Re: [PATCH v7 5/7] drivers/i2c: Add transfer implementation for FSI algorithm

[Eddie James]

On 05/29/2018 07:08 PM, Andy Shevchenko wrote:
> On Wed, May 30, 2018 at 1:24 AM, Eddie James <eajames@xxxxxxxxxxxxxxxxxx> wrote:
> > From: "Edward A. James" <eajames@xxxxxxxxxx>
> >
> > 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.

Didn't see any other I2C drivers using any helper for msg->flags.

> > +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.

I think it is more readable this way, and I'm not convinced the 
min(rounddown()) is faster. I did however add a common function to do 
this check since it's performed in both the read and write fifo 
functions. Let me know what you think on v8.

Thanks,
Eddie