linux-kernel - Re: [PATCH 1/2] dt-bindings: mfd: syscon: Add ti,dss-oldi-io-ctrl compatible

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Message-ID: <1ec72d58-de81-d367-3dc6-900a00b6dac4@ti.com>
Date:   Wed, 9 Aug 2023 12:59:07 -0500
From:   Andrew Davis <afd@...com>
To:     Aradhya Bhatia <a-bhatia1@...com>, Lee Jones <lee@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, Nishanth Menon <nm@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Tero Kristo <kristo@...nel.org>
CC:     <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] dt-bindings: mfd: syscon: Add ti,dss-oldi-io-ctrl
 compatible

On 8/9/23 12:39 PM, Aradhya Bhatia wrote:
> Hi Andrew,
> 
> Thank you for quickly whipping up these patches! =)
> 
> On 09-Aug-23 22:27, Andrew Davis wrote:
>> Add TI DSS OLDI-IO control registers compatible. This is a region of 5
>> 32bit registers found in the TI AM65 CTRL_MMR0 register space[0]. They
>> are used to control the characteristics of the OLDI DATA/CLK IO as needed
>> by the DSS display controller node.
> 
> As long as the driver takes care of it, we can reuse the same compatible
> even when OLDI IO Ctrl registers change from SoC to SoC, (in this case,
> AM65 to AM62), right?
> 

That depends, is the register space still "compatible" with the AM65
version of this space? If not then we would want to qualify these
with their SoC versions.

A quick check of the documentation shows the register space is still
5 registers, 4 DATA and 1 CLK. The contents are different though, but
since this compatible string is not used to match with a driver that
would care (that is handled by the DSS node which does have different
compatibles for each device), I'm actually not sure. Guess we can leave
that decision to the DT binding maintainers..

Andrew

> Regards
> Aradhya
> 
>>
>> [0] https://www.ti.com/lit/pdf/spruid7
>>
>> Signed-off-by: Andrew Davis <afd@...com>
>> ---
>>   Documentation/devicetree/bindings/mfd/syscon.yaml | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/Documentation/devicetree/bindings/mfd/syscon.yaml b/Documentation/devicetree/bindings/mfd/syscon.yaml
>> index 8103154bbb529..5029abd6d6411 100644
>> --- a/Documentation/devicetree/bindings/mfd/syscon.yaml
>> +++ b/Documentation/devicetree/bindings/mfd/syscon.yaml
>> @@ -69,6 +69,7 @@ properties:
>>                 - rockchip,rk3588-qos
>>                 - rockchip,rv1126-qos
>>                 - starfive,jh7100-sysmain
>> +              - ti,dss-oldi-io-ctrl
>>   
>>             - const: syscon
>>