Changes in v2:
> - guard id->ctrl_reg_diva_divb with IS_ENABLED(CONFIG_I2C_SLAVE) in 
> cdns_i2c_setclk function
> 
>  drivers/i2c/busses/i2c-cadence.c | 320 +++++++++++++++++++++++++++++--
>  1 file changed, 309 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c
> index 9d71ce15db05..fc5d6bfa6fd5 100644
> --- a/drivers/i2c/busses/i2c-cadence.c
> +++ b/drivers/i2c/busses/i2c-cadence.c
> @@ -23,6 +23,7 @@
>  #define CDNS_I2C_ISR_OFFSET		0x10 /* IRQ Status Register, RW */
>  #define CDNS_I2C_XFER_SIZE_OFFSET	0x14 /* Transfer Size Register, RW */
>  #define CDNS_I2C_TIME_OUT_OFFSET	0x1C /* Time Out Register, RW */
> +#define CDNS_I2C_IMR_OFFSET		0x20 /* IRQ Mask Register, RO */
>  #define CDNS_I2C_IER_OFFSET		0x24 /* IRQ Enable Register, WO */
>  #define CDNS_I2C_IDR_OFFSET		0x28 /* IRQ Disable Register, WO */
>  
> @@ -40,9 +41,17 @@
>  #define CDNS_I2C_CR_DIVB_SHIFT		8
>  #define CDNS_I2C_CR_DIVB_MASK		(0x3f << CDNS_I2C_CR_DIVB_SHIFT)
>  
> +#define CDNS_I2C_CR_MASTER_EN_MASK	(CDNS_I2C_CR_NEA | \
> +					 CDNS_I2C_CR_ACK_EN | \
> +					 CDNS_I2C_CR_MS)
> +
> +#define CDNS_I2C_CR_SLAVE_EN_MASK	~CDNS_I2C_CR_MASTER_EN_MASK
> +
>  /* Status Register Bit mask definitions */
>  #define CDNS_I2C_SR_BA		BIT(8)
> +#define CDNS_I2C_SR_TXDV	BIT(6)
>  #define CDNS_I2C_SR_RXDV	BIT(5)
> +#define CDNS_I2C_SR_RXRW	BIT(3)
>  
>  /*
>   * I2C Address Register Bit mask definitions
> @@ -91,6 +100,14 @@
>  					 CDNS_I2C_IXR_DATA | \
>  					 CDNS_I2C_IXR_COMP)
>  
> +#define CDNS_I2C_IXR_SLAVE_INTR_MASK	(CDNS_I2C_IXR_RX_UNF | \
> +					 CDNS_I2C_IXR_TX_OVF | \
> +					 CDNS_I2C_IXR_RX_OVF | \
> +					 CDNS_I2C_IXR_TO | \
> +					 CDNS_I2C_IXR_NACK | \
> +					 CDNS_I2C_IXR_DATA | \
> +					 CDNS_I2C_IXR_COMP)
> +
>  #define CDNS_I2C_TIMEOUT		msecs_to_jiffies(1000)
>  /* timeout for pm runtime autosuspend */
>  #define CNDS_I2C_PM_TIMEOUT		1000	/* ms */
> @@ -117,6 +134,32 @@
>  #define cdns_i2c_readreg(offset)       readl_relaxed(id->membase + offset)
>  #define cdns_i2c_writereg(val, offset) writel_relaxed(val, id->membase + offset)
>  
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +/**
> + * enum cdns_i2c_mode - I2C Controller current operating mode
> + *
> + * @CDNS_I2C_MODE_SLAVE:       I2C controller operating in slave mode
> + * @CDNS_I2C_MODE_MASTER:      I2C Controller operating in master mode
> + */
> +enum cdns_i2c_mode {
> +	CDNS_I2C_MODE_SLAVE,
> +	CDNS_I2C_MODE_MASTER,
> +};
> +
> +/**
> + * enum cdns_i2c_slave_mode - Slave state when I2C is operating in slave mode
> + *
> + * @CDNS_I2C_SLAVE_STATE_IDLE: I2C slave idle
> + * @CDNS_I2C_SLAVE_STATE_SEND: I2C slave sending data to master
> + * @CDNS_I2C_SLAVE_STATE_RECV: I2C slave receiving data from master
> + */
> +enum cdns_i2c_slave_state {
> +	CDNS_I2C_SLAVE_STATE_IDLE,
> +	CDNS_I2C_SLAVE_STATE_SEND,
> +	CDNS_I2C_SLAVE_STATE_RECV,
> +};
> +#endif
> +
>  /**
>   * struct cdns_i2c - I2C device private data structure
>   *
> @@ -138,6 +181,10 @@
>   * @clk:		Pointer to struct clk
>   * @clk_rate_change_nb:	Notifier block for clock rate changes
>   * @quirks:		flag for broken hold bit usage in r1p10
> + * @ctrl_reg_diva_divb: value of fields DIV_A and DIV_B from CR register
> + * @slave:		Registered slave instance.
> + * @dev_mode:		I2C operating role(master/slave).
> + * @slave_state:	I2C Slave state(idle/read/write).
>   */
>  struct cdns_i2c {
>  	struct device		*dev;
> @@ -158,6 +205,12 @@ struct cdns_i2c {
>  	struct clk *clk;
>  	struct notifier_block clk_rate_change_nb;
>  	u32 quirks;
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +	u16 ctrl_reg_diva_divb;
> +	struct i2c_client *slave;
> +	enum cdns_i2c_mode dev_mode;
> +	enum cdns_i2c_slave_state slave_state;
> +#endif
>  };
>  
>  struct cdns_platform_data {
> @@ -186,17 +239,155 @@ static inline bool cdns_is_holdquirk(struct cdns_i2c *id, bool hold_wrkaround)
>  		(id->curr_recv_count == CDNS_I2C_FIFO_DEPTH + 1));
>  }
>  
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +static void cdns_i2c_set_mode(enum cdns_i2c_mode mode, struct cdns_i2c *id)
> +{
> +	/* Disable all interrupts */
> +	cdns_i2c_writereg(CDNS_I2C_IXR_ALL_INTR_MASK, CDNS_I2C_IDR_OFFSET);
> +
> +	/* Clear FIFO and transfer size */
> +	cdns_i2c_writereg(CDNS_I2C_CR_CLR_FIFO, CDNS_I2C_CR_OFFSET);
> +
> +	/* Update device mode and state */
> +	id->dev_mode = mode;
> +	id->slave_state = CDNS_I2C_SLAVE_STATE_IDLE;
> +
> +	switch (mode) {
> +	case CDNS_I2C_MODE_MASTER:
> +		/* Enable i2c master */
> +		cdns_i2c_writereg(id->ctrl_reg_diva_divb |
> +				  CDNS_I2C_CR_MASTER_EN_MASK,
> +				  CDNS_I2C_CR_OFFSET);
> +		/*
> +		 * This delay is needed to give the IP some time to switch to
> +		 * the master mode. With lower values(like 110 us) i2cdetect
> +		 * will not detect any slave and without this delay, the IP will
> +		 * trigger a timeout interrupt.
> +		 */
> +		usleep_range(115, 125);
> +		break;
> +	case CDNS_I2C_MODE_SLAVE:
> +		/* Enable i2c slave */
> +		cdns_i2c_writereg(id->ctrl_reg_diva_divb &
> +				  CDNS_I2C_CR_SLAVE_EN_MASK,
> +				  CDNS_I2C_CR_OFFSET);
> +
> +		/* Setting slave address */
> +		cdns_i2c_writereg(id->slave->addr & CDNS_I2C_ADDR_MASK,
> +				  CDNS_I2C_ADDR_OFFSET);
> +
> +		/* Enable slave send/receive interrupts */
> +		cdns_i2c_writereg(CDNS_I2C_IXR_SLAVE_INTR_MASK,
> +				  CDNS_I2C_IER_OFFSET);
> +		break;
> +	}
> +}
> +
> +static void cdns_i2c_slave_rcv_data(struct cdns_i2c *id)
> +{
> +	u8 bytes;
> +	unsigned char data;
> +
> +	/* Prepare backend for data reception */
> +	if (id->slave_state == CDNS_I2C_SLAVE_STATE_IDLE) {
> +		id->slave_state = CDNS_I2C_SLAVE_STATE_RECV;
> +		i2c_slave_event(id->slave, I2C_SLAVE_WRITE_REQUESTED, NULL);
> +	}
> +
> +	/* Fetch number of bytes to receive */
> +	bytes = cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET);
> +
> +	/* Read data and send to backend */
> +	while (bytes--) {
> +		data = cdns_i2c_readreg(CDNS_I2C_DATA_OFFSET);
> +		i2c_slave_event(id->slave, I2C_SLAVE_WRITE_RECEIVED, &data);
> +	}
> +}
> +
> +static void cdns_i2c_slave_send_data(struct cdns_i2c *id)
> +{
> +	u8 data;
> +
> +	/* Prepare backend for data transmission */
> +	if (id->slave_state == CDNS_I2C_SLAVE_STATE_IDLE) {
> +		id->slave_state = CDNS_I2C_SLAVE_STATE_SEND;
> +		i2c_slave_event(id->slave, I2C_SLAVE_READ_REQUESTED, &data);
> +	} else {
> +		i2c_slave_event(id->slave, I2C_SLAVE_READ_PROCESSED, &data);
> +	}
> +
> +	/* Send data over bus */
> +	cdns_i2c_writereg(data, CDNS_I2C_DATA_OFFSET);
> +}
> +
>  /**
> - * cdns_i2c_isr - Interrupt handler for the I2C device
> - * @irq:	irq number for the I2C device
> - * @ptr:	void pointer to cdns_i2c structure
> + * cdns_i2c_slave_isr - Interrupt handler for the I2C device in slave role
> + * @ptr:       Pointer to I2C device private data
> + *
> + * This function handles the data interrupt and transfer complete interrupt of
> + * the I2C device in slave role.
> + *
> + * Return: IRQ_HANDLED always
> + */
> +static irqreturn_t cdns_i2c_slave_isr(void *ptr)
> +{
> +	struct cdns_i2c *id = ptr;
> +	unsigned int isr_status, i2c_status;
> +
> +	/* Fetch the interrupt status */
> +	isr_status = cdns_i2c_readreg(CDNS_I2C_ISR_OFFSET);
> +	cdns_i2c_writereg(isr_status, CDNS_I2C_ISR_OFFSET);
> +
> +	/* Ignore masked interrupts */
> +	isr_status &= ~cdns_i2c_readreg(CDNS_I2C_IMR_OFFSET);
> +
> +	/* Fetch transfer mode (send/receive) */
> +	i2c_status = cdns_i2c_readreg(CDNS_I2C_SR_OFFSET);
> +
> +	/* Handle data send/receive */
> +	if (i2c_status & CDNS_I2C_SR_RXRW) {
> +		/* Send data to master */
> +		if (isr_status & CDNS_I2C_IXR_DATA)
> +			cdns_i2c_slave_send_data(id);
> +
> +		if (isr_status & CDNS_I2C_IXR_COMP) {
> +			id->slave_state = CDNS_I2C_SLAVE_STATE_IDLE;
> +			i2c_slave_event(id->slave, I2C_SLAVE_STOP, NULL);
> +		}
> +	} else {
> +		/* Receive data from master */
> +		if (isr_status & CDNS_I2C_IXR_DATA)
> +			cdns_i2c_slave_rcv_data(id);
> +
> +		if (isr_status & CDNS_I2C_IXR_COMP) {
> +			cdns_i2c_slave_rcv_data(id);
> +			id->slave_state = CDNS_I2C_SLAVE_STATE_IDLE;
> +			i2c_slave_event(id->slave, I2C_SLAVE_STOP, NULL);
> +		}
> +	}
> +
> +	/* Master indicated xfer stop or fifo underflow/overflow */
> +	if (isr_status & (CDNS_I2C_IXR_NACK | CDNS_I2C_IXR_RX_OVF |
> +			  CDNS_I2C_IXR_RX_UNF | CDNS_I2C_IXR_TX_OVF)) {
> +		id->slave_state = CDNS_I2C_SLAVE_STATE_IDLE;
> +		i2c_slave_event(id->slave, I2C_SLAVE_STOP, NULL);
> +		cdns_i2c_writereg(CDNS_I2C_CR_CLR_FIFO, CDNS_I2C_CR_OFFSET);
> +	}
> +
> +	return IRQ_HANDLED;
> +}
> +#endif
> +
> +/**
> + * cdns_i2c_master_isr - Interrupt handler for the I2C device in master role
> + * @ptr:       Pointer to I2C device private data
>   *
>   * This function handles the data interrupt, transfer complete interrupt and
> - * the error interrupts of the I2C device.
> + * the error interrupts of the I2C device in master role.
>   *
>   * Return: IRQ_HANDLED always
>   */
> -static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
> +static irqreturn_t cdns_i2c_master_isr(void *ptr)
>  {
>  	unsigned int isr_status, avail_bytes, updatetx;
>  	unsigned int bytes_to_send;
> @@ -352,6 +543,27 @@ static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
>  	return status;
>  }
>  
> +/**
> + * cdns_i2c_isr - Interrupt handler for the I2C device
> + * @irq:	irq number for the I2C device
> + * @ptr:	void pointer to cdns_i2c structure
> + *
> + * This function passes the control to slave/master based on current role of
> + * i2c controller.
> + *
> + * Return: IRQ_HANDLED always
> + */
> +static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
> +{
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +	struct cdns_i2c *id = ptr;
> +
> +	if (id->dev_mode == CDNS_I2C_MODE_SLAVE)
> +		return cdns_i2c_slave_isr(ptr);
> +#endif
> +	return cdns_i2c_master_isr(ptr);
> +}
> +
>  /**
>   * cdns_i2c_mrecv - Prepare and start a master receive operation
>   * @id:		pointer to the i2c device structure
> @@ -572,10 +784,28 @@ static int cdns_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
>  	u32 reg;
>  	struct cdns_i2c *id = adap->algo_data;
>  	bool hold_quirk;
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +	bool change_role = false;
> +#endif
>  
>  	ret = pm_runtime_get_sync(id->dev);
>  	if (ret < 0)
>  		return ret;
> +
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +	/* Check i2c operating mode and switch if possible */
> +	if (id->dev_mode == CDNS_I2C_MODE_SLAVE) {
> +		if (id->slave_state != CDNS_I2C_SLAVE_STATE_IDLE)
> +			return -EAGAIN;
> +
> +		/* Set mode to master */
> +		cdns_i2c_set_mode(CDNS_I2C_MODE_MASTER, id);
> +
> +		/* Mark flag to change role once xfer is completed */
> +		change_role = true;
> +	}
> +#endif
> +
>  	/* Check if the bus is free */
>  	if (cdns_i2c_readreg(CDNS_I2C_SR_OFFSET) & CDNS_I2C_SR_BA) {
>  		ret = -EAGAIN;
> @@ -634,7 +864,15 @@ static int cdns_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
>  	}
>  
>  	ret = num;
> +
>  out:
> +
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +	/* Switch i2c mode to slave */
> +	if (change_role)
> +		cdns_i2c_set_mode(CDNS_I2C_MODE_SLAVE, id);
> +#endif
> +
>  	pm_runtime_mark_last_busy(id->dev);
>  	pm_runtime_put_autosuspend(id->dev);
>  	return ret;
> @@ -648,14 +886,67 @@ static int cdns_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
>   */
>  static u32 cdns_i2c_func(struct i2c_adapter *adap)
>  {
> -	return I2C_FUNC_I2C | I2C_FUNC_10BIT_ADDR |
> -		(I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK) |
> -		I2C_FUNC_SMBUS_BLOCK_DATA;
> +	u32 func = I2C_FUNC_I2C | I2C_FUNC_10BIT_ADDR |
> +			(I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK) |
> +			I2C_FUNC_SMBUS_BLOCK_DATA;
> +
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +	func |= I2C_FUNC_SLAVE;
> +#endif
> +
> +	return func;
>  }
>  
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +static int cdns_reg_slave(struct i2c_client *slave)
> +{
> +	int ret;
> +	struct cdns_i2c *id = container_of(slave->adapter, struct cdns_i2c,
> +									adap);
> +
> +	if (id->slave)
> +		return -EBUSY;
> +
> +	if (slave->flags & I2C_CLIENT_TEN)
> +		return -EAFNOSUPPORT;
> +
> +	ret = pm_runtime_get_sync(id->dev);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Store slave information */
> +	id->slave = slave;
> +
> +	/* Enable I2C slave */
> +	cdns_i2c_set_mode(CDNS_I2C_MODE_SLAVE, id);
> +
> +	return 0;
> +}
> +
> +static int cdns_unreg_slave(struct i2c_client *slave)
> +{
> +	struct cdns_i2c *id = container_of(slave->adapter, struct cdns_i2c,
> +									adap);
> +
> +	pm_runtime_put(id->dev);
> +
> +	/* Remove slave information */
> +	id->slave = NULL;
> +
> +	/* Enable I2C master */
> +	cdns_i2c_set_mode(CDNS_I2C_MODE_MASTER, id);
> +
> +	return 0;
> +}
> +#endif
> +
>  static const struct i2c_algorithm cdns_i2c_algo = {
>  	.master_xfer	= cdns_i2c_master_xfer,
>  	.functionality	= cdns_i2c_func,
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +	.reg_slave	= cdns_reg_slave,
> +	.unreg_slave	= cdns_unreg_slave,
> +#endif
>  };
>  
>  /**
> @@ -750,7 +1041,10 @@ static int cdns_i2c_setclk(unsigned long clk_in, struct cdns_i2c *id)
>  	ctrl_reg |= ((div_a << CDNS_I2C_CR_DIVA_SHIFT) |
>  			(div_b << CDNS_I2C_CR_DIVB_SHIFT));
>  	cdns_i2c_writereg(ctrl_reg, CDNS_I2C_CR_OFFSET);
> -
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +	id->ctrl_reg_diva_divb = ctrl_reg & (CDNS_I2C_CR_DIVA_MASK |
> +				 CDNS_I2C_CR_DIVB_MASK);
> +#endif
>  	return 0;
>  }
>  
> @@ -943,8 +1237,12 @@ static int cdns_i2c_probe(struct platform_device *pdev)
>  	if (ret || (id->i2c_clk > CDNS_I2C_SPEED_MAX))
>  		id->i2c_clk = CDNS_I2C_SPEED_DEFAULT;
>  
> -	cdns_i2c_writereg(CDNS_I2C_CR_ACK_EN | CDNS_I2C_CR_NEA | CDNS_I2C_CR_MS,
> -			  CDNS_I2C_CR_OFFSET);
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +	/* Set initial mode to master */
> +	id->dev_mode = CDNS_I2C_MODE_MASTER;
> +	id->slave_state = CDNS_I2C_SLAVE_STATE_IDLE;
> +#endif
> +	cdns_i2c_writereg(CDNS_I2C_CR_MASTER_EN_MASK, CDNS_I2C_CR_OFFSET);
>  
>  	ret = cdns_i2c_setclk(id->input_clk, id);
>  	if (ret) {
> -- 
> 2.24.1
> 
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