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

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Message-ID: <bfc2c9f9-a8cb-84a8-0800-fc90f6ec2eda@amd.com>
Date:   Wed, 3 May 2023 10:02:13 +0200
From:   Michal Simek <michal.simek@....com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        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 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?

Thanks,
Michal