linux-kernel - Re: [PATCH 1/4] dt-bindings: spi: amlogic,a1-spifc: make power-domains required

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Message-ID: <fde4a6be-6c6b-4275-a320-85e43f62bddd@linaro.org>
Date: Wed, 10 Jul 2024 18:38:33 +0200
From: neil.armstrong@...aro.org
To: George Stark <gnstark@...utedevices.com>,
 Krzysztof Kozlowski <krzk@...nel.org>, robh@...nel.org
Cc: linux-i2c@...r.kernel.org, linux-spi@...r.kernel.org, krzk+dt@...nel.org,
 hkallweit1@...il.com, glaroque@...libre.com, khilman@...libre.com,
 broonie@...nel.org, jbrunet@...libre.com,
 martin.blumenstingl@...glemail.com, linux-pm@...r.kernel.org,
 devicetree@...r.kernel.org, linux-amlogic@...ts.infradead.org,
 lukasz.luba@....com, b.galvani@...il.com, mmkurbanov@...rdevices.ru,
 rui.zhang@...el.com, rafael@...nel.org, daniel.lezcano@...aro.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 kernel@...utedevices.com, conor+dt@...nel.org
Subject: Re: [PATCH 1/4] dt-bindings: spi: amlogic,a1-spifc: make
 power-domains required

On 10/07/2024 18:23, George Stark wrote:
> Hello Krzysztof, Neil, Rob
> 
> Thanks for your reviews.
> 
> I'd just like to clarify things a little on that matter. On A1 most of
> periphery has either dedicated power domain (ir, spifc, spi, cpu etc) or
> several peripheries share single PD e.g. pwm, temp sensor, i2c, adc
> share PD 12. Appropriate PD must be turned on before the periphery is
> touched and be on while periphery is used. Experiments confirm it. So
> power-domains property in dts nodes is really required. It makes kernel
> to control PDs when bound periphery is used.
> 
> If I understand bindings thing correctly we should make power-domains
> property required in bindings too in that case, at least for those
> peripheries which has *a1* compatibles (some peripheries use compatible
> from older SoCs without PDs).
> 
> What you think?

Yes, but if the compatible has already been defined without a required
power-domain, then it's too late to mark it as required since it's an ABI
break.

So next time a new compatible is added, it's the appropriate time to mark
it as required.

But in any case it's not a big deal because if the power-domain is not
specified it won't work, like if you use wrong register address or the
wrong interrupt line.

The fact power-domain can be specified is enough.

Neil

> 
> On 7/8/24 22:51, Krzysztof Kozlowski wrote:
>> On 08/07/2024 21:48, George Stark wrote:
>>> SPI Flash Controller has dedicated power domain so make the
>>> corresponding property required.
>>
>> That's an ABI break. Being part of power domain does not necessarily
>> mean it must be required, so your commit msg lacks rationale. Especially
>> on the ABI part.
>>
>>
>>
>> Best regards,
>> Krzysztof
>>
>