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

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Message-ID: <56c5788a-2d49-4abb-af4b-65a11bdc4094@kernel.org>
Date: Tue, 17 Dec 2024 10:43:05 +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 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. The PCLK is used for HSI2C iPCLK.


Best regards,
Krzysztof