linux-kernel - Re: [PATCH 10/11] arm64: dts: exynos: gs101: add the chipid node

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Message-ID: <3a2f9b58-bbdf-4977-b06b-9f43a4555274@linaro.org>
Date: Mon, 10 Nov 2025 11:28:57 +0200
From: Tudor Ambarus <tudor.ambarus@...aro.org>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Alim Akhtar <alim.akhtar@...sung.com>,
 Peter Griffin <peter.griffin@...aro.org>,
 André Draszik <andre.draszik@...aro.org>,
 semen.protsenko@...aro.org, willmcvicker@...gle.com,
 kernel-team@...roid.com, devicetree@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 10/11] arm64: dts: exynos: gs101: add the chipid node



On 11/4/25 9:14 AM, Krzysztof Kozlowski wrote:
> On 03/11/2025 11:50, Tudor Ambarus wrote:
>>
>>
>> On 11/3/25 12:18 PM, Krzysztof Kozlowski wrote:
>>> On Fri, Oct 31, 2025 at 12:56:09PM +0000, Tudor Ambarus wrote:
>>>> Add the chipid node.
>>>>
>>>> Signed-off-by: Tudor Ambarus <tudor.ambarus@...aro.org>
>>>> ---
>>>>  arch/arm64/boot/dts/exynos/google/gs101.dtsi | 6 ++++++
>>>>  1 file changed, 6 insertions(+)
>>>>
>>>> diff --git a/arch/arm64/boot/dts/exynos/google/gs101.dtsi b/arch/arm64/boot/dts/exynos/google/gs101.dtsi
>>>> index d06d1d05f36408137a8acd98e43d48ea7d4f4292..11622da2d46ff257b447a3dfdc98abdf29a45b9a 100644
>>>> --- a/arch/arm64/boot/dts/exynos/google/gs101.dtsi
>>>> +++ b/arch/arm64/boot/dts/exynos/google/gs101.dtsi
>>>> @@ -467,6 +467,12 @@ opp-2802000000 {
>>>>  		};
>>>>  	};
>>>>  
>>>> +	chipid {
>>>> +		compatible = "google,gs101-chipid";
>>>
>>> That's not a real device, sorry.
>>>
>>> I had some doubts when reading the bindings, then more when reading
>>> driver - like chipid probe() was basically empty, no single device
>>> access, except calling other kernel subsystem - and now here no single
>>> actual hardware resource, except reference to other node.
>>>
>>> Are you REALLY REALLY sure you have in your datasheet such device as
>>> chipid?
>>>
>>> It is damn basic question, which you should start with.
>>
>> Documentation says that  GS101 "includes a CHIPID block for the software
>> that sends and receives APB interface signals to and from the bus system.
>> The first address of the SFR region (0x1000_0000) contains the product ID."
> 
> So chipid@...0_0000
> 
>>
>> 0x1000_0000 is the base address of the OTP controller (OTP_CON_TOP).
> 
> 
> and efuse@...0_0000 from your other patchset and your sentence above.
> 
> Please add them to DTS and check for warnings.

One would get an unique_unit_address warning, yes.

> 
>>
>> "CHIPID block" tells it's a device, no? But now I think it was just an
>> unfortunate datasheet description. Do you have an advice on how I shall
>> treat this next please? Maybe register to the soc interface directly from
>> the OTP controller driver?
> I think in the SoC it is impossible or at least never happening that you
> create two devices for the same address, therefore either chipid is a
> device or efuse is a device.
> 
Right. The ChipID "block" does not have its own registers. It references
the OTP registers. I'll describe just the efuse device in the DT and
register to the soc interface directly from the efuse driver. Please let
me know if you think there's a better way to handle this.

Thanks,
ta