linux-kernel - Re: [PATCH] ARM: zynq: dts: Setting default i2c clock frequency to 400kHz

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Message-ID: <1d11d36b-9cfa-4d39-c521-aab2153e49a9@linaro.org>
Date:   Wed, 3 May 2023 10:06:12 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Michal Simek <michal.simek@....com>, linux-kernel@...r.kernel.org,
        monstr@...str.eu, michal.simek@...inx.com, git@...inx.com
Cc:     Varalaxmi Bingi <varalaxmi.bingi@....com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: zynq: dts: Setting default i2c clock frequency to
 400kHz

On 03/05/2023 10:02, Michal Simek wrote:
> 
> 
> On 5/3/23 09:40, Krzysztof Kozlowski wrote:
>> On 03/05/2023 09:27, Michal Simek wrote:
>>>
>>>
>>> On 5/2/23 22:13, Krzysztof Kozlowski wrote:
>>>> CAUTION: This message has originated from an External Source. Please use proper judgment and caution when opening attachments, clicking links, or responding to this email.
>>>>
>>>>
>>>> On 02/05/2023 15:53, Michal Simek wrote:
>>>>> From: Varalaxmi Bingi <varalaxmi.bingi@....com>
>>>>>
>>>>> Setting default i2c clock frequency for Zynq to maximum rate of 400kHz.
>>>>> Current default value is 100kHz.
>>>>>
>>>>> Signed-off-by: Varalaxmi Bingi <varalaxmi.bingi@....com>
>>>>> Signed-off-by: Michal Simek <michal.simek@....com>
>>>>> ---
>>>>>
>>>>>    arch/arm/boot/dts/zynq-7000.dtsi | 2 ++
>>>>>    1 file changed, 2 insertions(+)
>>>>>
>>>>> diff --git a/arch/arm/boot/dts/zynq-7000.dtsi b/arch/arm/boot/dts/zynq-7000.dtsi
>>>>> index cd9931f6bcbd..a7db3f3009f2 100644
>>>>> --- a/arch/arm/boot/dts/zynq-7000.dtsi
>>>>> +++ b/arch/arm/boot/dts/zynq-7000.dtsi
>>>>> @@ -149,6 +149,7 @@ i2c0: i2c@...04000 {
>>>>>                         clocks = <&clkc 38>;
>>>>>                         interrupt-parent = <&intc>;
>>>>>                         interrupts = <0 25 4>;
>>>>> +                     clock-frequency = <400000>;
>>>>
>>>> I think this should be rather property of the board, because it depends
>>>> on I2C devices, right?
>>>
>>> We have 15+ boards with i2c connected and from this count I am aware about only
>>> one configuration which is not working on 400k.
>>> It is a question if make sense to update all boards (except for 1 and not all in
>>> kernel yet) to 400k or just say 400k is default and if there is any issue use
>>> lower frequency.
>>> Obviously this patch is setting up 400k as default and let "problematic" boards
>>> to setup lower freq.
>>> The same approach was used for modepin description.
>>>
>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/arm64/boot/dts/xilinx/zynqmp.dtsi?h=v6.3&id=53ba1b2bdaf7f481fdd878e9c18cd0e54081fac9
>>>
>>> The next point is that 100k is default in Linux but doesn't mean it is default
>>> in other projects.
>>>
>>> But if you think that it must be board property I think we should setup 100k as
>>> default in this file too to make it clear.
>>
>> No, if it is conscious choice, it's fine.
> 
> Is it Ack then or you want me to extend commit message?

Ack, although you don't need my acks for your platform :)

FWIW:

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>

Best regards,
Krzysztof