From: Jonathan Cameron <jic23@kernel.org>
To: Meng.Li@windriver.com
Cc: lars@metafoo.de, Michael.Hennerich@analog.com, pmeerw@pmeerw.net,
u.kleine-koenig@pengutronix.de, linux-kernel@vger.kernel.org,
linux-iio@vger.kernel.org
Subject: Re: [PATCH] driver: adc: ltc2497: return directly after reading the adc conversion value
Date: Thu, 3 Jun 2021 17:20:25 +0100 [thread overview]
Message-ID: <20210603172025.314b5ced@jic23-huawei> (raw)
In-Reply-To: <20210601092805.18385-1-Meng.Li@windriver.com>
On Tue, 1 Jun 2021 17:28:05 +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.
>
> v2:
> According to ltc2497 datasheet, the max value of conversion time is
> 149.9 ms. So, add 20% to the 150msecs so that there is enough time
> for data conversion.
Version change logs go below the --- as we don't want to preserve them
forever in the git history.
I may have lost track of the discussion, but I thought the idea was that perhaps
the longer time period would remove the need for the early return?
Thanks,
Jonathan
>
> 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 ++
> drivers/iio/adc/ltc2497.h | 2 +-
> 2 files changed, 3 insertions(+), 1 deletion(-)
>
> 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;
> }
>
> ret = i2c_smbus_write_byte(st->client,
> diff --git a/drivers/iio/adc/ltc2497.h b/drivers/iio/adc/ltc2497.h
> index d0b42dd6b8ad..e451930837d8 100644
> --- a/drivers/iio/adc/ltc2497.h
> +++ b/drivers/iio/adc/ltc2497.h
> @@ -2,7 +2,7 @@
>
> #define LTC2497_ENABLE 0xA0
> #define LTC2497_CONFIG_DEFAULT LTC2497_ENABLE
> -#define LTC2497_CONVERSION_TIME_MS 150ULL
> +#define LTC2497_CONVERSION_TIME_MS 180ULL
>
> struct ltc2497core_driverdata {
> struct regulator *ref;
next prev parent reply other threads:[~2021-06-03 16:18 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-01 9:28 [PATCH] driver: adc: ltc2497: return directly after reading the adc conversion value Meng.Li
2021-06-03 16:20 ` Jonathan Cameron [this message]
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
-- strict thread matches above, loose matches on Subject: below --
2021-05-12 4:57 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
2021-05-24 2:53 ` Li, Meng
2021-05-25 8:22 ` Felix Knopf
2021-05-25 10:36 ` Li, Meng
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