linux-kernel - Re: [PATCH v4 3/6] i2c: npcm: Modify timeout evaluation mechanism

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Message-ID: <CACD3sJZ8zSSO9kE30qAAYFf-qw+LQ3RRUbPgqnWO_BsxFV2fOw@mail.gmail.com>
Date: Fri, 27 Sep 2024 10:03:42 +0800
From: Tyrone Ting <warp5tw@...il.com>
To: Andi Shyti <andi.shyti@...nel.org>
Cc: avifishman70@...il.com, tmaimon77@...il.com, tali.perry1@...il.com, 
	venture@...gle.com, yuenn@...gle.com, benjaminfair@...gle.com, 
	andriy.shevchenko@...ux.intel.com, wsa@...nel.org, rand.sec96@...il.com, 
	wsa+renesas@...g-engineering.com, tali.perry@...oton.com, 
	Avi.Fishman@...oton.com, tomer.maimon@...oton.com, KWLIU@...oton.com, 
	JJLIU0@...oton.com, kfting@...oton.com, openbmc@...ts.ozlabs.org, 
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/6] i2c: npcm: Modify timeout evaluation mechanism

Hi Andi:

Thank you for your feedback.

Your comments will be addressed.

Andi Shyti <andi.shyti@...nel.org> 於 2024年9月26日 週四 上午4:24寫道：
>
> Hi Tyrone,
>
> ...
>
> > diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
> > index 2d034503d8bc..68f3d47323ab 100644
> > --- a/drivers/i2c/busses/i2c-npcm7xx.c
> > +++ b/drivers/i2c/busses/i2c-npcm7xx.c
> > @@ -2132,19 +2132,12 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> >               }
> >       }
> >
> > -     /*
> > -      * Adaptive TimeOut: estimated time in usec + 100% margin:
> > -      * 2: double the timeout for clock stretching case
> > -      * 9: bits per transaction (including the ack/nack)
> > -      */
> > -     timeout_usec = (2 * 9 * USEC_PER_SEC / bus->bus_freq) * (2 + nread + nwrite);
> > -     timeout = max_t(unsigned long, bus->adap.timeout, usecs_to_jiffies(timeout_usec));
> >       if (nwrite >= 32 * 1024 || nread >= 32 * 1024) {
> >               dev_err(bus->dev, "i2c%d buffer too big\n", bus->num);
> >               return -EINVAL;
> >       }
> >
> > -     time_left = jiffies + timeout + 1;
> > +     time_left = jiffies + bus->adap.timeout / bus->adap.retries + 1;
> >       do {
> >               /*
> >                * we must clear slave address immediately when the bus is not
> > @@ -2183,6 +2176,14 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> >       if (npcm_i2c_master_start_xmit(bus, slave_addr, nwrite, nread,
> >                                      write_data, read_data, read_PEC,
> >                                      read_block)) {
> > +             /*
> > +              * Adaptive TimeOut: estimated time in usec + 100% margin:
> > +              * 2: double the timeout for clock stretching case
> > +              * 9: bits per transaction (including the ack/nack)
> > +              */
> > +             timeout_usec = (2 * 9 * USEC_PER_SEC / bus->bus_freq) * (2 + nread + nwrite);
> > +             timeout = max_t(unsigned long, bus->adap.timeout / bus->adap.retries,
> > +                             usecs_to_jiffies(timeout_usec));
> >               time_left = wait_for_completion_timeout(&bus->cmd_complete,
> >                                                       timeout);
> >
> > @@ -2308,7 +2309,7 @@ static int npcm_i2c_probe_bus(struct platform_device *pdev)
> >       adap = &bus->adap;
> >       adap->owner = THIS_MODULE;
> >       adap->retries = 3;
> > -     adap->timeout = msecs_to_jiffies(35);
> > +     adap->timeout = 2 * HZ;
>
> Same here, I need some good description of why timeout is set to
> 2 seconds. If the datasheet says 35ms, I do not exclude that
> someone in the future will send a patch saying "we don't need to
> wait 2 seconds, wait 35ms as per datasheet".
>
> Thanks,
> Andi
>
> >       adap->algo = &npcm_i2c_algo;
> >       adap->quirks = &npcm_i2c_quirks;
> >       adap->algo_data = bus;
> > --
> > 2.34.1
> >

Have a nice day.

Regards,
Tyrone