linux-kernel - Re: [PATCH v1 1/2] dt-bindings: i2c: exynos5: Add samsung,exynos8895-hsi2c compatible

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Message-ID: <3fb8ba3f-3016-4823-bf48-130f173c8f66@kernel.org>
Date: Wed, 18 Dec 2024 10:22:21 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Ivaylo Ivanov <ivo.ivanov.ivanov1@...il.com>,
 Andi Shyti <andi.shyti@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Alim Akhtar <alim.akhtar@...sung.com>
Cc: linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/2] dt-bindings: i2c: exynos5: Add
 samsung,exynos8895-hsi2c compatible

On 17/12/2024 11:04, Ivaylo Ivanov wrote:
> On 12/17/24 11:43, Krzysztof Kozlowski wrote:
>> On 17/12/2024 10:31, Ivaylo Ivanov wrote:
>>> On 12/17/24 11:26, Krzysztof Kozlowski wrote:
>>>> On 17/12/2024 10:08, Ivaylo Ivanov wrote:
>>>>>>>>>        - items:
>>>>>>>>>            - enum:
>>>>>>>>> @@ -94,9 +95,28 @@ allOf:
>>>>>>>>>          - clock-names
>>>>>>>>>  
>>>>>>>>>      else:
>>>>>>>>> -      properties:
>>>>>>>>> -        clocks:
>>>>>>>>> -          maxItems: 1
>>>>>>>>> +      if:
>>>>>>>>> +        properties:
>>>>>>>>> +          compatible:
>>>>>>>>> +            contains:
>>>>>>>>> +              enum:
>>>>>>>>> +                - samsung,exynos8895-hsi2c
>>>>>>>>> +
>>>>>>>>> +      then:
>>>>>>>>> +        properties:
>>>>>>>>> +          clocks:
>>>>>>>> Missing minItems
>>>>>>>>
>>>>>>>>> +            maxItems: 2
>>>>>>>>> +
>>>>>>>>> +          clock-names:
>>>>>>>> Ditto
>>>>>>>>
>>>>>>>>> +            maxItems: 2
>>>>>>>>> +
>>>>>>>>> +        required:
>>>>>>>>> +          - clock-names
>>>>>>>> I don't understand why do you need second, same branch in if, basically
>>>>>>> Because, as I stated in the commit message, we have HSI2C controllers
>>>>>>> both implemented in USIv1 blocks and outside. These that are a part of
>>>>>> On Exynos8895? Where? With the same compatible?
>>>>> hsi2c_0 which has a clock from BUSC and hsi2c_1 to hsi2c_4 which use clocks
>>>>> from PERIC1 (CLK_GOUT_PERIC1_HSI2C_CAM{0,1,2,3}_IPCLK). Why would
>>>>> they need a different compatible though? It's functionally the same i2c design
>>>>> as the one implemented in USIv1 blocks.
>>>> If one block is part of USI and other not, they might not be the same
>>>> I2C blocks, even if interface is similar. If they were the same or even
>>>> functionally the same, they would have the same clock inputs. However
>>> I see, so in such case I should make samsung,exynos8895-hsi2c-nonusi or
>>> something like that?
>>>
>>>> user manual also suggests that there is only one clock, not two (for
>>>> both cases), so they could be functionally equivalent but then number of
>>>> clocks looks incorrect.
>>> That'd be weird. Both according to downstream and upstream clk driver,
>>> for the USI-implemented i2cs we have a pclk and an sclk_usi.
>> Something is not precise here, as usually with Samsung clock topology.
>>
>> First, the non-USI instances have the IPCLK as well, e.g. things like
>> PERIC1_UID_HSI2C_CAM1_IPCLKPORT_iPCLK
>>
>> USI have BLK_PERIC0_UID_USI03_IPCLKPORT_i_SCLK_USI, but that's USI
>> clock, not HSI2C in USI. Datasheet mentions this is UART and SPI special
>> clock, but not I2C.
> 
> That's weird. Don't we need the clock enabled in order for the
> USIv1's HSI2C to work?
The clock goes to USI, so it is enabled, no?

Best regards,
Krzysztof