linux-kernel - Re: [PATCH v4] dt-bindings: iio: accel: add binding documentation for ADIS16240

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Message-ID: <a55b9c576eded8c91a985aabbba89180561ab156.camel@analog.com>
Date:   Mon, 25 Nov 2019 07:51:30 +0000
From:   "Ardelean, Alexandru" <alexandru.Ardelean@...log.com>
To:     "jic23@...nel.org" <jic23@...nel.org>,
        "rodrigorsdc@...il.com" <rodrigorsdc@...il.com>
CC:     "Popa, Stefan Serban" <StefanSerban.Popa@...log.com>,
        "kernel-usp@...glegroups.com" <kernel-usp@...glegroups.com>,
        "devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "lars@...afoo.de" <lars@...afoo.de>,
        "pmeerw@...erw.net" <pmeerw@...erw.net>,
        "Hennerich, Michael" <Michael.Hennerich@...log.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "knaack.h@....de" <knaack.h@....de>
Subject: Re: [PATCH v4] dt-bindings: iio: accel: add binding documentation for
 ADIS16240

On Sat, 2019-11-23 at 11:41 +0000, Jonathan Cameron wrote:
> On Sat, 23 Nov 2019 02:19:27 -0300
> Rodrigo Carvalho <rodrigorsdc@...il.com> wrote:
> 
> > This patch add device tree binding documentation for ADIS16240.
> > 
> > Signed-off-by: Rodrigo Ribeiro Carvalho <rodrigorsdc@...il.com>

My bad for the late timing on this.
I'm slightly more fresh on Mondays.
But I will get overloaded with work in a few hours, so I may not have time
ot respond.

> No problem with this patch, but I definitely want to see an accompanying
> one enforcing the SPI mode in the driver.
> 

So, then the binding should probably also define spi-cpol & spi-cpha
as mandatory.
Maybe, the driver would do a check and print a warning.

I'm noticing that this device uses SPI mode 3, but this DT binding defaults
to SPI mode 0

> Right now the driver doesn't set it and so I'm fairly sure not putting
> it in the binding will leave you with a non working device.
> 
> The right option if only one option is supported is for the driver
> to call spi_setup with the relevant options.
> 

What if the board uses some level inverters [because of some weird reason]
and that messes up with the SPI mode?
It's not common, but it is possible.

> Thanks,
> 
> Jonathan
> 
> > ---
> > V4:
> >    - Remove spi-cpha and spi-cpol in binding example, since this driver
> > supports only one timing mode.
> >  .../bindings/iio/accel/adi,adis16240.yaml     | 49 +++++++++++++++++++
> >  1 file changed, 49 insertions(+)
> >  create mode 100644
> > Documentation/devicetree/bindings/iio/accel/adi,adis16240.yaml
> > 
> > diff --git
> > a/Documentation/devicetree/bindings/iio/accel/adi,adis16240.yaml
> > b/Documentation/devicetree/bindings/iio/accel/adi,adis16240.yaml
> > new file mode 100644
> > index 000000000000..8e902f7c49e6
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/iio/accel/adi,adis16240.yaml
> > @@ -0,0 +1,49 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/iio/accel/adi,adis16240.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: ADIS16240 Programmable Impact Sensor and Recorder driver
> > +
> > +maintainers:
> > +  - Alexandru Ardelean <alexandru.ardelean@...log.com>
> > +
> > +description: |
> > +  ADIS16240 Programmable Impact Sensor and Recorder driver that
> > supports
> > +  SPI interface.
> > +    https://www.analog.com/en/products/adis16240.html
> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - adi,adis16240
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  interrupts:
> > +    maxItems: 1
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - interrupts
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/gpio/gpio.h>
> > +    #include <dt-bindings/interrupt-controller/irq.h>
> > +    spi0 {
> > +        #address-cells = <1>;
> > +        #size-cells = <0>;
> > +
> > +        /* Example for a SPI device node */
> > +        accelerometer@0 {
> > +            compatible = "adi,adis16240";
> > +            reg = <0>;
> > +            spi-max-frequency = <2500000>;
> > +            interrupt-parent = <&gpio0>;
> > +            interrupts = <0 IRQ_TYPE_LEVEL_HIGH>;
> > +        };
> > +    };