linux-kernel - Re: [PATCH 1/5] dt-bindings: spi: zynqmp-qspi: Add reset

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Message-ID: <50370a62-2e5e-45de-888f-ef3d1bfbb482@linux.dev>
Date: Mon, 27 Jan 2025 13:00:14 -0500
From: Sean Anderson <sean.anderson@...ux.dev>
To: Rob Herring <robh@...nel.org>
Cc: Michal Simek <michal.simek@....com>, Mark Brown <broonie@...nel.org>,
 linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
 Jinjie Ruan <ruanjinjie@...wei.com>, linux-arm-kernel@...ts.infradead.org,
 Amit Kumar Mahapatra <amit.kumar-mahapatra@....com>,
 Miquel Raynal <miquel.raynal@...tlin.com>, Conor Dooley
 <conor+dt@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 devicetree@...r.kernel.org
Subject: Re: [PATCH 1/5] dt-bindings: spi: zynqmp-qspi: Add reset

On 1/27/25 12:57, Rob Herring wrote:
> On Thu, Jan 23, 2025 at 05:57:41PM -0500, Sean Anderson wrote:
>> On 1/23/25 17:45, Rob Herring wrote:
>> > On Fri, Jan 17, 2025 at 11:12:15AM -0500, Sean Anderson wrote:
>> >> On 1/17/25 02:14, Michal Simek wrote:
>> >> > 
>> >> > 
>> >> > On 1/16/25 23:55, Sean Anderson wrote:
>> >> >> Add a reset to help recover from cancelled operations.
>> >> >>
>> >> >> Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>
>> >> >> ---
>> >> >>
>> >> >>   Documentation/devicetree/bindings/spi/spi-zynqmp-qspi.yaml | 6 ++++++
>> >> >>   1 file changed, 6 insertions(+)
>> >> >>
>> >> >> diff --git a/Documentation/devicetree/bindings/spi/spi-zynqmp-qspi.yaml b/Documentation/devicetree/bindings/spi/spi-zynqmp-qspi.yaml
>> >> >> index 04d4d3b4916d..901e15fcce2d 100644
>> >> >> --- a/Documentation/devicetree/bindings/spi/spi-zynqmp-qspi.yaml
>> >> >> +++ b/Documentation/devicetree/bindings/spi/spi-zynqmp-qspi.yaml
>> >> >> @@ -36,12 +36,16 @@ properties:
>> >> >>     power-domains:
>> >> >>       maxItems: 1
>> >> >>   +  resets:
>> >> >> +    maxItems: 1
>> >> >> +
>> >> >>   required:
>> >> >>     - compatible
>> >> >>     - reg
>> >> >>     - interrupts
>> >> >>     - clock-names
>> >> >>     - clocks
>> >> >> +  - resets
>> >> > 
>> >> > In 2/5 you are calling devm_reset_control_get_optional_exclusive() that's why I expect reset is not really required property.
>> >> 
>> >> It's optional for the driver for backwards compatibility. But for the
>> >> devicetree we make it mandatory since it should be included in all new
>> >> devicetrees.
>> > 
>> > Generally, we discourage new required properties as that's an ABI 
>> > change. The exception is really when optional was a mistake. That's 
>> > arguably the case here if the h/w always has a reset.
>> 
>> This device has a reset on ZynqMP and Versal.
>> 
>> The driver still considers this property optional, so it's not an ABI break.
>> But I made it required in the schema to help out the folks at AMD when they
>> get around to upstreaming the Versal devicetree :)
> 
> Not 'the driver', but 'a driver'. You can't say what *all* drivers do. 
> If I write a new driver and read the schema, then I can say 'resets is 
> required so I'll make it required in my new driver'. But then my new 
> driver doesn't work with an older DT that didn't have resets which was 
> valid at the time.

OK, I'll add a description to this effect. The humans can read that, and
the machines won't care.

--Sean