From: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
To: "Li, Meng" <Meng.Li@windriver.com>
Cc: "Jonathan Cameron" <jic23@kernel.org>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"lars@metafoo.de" <lars@metafoo.de>,
"Michael.Hennerich@analog.com" <Michael.Hennerich@analog.com>,
"pmeerw@pmeerw.net" <pmeerw@pmeerw.net>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>
Subject: Re: [PATCH] driver: adc: ltc2497: return directly after reading the adc conversion value
Date: Tue, 25 May 2021 09:19:02 +0100 [thread overview]
Message-ID: <20210525091902.000074b5@Huawei.com> (raw)
In-Reply-To: <PH0PR11MB519159873BE8CB7ACA227826F1269@PH0PR11MB5191.namprd11.prod.outlook.com>
On Mon, 24 May 2021 02:49:01 +0000
"Li, Meng" <Meng.Li@windriver.com> wrote:
> > -----Original Message-----
> > From: Jonathan Cameron <jic23@kernel.org>
> > Sent: Saturday, May 22, 2021 1:02 AM
> > To: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> > Cc: Li, Meng <Meng.Li@windriver.com>; lars@metafoo.de;
> > Michael.Hennerich@analog.com; pmeerw@pmeerw.net; linux-
> > kernel@vger.kernel.org; linux-iio@vger.kernel.org
> > Subject: Re: [PATCH] driver: adc: ltc2497: return directly after reading the adc
> > conversion value
> >
> > [Please note: This e-mail is from an EXTERNAL e-mail address]
> >
> > On Wed, 19 May 2021 11:21:04 +0200
> > Uwe Kleine-König <u.kleine-koenig@pengutronix.de> wrote:
> >
> > > On Wed, May 12, 2021 at 12:57:25PM +0800, Meng.Li@windriver.com
> > wrote:
> > > > From: Meng Li <Meng.Li@windriver.com>
> > > >
> > > > When read adc conversion value with below command:
> > > > cat /sys/.../iio:device0/in_voltage0-voltage1_raw
> > > > There is an error reported as below:
> > > > ltc2497 0-0014: i2c transfer failed: -EREMOTEIO This i2c transfer
> > > > issue is introduced by commit 69548b7c2c4f ("iio:
> > > > adc: ltc2497: split protocol independent part in a separate module").
> > > > When extract the common code into ltc2497-core.c, it change the code
> > > > logic of function ltc2497core_read(). With wrong reading sequence,
> > > > the action of enable adc channel is sent to chip again during adc
> > > > channel is in conversion status. In this way, there is no ack from
> > > > chip, and then cause i2c transfer failed.
> > > > In order to keep the code logic is the same with original ideal, it
> > > > is need to return direct after reading the adc conversion value.
> > > >
> > > > Fixes: 69548b7c2c4f ("iio: adc: ltc2497: split protocol independent
> > > > part in a separate module ")
> > > > Cc: stable@vger.kernel.org
> > > > Signed-off-by: Meng Li <Meng.Li@windriver.com>
> > > > ---
> > > > drivers/iio/adc/ltc2497.c | 2 ++
> > > > 1 file changed, 2 insertions(+)
> > > >
> > > > diff --git a/drivers/iio/adc/ltc2497.c b/drivers/iio/adc/ltc2497.c
> > > > index 1adddf5a88a9..fd5a66860a47 100644
> > > > --- a/drivers/iio/adc/ltc2497.c
> > > > +++ b/drivers/iio/adc/ltc2497.c
> > > > @@ -41,6 +41,8 @@ static int ltc2497_result_and_measure(struct
> > ltc2497core_driverdata *ddata,
> > > > }
> > > >
> > > > *val = (be32_to_cpu(st->buf) >> 14) - (1 << 17);
> > > > +
> > > > + return ret;
> > >
> > > This looks wrong for me. The idea of the function
> > > ltc2497_result_and_measure is that it reads the result and starts a
> > > new measurement. I guess the problem is that
> > > ltc2497_result_and_measure is called to early, not that it does too much.
> > >
> > > But note I don't have such a system handy to actually debug this any
> > > more.
> >
> > @Meng Li,
> >
> > I see from the datasheet that the device can be used with an external
> > oscillator.
> > Is that the case on your boards, because if so the timing delay of 150msecs
> > may be far too short. If not, perhaps the part is right at the upper end of
> > timings and we just need to add 20% to the 150msecs to be sure of not
> > hitting the limit?
> >
>
> Hi Jonathan,
>
> Thanks for your very professional comments.
> I check my board schematics, the pin 35 f0 is connected to GND, so I use the internal oscillator.
Bad guess :(
> In additional, I am not very understand your comment about the case of using internal oscillator.
> Do you mean that you agree my patch and only need to change 150 into 180?
> #define LTC2497_CONVERSION_TIME_MS 150ULL
> =>
> #define LTC2497_CONVERSION_TIME_MS 180ULL
Yes. Just give a little more time in case the oscillator is running
a little slow.
Jonathan
>
> Thanks,
> Limeng
>
> > Thanks,
> >
> > Jonathan
> >
> >
> > >
> > > Best regards
> > > Uwe
> > >
>
next prev parent reply other threads:[~2021-05-25 8:21 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-12 4:57 [PATCH] driver: adc: ltc2497: return directly after reading the adc conversion value Meng.Li
2021-05-18 17:46 ` Jonathan Cameron
2021-05-19 9:21 ` Uwe Kleine-König
2021-05-21 17:01 ` Jonathan Cameron
2021-05-24 2:49 ` Li, Meng
2021-05-25 8:19 ` Jonathan Cameron [this message]
2021-05-24 2:53 ` Li, Meng
2021-05-25 8:22 ` Felix Knopf
2021-05-25 10:36 ` Li, Meng
2021-06-01 9:28 Meng.Li
2021-06-03 16:20 ` Jonathan Cameron
2021-06-04 2:16 ` Li, Meng
2021-06-04 6:13 ` Uwe Kleine-König
2021-06-04 6:43 ` Li, Meng
2021-06-04 8:20 ` Jonathan Cameron
2021-06-04 8:53 ` Uwe Kleine-König
2021-06-04 9:04 ` Li, Meng
2021-06-04 9:32 ` Uwe Kleine-König
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