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SubjectRe: [PATCH v7 5/7] drivers/i2c: Add transfer implementation for FSI algorithm
On Wed, May 30, 2018 at 1:24 AM, Eddie James <eajames@linux.vnet.ibm.com> wrote:
> From: "Edward A. James" <eajames@us.ibm.com>
>
> Execute I2C transfers from the FSI-attached I2C master. Use polling
> instead of interrupts as we have no hardware IRQ over FSI.

> + if (msg->flags & I2C_M_RD)
> + cmd |= I2C_CMD_READ;

I think we have a helper for this, though not sure.

> +static int fsi_i2c_write_fifo(struct fsi_i2c_port *port, struct i2c_msg *msg,
> + u8 fifo_count)
> +{
> + int write;

> + int rc = 0;

Redundant assignment.

> + struct fsi_i2c_master *i2c = port->master;
> + int bytes_to_write = i2c->fifo_size - fifo_count;
> + int bytes_remaining = msg->len - port->xfrd;

> + if (bytes_to_write > bytes_remaining)
> + bytes_to_write = bytes_remaining;

_write = min(_write, _remaining);

> + while (bytes_to_write > 0) {

> + write = bytes_to_write;
> + /* fsi limited to max 4 byte aligned ops */
> + if (bytes_to_write > 4)
> + write = 4;
> + else if (write == 3)
> + write = 2;

write = min_t(int, 4, rounddown_pow_of_two(bytes_to_write));

Also check it carefully, it might be optimized even more, though I
didn't think much.

> + }

> + return rc;

How it can be non-zero?

> +}

> +
> +static int fsi_i2c_read_fifo(struct fsi_i2c_port *port, struct i2c_msg *msg,
> + u8 fifo_count)
> +{
> + int read;

> + int rc = 0;

Redundant assignment.

> + struct fsi_i2c_master *i2c = port->master;
> + int xfr_remaining = msg->len - port->xfrd;
> + u32 dummy;
> +
> + while (fifo_count) {

> + read = fifo_count;
> + /* fsi limited to max 4 byte aligned ops */
> + if (fifo_count > 4)
> + read = 4;
> + else if (read == 3)
> + read = 2;

See above for write case and do in similar way.

> +
> + if (xfr_remaining) {

> + if (xfr_remaining < read)
> + read = xfr_remaining;

read = min(read, _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;
> + }
> +
> + fifo_count -= read;
> + }
> +

> + return rc;

How non-zero possible here?

> +}

> + if (port->xfrd < msg->len)
> + rc = -ENODATA;
> + else
> + rc = msg->len;
> +
> + return rc;

if (...)
return -ENODATA;
return msg->len;
?

> + u32 status = 0;

Redundant assignment.

> + return -ETIME;

ETIMEDOUT ?


--
With Best Regards,
Andy Shevchenko

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