linux-kernel - RE: [PATCH v6 1/2] iio: frequency: adrf6780: add support for ADRF6780

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Date:   Tue, 20 Jul 2021 13:17:46 +0000
From:   "Miclaus, Antoniu" <Antoniu.Miclaus@...log.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
CC:     "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jic23@...nel.org" <jic23@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: RE: [PATCH v6 1/2] iio: frequency: adrf6780: add support for ADRF6780

Hello Andy,

Thanks for the review:

> -----Original Message-----
> From: Andy Shevchenko <andy.shevchenko@...il.com>
> Sent: Friday, July 16, 2021 5:53 PM
> To: Miclaus, Antoniu <Antoniu.Miclaus@...log.com>
> Cc: linux-iio@...r.kernel.org; linux-kernel@...r.kernel.org;
> jic23@...nel.org; devicetree@...r.kernel.org
> Subject: Re: [PATCH v6 1/2] iio: frequency: adrf6780: add support for
> ADRF6780
> 
> [External]
> 
> On Fri, Jul 16, 2021 at 2:43 PM Antoniu Miclaus
> <antoniu.miclaus@...log.com> wrote:
> >
> > The ADRF6780 is a silicon germanium (SiGe) design, wideband,
> > microwave upconverter optimized for point to point microwave
> > radio designs operating in the 5.9 GHz to 23.6 GHz frequency
> > range.
> 
> > Datasheet:
> > https://www.analog.com/media/en/technical-documentation/data-
> sheets/ADRF6780.pdf
> 
> Is it one line? If not, please put on one line and drop below the
> blank line so it will go as a tag.
Yes, it is one line.
> 
> >
> > Signed-off-by: Antoniu Miclaus <antoniu.miclaus@...log.com>
> 
> First question is why not to use the regmap API (I have heard it has
> gained support of 17 bit)?

Initially that was the plan, but after this patch:
https://github.com/torvalds/linux/commit/4191f19792bf91267835eb090d970e9cd6277a65
the custom write formats for regmap allow the read only via cached registers.

Therefore, I preferred using spi transfers for write/read to/from the device.
> ...
> 
> > +        depends on COMMON_CLK
> 
> Is it mandatory for any function inside the device?

Yes. It will serve as LO input to the device.
> 
> ...
> 
> > +static int adrf6780_spi_read(struct adrf6780_dev *dev, unsigned int reg,
> > +                             unsigned int *val)
> > +{
> > +       int ret;
> > +       struct spi_transfer t = {0};
> 
> > +       dev->data[0] = 0x80 | (reg << 1);
> 
> This 0x80 I guess is pretty much standard and regmap SPI supports it.
> 
> > +       dev->data[1] = 0x0;
> > +       dev->data[2] = 0x0;
> > +
> > +       t.rx_buf = &dev->data[0];
> > +       t.tx_buf = &dev->data[0];
> > +       t.len = 3;
> > +
> > +       ret = spi_sync_transfer(dev->spi, &t, 1);
> > +       if (ret)
> > +               return ret;
> > +
> > +       *val = (get_unaligned_be24(&dev->data[0]) >> 1) & GENMASK(15, 0);
> > +
> > +       return ret;
> > +}
> 
> ...
> 
> > +       usleep_range(200, 250);
> 
> Needs a comment.
Will add in next patch version.
> 
> --
> With Best Regards,
> Andy Shevchenko

Regards,
Antoniu