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Message-ID: <5c600a6db6173a56251302da8d2f438435959bd2.camel@gmail.com>
Subject: Re: [PATCH v2 3/3] dt-bindings: adis16460: Add
 'spi-cs-inactive-delay-ns' property
From:   Nuno =?ISO-8859-1?Q?S=E1?= <noname.nuno@gmail.com>
To:     Conor Dooley <conor@kernel.org>
Cc:     Ramona Gradinariu <ramona.gradinariu@analog.com>, jic23@kernel.org,
        nuno.sa@analog.com, robh+dt@kernel.org,
        krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org,
        linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org
Date:   Tue, 24 Oct 2023 08:53:14 +0200
In-Reply-To: <20231023-repost-coma-2f67ea8b95af@spud>
References: <20231023140534.704312-1-ramona.gradinariu@analog.com>
         <20231023140534.704312-4-ramona.gradinariu@analog.com>
         <e97ac024cb2654507ed8f7af715f3604efefbdbb.camel@gmail.com>
         <20231023-repost-coma-2f67ea8b95af@spud>
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On Mon, 2023-10-23 at 17:06 +0100, Conor Dooley wrote:
> On Mon, Oct 23, 2023 at 04:27:48PM +0200, Nuno S=C3=A1 wrote:
> > On Mon, 2023-10-23 at 17:05 +0300, Ramona Gradinariu wrote:
> > > The adis16460 device requires a stall time between SPI
> > > transactions (during which the chip select is inactive),
> > > with a minimum value equal to 16 microseconds.
> > > This commit adds 'spi-cs-inactive-delay-ns' property, which should
> > > indicate the stall time between consecutive SPI transactions.
> > >=20
> > > Signed-off-by: Ramona Gradinariu <ramona.gradinariu@analog.com>
> > > ---
> > > changes in v2:
> > > =C2=A0- added default value
> > > =C2=A0- updated description
> > > =C2=A0- updated commit message
> > > =C2=A0.../devicetree/bindings/iio/imu/adi,adis16460.yaml=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 | 6 ++++++
> > > =C2=A01 file changed, 6 insertions(+)
> > >=20
> > > diff --git a/Documentation/devicetree/bindings/iio/imu/adi,adis16460.=
yaml
> > > b/Documentation/devicetree/bindings/iio/imu/adi,adis16460.yaml
> > > index 4e43c80e5119..f10469b86ee0 100644
> > > --- a/Documentation/devicetree/bindings/iio/imu/adi,adis16460.yaml
> > > +++ b/Documentation/devicetree/bindings/iio/imu/adi,adis16460.yaml
> > > @@ -25,6 +25,12 @@ properties:
> > >=20
> > > =C2=A0=C2=A0 spi-cpol: true
> > >=20
> > > +=C2=A0 spi-cs-inactive-delay-ns:
> > > +=C2=A0=C2=A0=C2=A0 minimum: 16000
> > > +=C2=A0=C2=A0=C2=A0 default: 16000
> > > +=C2=A0=C2=A0=C2=A0 description:
> > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Indicates the stall time between cons=
ecutive SPI transactions.
> > > +
> >=20
> > You should drop the description...=20
> >=20
> > Also, give more time before posting a v2 so others get a chance to revi=
ew
> > your
> > patches. It's also better for you since you can gather more change requ=
ests.
>=20
> Further, I don't see an answer to Krzysztof's question of why the stall
> time would not just be set to 16,000 ns in the driver, based on the
> compatible.

Hi Conor,

Regarding that, I'm the one to blame since I was the one asking for the pro=
perty
during internal review... The reason is that "spi-cs-inactive-delay-ns" is
already part of spi-peripheral-props.yaml which we already reference. So my
question would be why not using it?

These devices are a bit sensitive regarding these timings. Not in devices
supported by this driver but I already experienced having to set timings bi=
gger
than defined in the datasheet for spi to be reliable. this was true on a RP=
I but
might not be in another platform.

Hence having the flexibility to change the time in an already supported pro=
perty
does sound good to me. If not set, we still use the default value based on =
the
compatible. Now, if you tell me "let's just add this if we really get the n=
eed
for it", I get it but I also don't understand why not add it now...

Thanks!
- Nuno S=C3=A1