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

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Message-ID: <685eb8ab-2767-43da-80d0-ec77ff779d86@gmail.com>
Date: Tue, 17 Dec 2024 19:42:32 +0200
From: Markuss Broks <markuss.broks@...il.com>
To: Krzysztof Kozlowski <krzk@...nel.org>,
 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

Hi Krzysztof,

On 12/17/24 11:43 AM, 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. The PCLK is used for HSI2C iPCLK.

In USI, USI PCLK is used for the internal AMBA APB bus clock and the 
IPCLK signal is used for the peripheral controller blocks (i2c/spi/uart).

So perhaps we have it described incorrectly, and the hsi2c controllers 
(at least on E8895) should take only one clock input (IPCLK), and USI 
block should take the PCLK input.


>
>
> Best regards,
> Krzysztof
>

- Markuss