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

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Message-ID: <CAJX_Q+1tz7BYL+CvXnc=zAamPiZDEFAASv9a7YoWGmzqYL+cUg@mail.gmail.com>
Date:   Mon, 28 Mar 2022 18:31:24 -0400
From:   Lucas Tanure <tanure@...ux.com>
To:     Kevin Hilman <khilman@...libre.com>
Cc:     Neil Armstrong <narmstrong@...libre.com>,
        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

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.

Is that enough?

Thanks
Lucas