linux-kernel - RE: [PATCH 3/4] dt-bindings: soc: samsung: exynos-sysreg: add dedicated SYSREG compatibles to Exynos5433

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Date:   Fri, 25 Nov 2022 22:10:40 +0530
From:   "Alim Akhtar" <alim.akhtar@...sung.com>
To:     "'Krzysztof Kozlowski'" <krzysztof.kozlowski@...aro.org>,
        "'Sam Protsenko'" <semen.protsenko@...aro.org>
Cc:     "'Lee Jones'" <lee@...nel.org>,
        "'Rob Herring'" <robh+dt@...nel.org>,
        "'Krzysztof Kozlowski'" <krzysztof.kozlowski+dt@...aro.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-samsung-soc@...r.kernel.org>,
        "'Sriranjani P'" <sriranjani.p@...sung.com>,
        "'Chanho Park'" <chanho61.park@...sung.com>
Subject: RE: [PATCH 3/4] dt-bindings: soc: samsung: exynos-sysreg: add
 dedicated SYSREG compatibles to Exynos5433



>-----Original Message-----
>From: Krzysztof Kozlowski [mailto:krzysztof.kozlowski@...aro.org]
>Sent: Friday, November 25, 2022 8:31 PM
>To: Sam Protsenko <semen.protsenko@...aro.org>
>Cc: Lee Jones <lee@...nel.org>; Rob Herring <robh+dt@...nel.org>;
>Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>; Alim Akhtar
><alim.akhtar@...sung.com>; devicetree@...r.kernel.org; linux-
>kernel@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-
>samsung-soc@...r.kernel.org; Sriranjani P <sriranjani.p@...sung.com>;
>Chanho Park <chanho61.park@...sung.com>
>Subject: Re: [PATCH 3/4] dt-bindings: soc: samsung: exynos-sysreg: add
>dedicated SYSREG compatibles to Exynos5433
>
>On 25/11/2022 15:57, Sam Protsenko wrote:
>> On Fri, 25 Nov 2022 at 08:47, Krzysztof Kozlowski
>> <krzysztof.kozlowski@...aro.org> wrote:
>>>
>>> On 25/11/2022 15:22, Sam Protsenko wrote:
>>>> On Fri, 25 Nov 2022 at 05:22, Krzysztof Kozlowski
>>>> <krzysztof.kozlowski@...aro.org> wrote:
>>>>>
>>>>> Exynos5433 has several different SYSREGs, so use dedicated
>>>>> compatibles for them.
>>>>>
>>>>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>>>>>
>>>>> ---
>>>>>
>>>>> Cc: Sriranjani P <sriranjani.p@...sung.com>
>>>>> Cc: Chanho Park <chanho61.park@...sung.com>
>>>>> Cc: Sam Protsenko <semen.protsenko@...aro.org>
>>>>> ---
>>>>
>>>> Hi Krzysztof,
>>>>
>>>> Just curious: what is the rationale for adding those more specific
>>>> sysregs? AFAIR, e.g. in Exynos850, different SysReg instances have
>>>> pretty much the same register layout.
>>>>
>>>
>>> On Exynos5433 all these blocks have different registers. Are you
>>> saying that Exynos850 has four (or more) sysregs which are exactly the
>same?
>>> Same registers? Why would they duplicate it?
>>>
>>
>> Ah, no, you are right. Just checked it, they are different. Just first
>> couple of registers are similar between blocks, that's why I memorized
>> it wrong.
>>
>> So as I understand, adding those new compatibles follows "describe HW,
>> not a driver" rule? Because AFAIU, right now it'll fallback to
>> "syscon" compatible anyway.
>
>Yes, they describe hardware. Of course all of these sysregs are similar as they
>are just bunch of SFR/MMIO-region, but they have different roles/features.
>For example some other devices (users) of syscon/sysreg should reference
>specific device, not any sysreg.
>
Yes, these are dedicated / extended SFR region to provide IP/Block specific side-band signals / configurations.

>On several other architectures we use specific compatibles, so I think for
>Samsung we should do the same.
>
Yes, most of the SoC's sysreg are dedicated/included in the IP block itself now a day, so make sense to have a dedicated compatible.

>Different case was for Exynos 3/4/5 where there was only one SYSREG.
>
AFAIR, this is correct.

>Best regards,
>Krzysztof