linux-kernel - Re: [PATCH v2] i2c: npcm7xx: bug fix timeout (usec instead of msec)

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Date:   Mon, 31 Aug 2020 10:57:31 +0300
From:   Avi Fishman <avifishman70@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Tali Perry <tali.perry1@...il.com>, kunyi@...gle.com,
        xqiu@...gle.com, Benjamin Fair <benjaminfair@...gle.com>,
        Joel Stanley <joel@....id.au>,
        Tomer Maimon <tmaimon77@...il.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] i2c: npcm7xx: bug fix timeout (usec instead of msec)

On Sun, Aug 30, 2020 at 9:01 PM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
>
> On Sun, Aug 30, 2020 at 3:23 PM Tali Perry <tali.perry1@...il.com> wrote:
>
> >
> > i2c: npcm7xx: bug fix timeout (usec instead of msec)
>
> This commit message is awful. Please read [1] as a tutorial how to
> write a commit messages.
>

Would this be better:
i2c: npcm7xx: Fix microsecond timeout calculation

Inside npcm_i2c_master_xfer() we calculate a timeout for the entire
transaction in microseconds, the calculation was wrong so big i2c
massages would timeout before they ended.
This commit fix that.

> [1]: https://chris.beams.io/posts/git-commit/
>
> ...
>
> > -       /* Adaptive TimeOut: astimated time in usec + 100% margin */
> > -       timeout_usec = (2 * 10000 / bus->bus_freq) * (2 + nread + nwrite);
> > +       /*
> > +        * Adaptive TimeOut: estimated time in usec + 100% margin:
> > +        * 2: double the timeout for clock stretching case
> > +        * 9: bits per transaction (including the ack/nack)
>
> > +        * 1000000: micro second in a second
>
> No need. See below.
>
> > +        */
>
> > +       timeout_usec = (2 * 9 * 1000000 / bus->bus_freq) * (2 + nread + nwrite);
>
> USEC_PER_SEC

OK

>
> >         timeout = max(msecs_to_jiffies(35), usecs_to_jiffies(timeout_usec));
> >         if (nwrite >= 32 * 1024 || nread >= 32 * 1024) {
> >                 dev_err(bus->dev, "i2c%d buffer too big\n", bus->num);
>
> --
> With Best Regards,
> Andy Shevchenko



-- 
Regards,
Avi