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Message-ID: <652e2497-d091-9468-a4ee-983bcc626d6b@kernel.org>
Date: Mon, 1 May 2017 01:22:52 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Eva Rachel Retuya <eraretuya@...il.com>, linux-iio@...r.kernel.org
Cc: knaack.h@....de, lars@...afoo.de, pmeerw@...erw.net,
dmitry.torokhov@...il.com, michael.hennerich@...log.com,
daniel.baluta@...il.com, amsfield22@...il.com,
florian.vaussard@...g-vd.ch, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] iio: accel: adxl345_core: Introduce set_mode and
data_ready functions
On 29/04/17 08:48, Eva Rachel Retuya wrote:
> Move code that enables measurement/standby mode into its own function
> and call that function when appropriate. Previously, we set the sensor
> to measurement in probe and back to standby during remove. Change it
> here to only enter measurement mode when request for data is initiated.
>
> The DATA_READY bit is always set if the corresponding event occurs.
> Introduce the data_ready function that monitors the INT_SOURCE register
> of this bit. This is done to ensure consistent readings.
>
> Signed-off-by: Eva Rachel Retuya <eraretuya@...il.com>
> ---
> Changes in v2:
> * Make function naming more clear: drdy -> data_ready
> * Switch from while to do..while
> * Rename regval to val
> * Switch to usleep_range() for shorter delay
> * Add comment to justify delay
> * Change error code -EIO to -EAGAIN
> * Endianness issue: scrap the get_triple function entirely, make no
> changes in terms of reading registers in read_raw
> * Introduce mutex here rather than in succeeding patch
> * Probe:
> * Fix random whitespace omission
> * Remove configuring to standby mode, the device powers on in standby
> mode so this is not needed
>
> drivers/iio/accel/adxl345_core.c | 84 +++++++++++++++++++++++++++++++++-------
> 1 file changed, 69 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/iio/accel/adxl345_core.c b/drivers/iio/accel/adxl345_core.c
> index 9ccb582..b8a212c 100644
> --- a/drivers/iio/accel/adxl345_core.c
> +++ b/drivers/iio/accel/adxl345_core.c
> @@ -8,6 +8,7 @@
> * directory of this archive for more details.
> */
>
> +#include <linux/delay.h>
> #include <linux/module.h>
> #include <linux/regmap.h>
>
> @@ -17,6 +18,7 @@
>
> #define ADXL345_REG_DEVID 0x00
> #define ADXL345_REG_POWER_CTL 0x2D
> +#define ADXL345_REG_INT_SOURCE 0x30
> #define ADXL345_REG_DATA_FORMAT 0x31
> #define ADXL345_REG_DATAX0 0x32
> #define ADXL345_REG_DATAY0 0x34
> @@ -25,6 +27,10 @@
> #define ADXL345_POWER_CTL_MEASURE BIT(3)
> #define ADXL345_POWER_CTL_STANDBY 0x00
>
> +/* INT_ENABLE/INT_MAP/INT_SOURCE bits */
> +#define ADXL345_INT_DATA_READY BIT(7)
> +#define ADXL345_INT_OVERRUN 0
> +
> #define ADXL345_DATA_FORMAT_FULL_RES BIT(3) /* Up to 13-bits resolution */
> #define ADXL345_DATA_FORMAT_2G 0
> #define ADXL345_DATA_FORMAT_4G 1
> @@ -44,9 +50,49 @@ static const int adxl345_uscale = 38300;
>
> struct adxl345_data {
> struct regmap *regmap;
> + struct mutex lock; /* protect this data structure */
> u8 data_range;
> };
>
> +static int adxl345_set_mode(struct adxl345_data *data, u8 mode)
> +{
> + struct device *dev = regmap_get_device(data->regmap);
> + int ret;
> +
> + ret = regmap_write(data->regmap, ADXL345_REG_POWER_CTL, mode);
> + if (ret < 0) {
> + dev_err(dev, "Failed to set power mode, %d\n", ret);
> + return ret;
drop the return ret here and just return ret at the end of the function.
One of the static checkers will probably moan about this otherwise.
> + }
> +
> + return 0;
> +}
> +
> +static int adxl345_data_ready(struct adxl345_data *data)
> +{
So this is a polling the dataready bit. Will ensure we always
get fresh data when a read occurs. Please add a comment to
that effect as that's not always how devices work.
> + struct device *dev = regmap_get_device(data->regmap);
> + int tries = 5;
> + u32 val;
> + int ret;
> +
> + do {
> + /*
> + * 1/ODR + 1.1ms; 11.1ms at ODR of 0.10 Hz
> + * Sensor currently operates at default ODR of 100 Hz
> + */
> + usleep_range(1100, 11100);
That's a huge range to allow... I'm not following the argument for why.
Or do we have a stray 0?
> +
> + ret = regmap_read(data->regmap, ADXL345_REG_INT_SOURCE, &val);
> + if (ret < 0)
> + return ret;
> + if ((val & ADXL345_INT_DATA_READY) == ADXL345_INT_DATA_READY)
> + return 0;
> + } while (--tries);
> + dev_err(dev, "Data is not yet ready, try again.\n");
> +
This is almost certainly a hardware fault. I'd be more brutal with
the error and return -EIO. If you get here your hardware is very unlikely
to be working correctly if you try again.
> + return -EAGAIN;
> +}
> +
> #define ADXL345_CHANNEL(reg, axis) { \
> .type = IIO_ACCEL, \
> .modified = 1, \
> @@ -72,6 +118,19 @@ static int adxl345_read_raw(struct iio_dev *indio_dev,
>
> switch (mask) {
> case IIO_CHAN_INFO_RAW:
> + mutex_lock(&data->lock);
> + ret = adxl345_set_mode(data, ADXL345_POWER_CTL_MEASURE);
> + if (ret < 0) {
> + mutex_unlock(&data->lock);
> + return ret;
> + }
> +
> + ret = adxl345_data_ready(data);
> + if (ret < 0) {
> + adxl345_set_mode(data, ADXL345_POWER_CTL_STANDBY);
> + mutex_unlock(&data->lock);
What is the logic that puts the mutex_unlock here in the error case
and before the set_mode in the normal path? Even if it doesn't
matter make them the same as it is less likely to raise questions
in the future!
> + return ret;
> + }
> /*
> * Data is stored in adjacent registers:
> * ADXL345_REG_DATA(X0/Y0/Z0) contain the least significant byte
> @@ -79,10 +138,15 @@ static int adxl345_read_raw(struct iio_dev *indio_dev,
> */
> ret = regmap_bulk_read(data->regmap, chan->address, ®val,
> sizeof(regval));
> - if (ret < 0)
> + mutex_unlock(&data->lock);
> + if (ret < 0) {
> + adxl345_set_mode(data, ADXL345_POWER_CTL_STANDBY);
> return ret;
> + }
>
> *val = sign_extend32(le16_to_cpu(regval), 12);
> + adxl345_set_mode(data, ADXL345_POWER_CTL_STANDBY);
> +
> return IIO_VAL_INT;
> case IIO_CHAN_INFO_SCALE:
> *val = 0;
> @@ -136,6 +200,8 @@ int adxl345_core_probe(struct device *dev, struct regmap *regmap,
> return ret;
> }
>
> + mutex_init(&data->lock);
> +
> indio_dev->dev.parent = dev;
> indio_dev->name = name;
> indio_dev->info = &adxl345_info;
> @@ -143,20 +209,9 @@ int adxl345_core_probe(struct device *dev, struct regmap *regmap,
> indio_dev->channels = adxl345_channels;
> indio_dev->num_channels = ARRAY_SIZE(adxl345_channels);
>
> - /* Enable measurement mode */
> - ret = regmap_write(data->regmap, ADXL345_REG_POWER_CTL,
> - ADXL345_POWER_CTL_MEASURE);
> - if (ret < 0) {
> - dev_err(dev, "Failed to enable measurement mode: %d\n", ret);
> - return ret;
> - }
> -
> ret = iio_device_register(indio_dev);
> - if (ret < 0) {
> + if (ret < 0)
> dev_err(dev, "iio_device_register failed: %d\n", ret);
> - regmap_write(data->regmap, ADXL345_REG_POWER_CTL,
> - ADXL345_POWER_CTL_STANDBY);
> - }
>
> return ret;
> }
> @@ -169,8 +224,7 @@ int adxl345_core_remove(struct device *dev)
>
> iio_device_unregister(indio_dev);
>
> - return regmap_write(data->regmap, ADXL345_REG_POWER_CTL,
> - ADXL345_POWER_CTL_STANDBY);
> + return adxl345_set_mode(data, ADXL345_POWER_CTL_STANDBY);
Under what circumstances would we not already be in the correct state?
A brief comment here would be good.
> }
> EXPORT_SYMBOL_GPL(adxl345_core_remove);
>
>
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