linux-kernel - Re: [PATCH 0/3] Ensure Low period of SCL is correct

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Date:   Mon, 4 Apr 2022 21:00:20 +0300
From:   Vyacheslav <adeep@...ina.in>
To:     Neil Armstrong <narmstrong@...libre.com>, tanure@...ux.com,
        Kevin Hilman <khilman@...libre.com>
Cc:     Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        linux-i2c@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] Ensure Low period of SCL is correct



04.04.2022 11:01, Neil Armstrong wrote:
> Hi,
> 
> On 29/03/2022 00:31, Lucas Tanure wrote:
>> On Mon, 28 Mar 2022, 21:37 Kevin Hilman, <khilman@...libre.com> wrote:
>>>
>>> Hi Lucas,
>>>
>>> Lucas Tanure <tanure@...ux.com> writes:
>>>
>>>> The default duty cycle of 33% is less than the required
>>>> by the I2C specs for the LOW period of the SCL clock.
>>>>
>>>> So, for 100Khz or less, use 50%H/50%L duty cycle, and
>>>> for the clock above 100Khz, use 40%H/60%L duty cycle.
>>>> That ensures the low period of SCL is always more than
>>>> the minimum required by the specs at any given frequency.
>>>
>>> Thanks for the fixes!
>>>
>>> This is going to affect all SoCs, so ould you please summarize how your
>>> changes were tested, and on which SoCs & boards?
>>>
>>> Thanks,
>>>
>>> Kevin
>>
>> Hi,
>>
>> I only tested against the vim3 board, measured the bus with a Saleae
>> logic pro 16.
>> The measurements were with 100k, 400k, and a few in-between frequencies.
> 
> Thanks, it's a great addition to have !
> 
>>
>> Is that enough?
> 
> A test on GXL/GXM (VIM1 or VIM2) & GXBB (Odroid-C2) devices is lacking 
> before we
> can merge this.
> 
> If I find some time, I'll have a try, but everyone is welcome testing 
> this serie
> and report if it still works fine for them.
> 
> Vyacheslav, do you think you can test on your JetHub devices ? it would 
> validate GXL & AXG.

It builds ok on 5.17. JetHub H1/D1 has only rtc clock (pcf8563) and 
1-wire controller (ds2482) on i2c bus. I did't see any difference with 
or without patches. all works at first look.

Vyacheslav