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

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Message-ID: <CY4PR03MB339939479450FC5F3E8172D39BE29@CY4PR03MB3399.namprd03.prod.outlook.com>
Date:   Tue, 20 Jul 2021 14:33:10 +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

> -----Original Message-----
> From: Andy Shevchenko <andy.shevchenko@...il.com>
> Sent: Tuesday, July 20, 2021 5:08 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 Tue, Jul 20, 2021 at 4:17 PM Miclaus, Antoniu
> <Antoniu.Miclaus@...log.com> wrote:
> > > From: Andy Shevchenko <andy.shevchenko@...il.com>
> > > Sent: Friday, July 16, 2021 5:53 PM
> > > On Fri, Jul 16, 2021 at 2:43 PM Antoniu Miclaus
> > > <antoniu.miclaus@...log.com> wrote:
> 
> ...
> 
> > > 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://urldefense.com/v3/__https://github.com/torvalds/linux/commit/41
> 91f19792bf91267835eb090d970e9cd6277a65__;!!A3Ni8CS0y2Y!ptUV0YC2nfD
> 6AdH_y5U0ziyELl4B9pDL0ubkdpFHFtrFNE_NqUS_TWm_gE-SlHV315Ak$
> > 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.
> 
> Not sure I follow you. That patch is upstream. Does it prevent you
> from switching to regmap SPI API?

It does not prevent me from switching to regmap SPI API.
It will prevent me from using regmap_read to read directly from device.
https://github.com/torvalds/linux/commit/4191f19792bf91267835eb090d970e9cd6277a65#diff-3e0b7d2f0a55adb6573693a514cb8024a81a55da848cb22632ab5fd4dd6dd4e4R39

> 
> ...
> 
> > > > +        depends on COMMON_CLK
> > >
> > > Is it mandatory for any function inside the device?
> >
> > Yes. It will serve as LO input to the device.
> 
> But can the device work without it (with limited functionality)?
This aspect is not clearly stated in the datasheet, but since the Enable register has the LO enabled by default, I considered this aspect as being mandatory.
I will try to find out more information from the hardware guys who developed the part.

> 
> --
> With Best Regards,
> Andy Shevchenko