Re: [PATCH 1/1] i2c: iproc: Add multi byte read-write support for slave mode

[Ray Jui]

Hi Rayagonda,

On 5/8/2019 9:21 PM, Rayagonda Kokatanur wrote:
> Add multiple byte read-write support for slave mode.
> 
> Signed-off-by: Rayagonda Kokatanur <rayagonda.kokatanur@xxxxxxxxxxxx>
> Signed-off-by: Srinath Mannam <srinath.mannam@xxxxxxxxxxxx>
> ---
>  drivers/i2c/busses/i2c-bcm-iproc.c | 117 +++++++++++++++++--------------------
>  1 file changed, 53 insertions(+), 64 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-bcm-iproc.c b/drivers/i2c/busses/i2c-bcm-iproc.c
> index a845b8d..2c7f145 100644
> --- a/drivers/i2c/busses/i2c-bcm-iproc.c
> +++ b/drivers/i2c/busses/i2c-bcm-iproc.c
> @@ -165,12 +165,6 @@ enum i2c_slave_read_status {
>  	I2C_SLAVE_RX_END,
>  };
>  
> -enum i2c_slave_xfer_dir {
> -	I2C_SLAVE_DIR_READ = 0,
> -	I2C_SLAVE_DIR_WRITE,
> -	I2C_SLAVE_DIR_NONE,
> -};
> -
>  enum bus_speed_index {
>  	I2C_SPD_100K = 0,
>  	I2C_SPD_400K,
> @@ -203,7 +197,6 @@ struct bcm_iproc_i2c_dev {
>  	struct i2c_msg *msg;
>  
>  	struct i2c_client *slave;
> -	enum i2c_slave_xfer_dir xfer_dir;
>  
>  	/* bytes that have been transferred */
>  	unsigned int tx_bytes;
> @@ -219,7 +212,8 @@ struct bcm_iproc_i2c_dev {
>  		| BIT(IS_M_RX_THLD_SHIFT))
>  
>  #define ISR_MASK_SLAVE (BIT(IS_S_START_BUSY_SHIFT)\
> -		| BIT(IS_S_RX_EVENT_SHIFT) | BIT(IS_S_RD_EVENT_SHIFT))
> +		| BIT(IS_S_RX_EVENT_SHIFT) | BIT(IS_S_RD_EVENT_SHIFT)\
> +		| BIT(IS_S_TX_UNDERRUN_SHIFT))
>  
>  static int bcm_iproc_i2c_reg_slave(struct i2c_client *slave);
>  static int bcm_iproc_i2c_unreg_slave(struct i2c_client *slave);
> @@ -297,15 +291,11 @@ static void bcm_iproc_i2c_slave_init(
>  	/* clear all pending slave interrupts */
>  	iproc_i2c_wr_reg(iproc_i2c, IS_OFFSET, ISR_MASK_SLAVE);
>  
> -	/* Enable interrupt register for any READ event */
> -	val = BIT(IE_S_RD_EVENT_SHIFT);
>  	/* Enable interrupt register to indicate a valid byte in receive fifo */
> -	val |= BIT(IE_S_RX_EVENT_SHIFT);
> +	val = BIT(IE_S_RX_EVENT_SHIFT);
>  	/* Enable interrupt register for the Slave BUSY command */
>  	val |= BIT(IE_S_START_BUSY_SHIFT);
>  	iproc_i2c_wr_reg(iproc_i2c, IE_OFFSET, val);
> -
> -	iproc_i2c->xfer_dir = I2C_SLAVE_DIR_NONE;
>  }
>  
>  static void bcm_iproc_i2c_check_slave_status(
> @@ -314,8 +304,11 @@ static void bcm_iproc_i2c_check_slave_status(
>  	u32 val;
>  
>  	val = iproc_i2c_rd_reg(iproc_i2c, S_CMD_OFFSET);
> -	val = (val >> S_CMD_STATUS_SHIFT) & S_CMD_STATUS_MASK;
> +	/* status is valid only when START_BUSY is cleared after it was set */
> +	if (val & BIT(S_CMD_START_BUSY_SHIFT))
> +		return;
>  
> +	val = (val >> S_CMD_STATUS_SHIFT) & S_CMD_STATUS_MASK;
>  	if (val == S_CMD_STATUS_TIMEOUT) {
>  		dev_err(iproc_i2c->device, "slave random stretch time timeout\n");
>  
> @@ -327,70 +320,66 @@ static void bcm_iproc_i2c_check_slave_status(
>  }
>  
>  static bool bcm_iproc_i2c_slave_isr(struct bcm_iproc_i2c_dev *iproc_i2c,
> -				u32 status)
> +				    u32 status)
>  {
> -	u8 value;
>  	u32 val;
> -	u32 rd_status;
> -	u32 tmp;
> +	u8 value, rx_status;
>  
> -	/* Start of transaction. check address and populate the direction */
> -	if (iproc_i2c->xfer_dir == I2C_SLAVE_DIR_NONE) {
> -		tmp = iproc_i2c_rd_reg(iproc_i2c, S_RX_OFFSET);
> -		rd_status = (tmp >> S_RX_STATUS_SHIFT) & S_RX_STATUS_MASK;
> -		/* This condition checks whether the request is a new request */
> -		if (((rd_status == I2C_SLAVE_RX_START) &&
> -			(status & BIT(IS_S_RX_EVENT_SHIFT))) ||
> -			((rd_status == I2C_SLAVE_RX_END) &&
> -			(status & BIT(IS_S_RD_EVENT_SHIFT)))) {
> -
> -			/* Last bit is W/R bit.
> -			 * If 1 then its a read request(by master).
> -			 */
> -			iproc_i2c->xfer_dir = tmp & SLAVE_READ_WRITE_BIT_MASK;
> -			if (iproc_i2c->xfer_dir == I2C_SLAVE_DIR_WRITE)
> -				i2c_slave_event(iproc_i2c->slave,
> -					I2C_SLAVE_READ_REQUESTED, &value);
> -			else
> -				i2c_slave_event(iproc_i2c->slave,
> +	/* Slave RX byte receive */
> +	if (status & BIT(IS_S_RX_EVENT_SHIFT)) {
> +		val = iproc_i2c_rd_reg(iproc_i2c, S_RX_OFFSET);
> +		rx_status = (val >> S_RX_STATUS_SHIFT) & S_RX_STATUS_MASK;
> +		if (rx_status == I2C_SLAVE_RX_START) {
> +			/* Start of SMBUS for Master write */
> +			i2c_slave_event(iproc_i2c->slave,
>  					I2C_SLAVE_WRITE_REQUESTED, &value);
> -		}
> -	}
>  
> -	/* read request from master */
> -	if ((status & BIT(IS_S_RD_EVENT_SHIFT)) &&
> -		(iproc_i2c->xfer_dir == I2C_SLAVE_DIR_WRITE)) {
> -		i2c_slave_event(iproc_i2c->slave,
> -			I2C_SLAVE_READ_PROCESSED, &value);
> -		iproc_i2c_wr_reg(iproc_i2c, S_TX_OFFSET, value);
> +			val = iproc_i2c_rd_reg(iproc_i2c, S_RX_OFFSET);
> +			value = (u8)((val >> S_RX_DATA_SHIFT) & S_RX_DATA_MASK);
> +			i2c_slave_event(iproc_i2c->slave,
> +					I2C_SLAVE_WRITE_RECEIVED, &value);
> +		} else if (status & BIT(IS_S_RD_EVENT_SHIFT)) {
> +			/* Start of SMBUS for Master Read */
> +			i2c_slave_event(iproc_i2c->slave,
> +					I2C_SLAVE_READ_REQUESTED, &value);
> +			iproc_i2c_wr_reg(iproc_i2c, S_TX_OFFSET, value);
>  
> -		val = BIT(S_CMD_START_BUSY_SHIFT);
> -		iproc_i2c_wr_reg(iproc_i2c, S_CMD_OFFSET, val);
> -	}
> +			val = BIT(S_CMD_START_BUSY_SHIFT);
> +			iproc_i2c_wr_reg(iproc_i2c, S_CMD_OFFSET, val);
>  
> -	/* write request from master */
> -	if ((status & BIT(IS_S_RX_EVENT_SHIFT)) &&
> -		(iproc_i2c->xfer_dir == I2C_SLAVE_DIR_READ)) {
> -		val = iproc_i2c_rd_reg(iproc_i2c, S_RX_OFFSET);
> -		/* Its a write request by Master to Slave.
> -		 * We read data present in receive FIFO
> -		 */
> -		value = (u8)((val >> S_RX_DATA_SHIFT) & S_RX_DATA_MASK);
> +			/*
> +			 * Enable interrupt for TX FIFO becomes empty and
> +			 * less than PKT_LENGTH bytes were output on the SMBUS
> +			 */
> +			val = iproc_i2c_rd_reg(iproc_i2c, IE_OFFSET);
> +			val |= BIT(IE_S_TX_UNDERRUN_SHIFT);
> +			iproc_i2c_wr_reg(iproc_i2c, IE_OFFSET, val);
> +		} else {
> +			/* Master write other than start */
> +			value = (u8)((val >> S_RX_DATA_SHIFT) & S_RX_DATA_MASK);
> +			i2c_slave_event(iproc_i2c->slave,
> +					I2C_SLAVE_WRITE_RECEIVED, &value);
> +		}
> +	} else if (status & BIT(IS_S_TX_UNDERRUN_SHIFT)) {
> +		/* Master read other than start */
>  		i2c_slave_event(iproc_i2c->slave,
> -			I2C_SLAVE_WRITE_RECEIVED, &value);
> -
> -		/* check the status for the last byte of the transaction */
> -		rd_status = (val >> S_RX_STATUS_SHIFT) & S_RX_STATUS_MASK;
> -		if (rd_status == I2C_SLAVE_RX_END)
> -			iproc_i2c->xfer_dir = I2C_SLAVE_DIR_NONE;
> +				I2C_SLAVE_READ_PROCESSED, &value);
>  
> -		dev_dbg(iproc_i2c->device, "\nread value = 0x%x\n", value);
> +		iproc_i2c_wr_reg(iproc_i2c, S_TX_OFFSET, value);
> +		val = BIT(S_CMD_START_BUSY_SHIFT);
> +		iproc_i2c_wr_reg(iproc_i2c, S_CMD_OFFSET, val);
>  	}
>  
>  	/* Stop */
>  	if (status & BIT(IS_S_START_BUSY_SHIFT)) {
>  		i2c_slave_event(iproc_i2c->slave, I2C_SLAVE_STOP, &value);
> -		iproc_i2c->xfer_dir = I2C_SLAVE_DIR_NONE;
> +		/*
> +		 * Enable interrupt for TX FIFO becomes empty and
> +		 * less than PKT_LENGTH bytes were output on the SMBUS
> +		 */
> +		val = iproc_i2c_rd_reg(iproc_i2c, IE_OFFSET);
> +		val &= ~BIT(IE_S_TX_UNDERRUN_SHIFT);
> +		iproc_i2c_wr_reg(iproc_i2c, IE_OFFSET, val);
>  	}
>  
>  	/* clear interrupt status */
> 

This was already reviewed internally. I just reviewed it again and it
looks fine to me. Thanks.

Reviewed-by: Ray Jui <ray.jui@xxxxxxxxxxxx>