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SubjectRe: [PATCH v3 5/6] i2c: Add Actions Semiconductor Owl family S900 I2C driver
On Sun, Jul 01, 2018 at 01:43:33PM +0530, Manivannan Sadhasivam wrote:
> Hi Andy,
>
> On Sun, Jul 01, 2018 at 12:11:00AM +0300, Andy Shevchenko wrote:
> > On Sat, Jun 30, 2018 at 4:33 PM, Manivannan Sadhasivam
> > <manivannan.sadhasivam@linaro.org> wrote:
> > > Add Actions Semiconductor Owl family S900 I2C driver.
> >
> > Thanks for an update. Few left comments and it would LGTM.
> >
>
> Thanks :)
>
> > > +static int owl_i2c_reset(struct owl_i2c_dev *i2c_dev)
> > > +{
> >
> > > + mdelay(1);
> >
> > But now, since it's not used in atomic context, we may switch to
> > usleep_range() / msleep() instead.
> >
>
> okay, will use msleep()
>

Just realised, I have to use spinlock for the entire owl_i2c_master_xfer
function, so can't use sleep* for delay.

> > > + owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
> > > + OWL_I2C_CTL_EN, true);
> > > +
> >
> > > + /* Wait 50ms for FIFO reset complete */
> > > + do {
> >
> > > + mdelay(1);
> >
> > Especially in this case it's very important.
> >
>
> Okay.

Same here, but I'm not sure about the latency. What is your suggestion?

Thanks,
Mani

>
> > > + } while (timeout++ < OWL_I2C_MAX_RETRIES);
> >
> > > +}
> >
> > > + val = (i2c_dev->clk_rate + i2c_dev->bus_freq * 16 - 1) /
> > > + (i2c_dev->bus_freq * 16);
> >
> > This is effectively DIV_ROUND_UP(->clk_rate, ->bus_freq * 16).
> >
>
> Ack.
>
> > > + /*
> > > + * By default, 0 will be returned if interrupt occurred but no
> > > + * read or write happened. Else if msg_ptr equals to message length,
> > > + * message count will be returned.
> > > + */
> >
> > > + if (i2c_dev->msg_ptr == msg->len)
> > > + ret = num;
> >
> > I dunno if
> >
> > ret = ->msg_ptr == len ? num : 0;
> >
> > would be slightly more explicit (yes, I aware about ret == 0).
> >
> > Up to you to choose.
> >
>
> As per Peter's comment, returning 0 will get changed to an error value.
> Will use this pattern once we settle with a proper error value.
>
> > > + /* We support only frequencies of 100k and 400k for now */
> > > + if (i2c_dev->bus_freq != OWL_I2C_DEF_SPEED_HZ &&
> > > + i2c_dev->bus_freq > OWL_I2C_MAX_SPEED_HZ) {
> >
> > I think it should be != in the second case as well.
> >
>
> yeah, agree. We don't support any other frequencies now.
>
> Thanks,
> Mani
>
> > > + dev_err(dev, "invalid clock-frequency %d\n", i2c_dev->bus_freq);
> > > + return -EINVAL;
> > > + }
> >
> > --
> > With Best Regards,
> > Andy Shevchenko

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