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Subject: Re: [PATCH v9 5/7] i2c: fsi: Add transfer implementation
To:     Eddie James <eajames@linux.vnet.ibm.com>, linux-i2c@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
        wsa@the-dreams.de, robh+dt@kernel.org, benh@kernel.crashing.org,
        joel@jms.id.au, mark.rutland@arm.com, gregkh@linuxfoundation.org,
        rdunlap@infradead.org, andy.shevchenko@gmail.com
References: <1528138850-18259-1-git-send-email-eajames@linux.vnet.ibm.com>
 <1528138850-18259-6-git-send-email-eajames@linux.vnet.ibm.com>
From:   Peter Rosin <peda@axentia.se>
Organization: Axentia Technologies AB
Message-ID: <92b61473-b5bb-ea2e-56ce-5375641c5242@axentia.se>
Date:   Mon, 4 Jun 2018 21:45:31 +0200
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On 2018-06-04 21:00, Eddie James wrote:
> Execute I2C transfers from the FSI-attached I2C master. Use polling
> instead of interrupts as we have no hardware IRQ over FSI.
> 
> Signed-off-by: Eddie James <eajames@linux.vnet.ibm.com>
> ---
>  drivers/i2c/busses/i2c-fsi.c | 195 ++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 193 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-fsi.c b/drivers/i2c/busses/i2c-fsi.c
> index 101b9c5..4e5964e 100644
> --- a/drivers/i2c/busses/i2c-fsi.c
> +++ b/drivers/i2c/busses/i2c-fsi.c
> @@ -150,6 +150,7 @@ struct fsi_i2c_port {
>  	struct i2c_adapter	adapter;
>  	struct fsi_i2c_master	*master;
>  	u16			port;
> +	u16			xfrd;
>  };
>  
>  static int fsi_i2c_read_reg(struct fsi_device *fsi, unsigned int reg,
> @@ -225,6 +226,99 @@ static int fsi_i2c_set_port(struct fsi_i2c_port *port)
>  	return fsi_i2c_write_reg(fsi, I2C_FSI_RESET_ERR, &dummy);
>  }
>  
> +static int fsi_i2c_start(struct fsi_i2c_port *port, struct i2c_msg *msg,
> +			 bool stop)
> +{
> +	struct fsi_i2c_master *i2c = port->master;
> +	u32 cmd = I2C_CMD_WITH_START | I2C_CMD_WITH_ADDR;
> +
> +	port->xfrd = 0;
> +
> +	if (msg->flags & I2C_M_RD)
> +		cmd |= I2C_CMD_READ;
> +
> +	if (stop || msg->flags & I2C_M_STOP)
> +		cmd |= I2C_CMD_WITH_STOP;
> +
> +	cmd |= FIELD_PREP(I2C_CMD_ADDR, msg->addr >> 1);
> +	cmd |= FIELD_PREP(I2C_CMD_LEN, msg->len);
> +
> +	return fsi_i2c_write_reg(i2c->fsi, I2C_FSI_CMD, &cmd);
> +}
> +
> +static int fsi_i2c_get_op_bytes(int op_bytes)
> +{
> +	/* fsi is limited to max 4 byte aligned ops */
> +	if (op_bytes > 4)
> +		return 4;
> +	else if (op_bytes == 3)
> +		return 2;
> +	return op_bytes;
> +}
> +
> +static int fsi_i2c_write_fifo(struct fsi_i2c_port *port, struct i2c_msg *msg,
> +			      u8 fifo_count)
> +{
> +	int write;
> +	int rc;
> +	struct fsi_i2c_master *i2c = port->master;
> +	int bytes_to_write = i2c->fifo_size - fifo_count;
> +	int bytes_remaining = msg->len - port->xfrd;
> +
> +	bytes_to_write = min(bytes_to_write, bytes_remaining);
> +
> +	while (bytes_to_write) {
> +		write = fsi_i2c_get_op_bytes(bytes_to_write);
> +
> +		rc = fsi_device_write(i2c->fsi, I2C_FSI_FIFO,
> +				      &msg->buf[port->xfrd], write);
> +		if (rc)
> +			return rc;
> +
> +		port->xfrd += write;
> +		bytes_to_write -= write;
> +	}
> +
> +	return 0;
> +}
> +
> +static int fsi_i2c_read_fifo(struct fsi_i2c_port *port, struct i2c_msg *msg,
> +			     u8 fifo_count)
> +{
> +	int read;
> +	int rc;
> +	struct fsi_i2c_master *i2c = port->master;
> +	int bytes_to_read;
> +	int xfr_remaining = msg->len - port->xfrd;
> +	u32 dummy;
> +
> +	bytes_to_read = min_t(int, fifo_count, xfr_remaining);
> +
> +	while (bytes_to_read) {
> +		read = fsi_i2c_get_op_bytes(bytes_to_read);
> +
> +		if (xfr_remaining) {
> +			rc = fsi_device_read(i2c->fsi, I2C_FSI_FIFO,
> +					     &msg->buf[port->xfrd], read);
> +			if (rc)
> +				return rc;
> +
> +			port->xfrd += read;
> +			xfr_remaining -= read;
> +		} else {
> +			/* no more buffer but data in fifo, need to clear it */
> +			rc = fsi_device_read(i2c->fsi, I2C_FSI_FIFO, &dummy,
> +					     read);
> +			if (rc)
> +				return rc;
> +		}
> +
> +		bytes_to_read -= read;
> +	}
> +
> +	return 0;
> +}
> +
>  static int fsi_i2c_reset_bus(struct fsi_i2c_master *i2c)
>  {
>  	int i, rc;
> @@ -388,17 +482,114 @@ static int fsi_i2c_abort(struct fsi_i2c_port *port, u32 status)
>  	return -ETIMEDOUT;
>  }
>  
> +static int fsi_i2c_handle_status(struct fsi_i2c_port *port,
> +				 struct i2c_msg *msg, u32 status)
> +{
> +	int rc;
> +	u8 fifo_count;
> +
> +	if (status & I2C_STAT_ERR) {
> +		rc = fsi_i2c_abort(port, status);
> +		if (rc)
> +			return rc;
> +
> +		if (status & I2C_STAT_INV_CMD)
> +			return -EINVAL;
> +
> +		if (status & (I2C_STAT_PARITY | I2C_STAT_BE_OVERRUN |
> +		    I2C_STAT_BE_ACCESS))
> +			return -EPROTO;
> +
> +		if (status & I2C_STAT_NACK)
> +			return -ENXIO;
> +
> +		if (status & I2C_STAT_LOST_ARB)
> +			return -EAGAIN;
> +
> +		if (status & I2C_STAT_STOP_ERR)
> +			return -EBADMSG;
> +
> +		return -EIO;
> +	}
> +
> +	if (status & I2C_STAT_DAT_REQ) {
> +		fifo_count = FIELD_GET(I2C_STAT_FIFO_COUNT, status);
> +
> +		if (msg->flags & I2C_M_RD)
> +			return fsi_i2c_read_fifo(port, msg, fifo_count);
> +
> +		return fsi_i2c_write_fifo(port, msg, fifo_count);
> +	}
> +
> +	if (status & I2C_STAT_CMD_COMP) {
> +		if (port->xfrd < msg->len)
> +			return -ENODATA;
> +
> +		return msg->len;
> +	}
> +
> +	return 0;
> +}
> +
> +static int fsi_i2c_wait(struct fsi_i2c_port *port, struct i2c_msg *msg,
> +			unsigned long timeout)
> +{
> +	u32 status = 0;
> +	int rc;
> +	unsigned long start = jiffies;
> +
> +	do {
> +		rc = fsi_i2c_read_reg(port->master->fsi, I2C_FSI_STAT,
> +				      &status);
> +		if (rc)
> +			return rc;
> +
> +		if (status & I2C_STAT_ANY_RESP) {
> +			rc = fsi_i2c_handle_status(port, msg, status);
> +			if (rc < 0)
> +				return rc;
> +
> +			/* cmd complete and all data xfrd */
> +			if (rc == msg->len)
> +				return 0;
> +
> +			/* need to xfr more data, but maybe don't need wait */
> +			continue;
> +		}
> +
> +		usleep_range(I2C_CMD_SLEEP_MIN_US, I2C_CMD_SLEEP_MAX_US);
> +	} while (time_after(start + timeout, jiffies));
> +
> +	return -ETIMEDOUT;
> +}
> +
>  static int fsi_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
>  			int num)
>  {
> -	int rc;
> +	int i, rc;
> +	unsigned long start_time;
>  	struct fsi_i2c_port *port = adap->algo_data;
> +	struct i2c_msg *msg;
>  
>  	rc = fsi_i2c_set_port(port);
>  	if (rc)
>  		return rc;
>  
> -	return -EOPNOTSUPP;
> +	for (i = 0; i < num; i++) {
> +		msg = msgs + i;
> +		start_time = jiffies;
> +
> +		rc = fsi_i2c_start(port, msg, i == num - 1);
> +		if (rc)
> +			return rc;
> +
> +		rc = fsi_i2c_wait(port, msg,
> +				  adap->timeout - (jiffies - start_time));
> +		if (rc)
> +			return rc;
> +	}
> +
> +	return 0;

Zero is not the return value of success for .master_xfer

Hint, "num" is your friend...

Cheers,
Peter

>  }
>  
>  static u32 fsi_i2c_functionality(struct i2c_adapter *adap)
>