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Date: Sun, 8 Oct 2017 11:07:56 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Stefan Brüns <stefan.bruens@...h-aachen.de>
Cc: <linux-iio@...r.kernel.org>,
Peter Meerwald-Stadler <pmeerw@...erw.net>,
<linux-kernel@...r.kernel.org>, "Andrew F . Davis" <afd@...com>,
"Javier Martinez Canillas" <javier@....samsung.com>,
Lars-Peter Clausen <lars@...afoo.de>,
Hartmut Knaack <knaack.h@....de>,
Maciej Purski <m.purski@...sung.com>
Subject: Re: [PATCH 3/3] iio: adc: ina2xx: Allow setting Shunt Voltage PGA
gain and Bus Voltage range
On Sun, 1 Oct 2017 21:48:18 +0200
Stefan Brüns <stefan.bruens@...h-aachen.de> wrote:
> Reducing shunt and bus voltage range improves the accuracy, so allow
> altering the default settings.
>
> Both settings are exposed as gain values. While for the shunt voltage
> this is straightforward, the bus range settings of 32V (default) and 16V
> are mapped to gain values of 1 resp. 2, to provide a uniform API to
> userspace.
>
> As the gain settings are incorporated into the raw values by the sensor
> itself, adjusting of the scale attributes is not necessary.
>
> Signed-off-by: Stefan Brüns <stefan.bruens@...h-aachen.de>
cc'd Maciej Purski who is working to improve the current calibration
elements - I'd like you both to review each others patches if possible
as the ABI is getting complex in here!
I think what you have here won't interfere with Maciej's work, but
would like you two to confirm that. Note that patch set probably
needs a revision as I've suggested a rather different approach.
Thanks,
Jonathan
>
> ---
>
> drivers/iio/adc/ina2xx-adc.c | 111 +++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 108 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iio/adc/ina2xx-adc.c b/drivers/iio/adc/ina2xx-adc.c
> index 1930f853e8c5..7e9ce43ad15d 100644
> --- a/drivers/iio/adc/ina2xx-adc.c
> +++ b/drivers/iio/adc/ina2xx-adc.c
> @@ -48,8 +48,10 @@
> #define INA2XX_MAX_REGISTERS 8
>
> /* settings - depend on use case */
> -#define INA219_CONFIG_DEFAULT 0x399F /* PGA=8 */
> +#define INA219_CONFIG_DEFAULT 0x399F /* PGA=1/8, BRNG=32V */
> #define INA219_DEFAULT_IT 532
> +#define INA219_DEFAULT_BRNG 1 /* 32V */
> +#define INA219_DEFAULT_PGA 125 /* 1000/8 */
> #define INA226_CONFIG_DEFAULT 0x4327
> #define INA226_DEFAULT_AVG 4
> #define INA226_DEFAULT_IT 1110
> @@ -62,6 +64,14 @@
> */
> #define INA2XX_MODE_MASK GENMASK(3, 0)
>
> +/* Gain for VShunt: 1/8 (default), 1/4, 1/2, 1 */
> +#define INA219_PGA_MASK GENMASK(12, 11)
> +#define INA219_SHIFT_PGA(val) ((val) << 11)
> +
> +/* VBus range: 32V (default), 16V */
> +#define INA219_BRNG_MASK BIT(13)
> +#define INA219_SHIFT_BRNG(val) ((val) << 13)
> +
> /* Averaging for VBus/VShunt/Power */
> #define INA226_AVG_MASK GENMASK(11, 9)
> #define INA226_SHIFT_AVG(val) ((val) << 9)
> @@ -131,6 +141,8 @@ struct ina2xx_chip_info {
> int avg;
> int int_time_vbus; /* Bus voltage integration time uS */
> int int_time_vshunt; /* Shunt voltage integration time uS */
> + int range_vbus; /* Bus voltage maximum in V */
> + int pga_gain_vshunt; /* Shunt voltage PGA gain */
> bool allow_async_readout;
> };
>
> @@ -227,6 +239,18 @@ static int ina2xx_read_raw(struct iio_dev *indio_dev,
> *val = 1;
> return IIO_VAL_INT;
> }
> +
> + case IIO_CHAN_INFO_HARDWAREGAIN:
> + switch (chan->address) {
> + case INA2XX_SHUNT_VOLTAGE:
> + *val = chip->pga_gain_vshunt;
> + *val2 = 1000;
> + return IIO_VAL_FRACTIONAL;
> +
> + case INA2XX_BUS_VOLTAGE:
> + *val = chip->range_vbus == 32 ? 1 : 2;
> + return IIO_VAL_INT;
> + }
> }
>
> return -EINVAL;
> @@ -361,6 +385,74 @@ static int ina219_set_int_time_vshunt(struct ina2xx_chip_info *chip,
> return 0;
> }
>
> +static const int ina219_vbus_range_tab[] = { 1, 2 };
> +static int ina219_set_vbus_range_denom(struct ina2xx_chip_info *chip,
> + unsigned int range,
> + unsigned int *config)
> +{
> + if (range == 1)
> + chip->range_vbus = 32;
> + else if (range == 2)
> + chip->range_vbus = 16;
> + else
> + return -EINVAL;
> +
> + *config &= ~INA219_BRNG_MASK;
> + *config |= INA219_SHIFT_BRNG(range == 1 ? 1 : 0) & INA219_BRNG_MASK;
> +
> + return 0;
> +}
> +
> +static const int ina219_vshunt_gain_tab[] = { 125, 250, 500, 1000 };
> +static const int ina219_vshunt_gain_frac[] = {
> + 125, 1000, 250, 1000, 500, 1000, 1000, 1000 };
> +
> +static int ina219_set_vshunt_pga_gain(struct ina2xx_chip_info *chip,
> + unsigned int gain,
> + unsigned int *config)
> +{
> + int bits;
> +
> + if (gain < 125 || gain > 1000)
> + return -EINVAL;
> +
> + bits = find_closest(gain, ina219_vshunt_gain_tab,
> + ARRAY_SIZE(ina219_vshunt_gain_tab));
> +
> + chip->pga_gain_vshunt = ina219_vshunt_gain_tab[bits];
> + bits = 3 - bits;
> +
> + *config &= ~INA219_PGA_MASK;
> + *config |= INA219_SHIFT_PGA(bits) & INA219_PGA_MASK;
> +
> + return 0;
> +}
> +
> +static int ina2xx_read_avail(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + const int **vals, int *type, int *length,
> + long mask)
> +{
> + switch (mask) {
> + case IIO_CHAN_INFO_HARDWAREGAIN:
> + switch (chan->address) {
> + case INA2XX_SHUNT_VOLTAGE:
> + *type = IIO_VAL_FRACTIONAL;
> + *length = sizeof(ina219_vshunt_gain_frac) / sizeof(int);
> + *vals = ina219_vshunt_gain_frac;
> + return IIO_AVAIL_LIST;
> +
> + case INA2XX_BUS_VOLTAGE:
> + *type = IIO_VAL_INT;
> + *length = sizeof(ina219_vbus_range_tab) / sizeof(int);
> + *vals = ina219_vbus_range_tab;
> + return IIO_AVAIL_LIST;
> + }
> + }
> +
> + return -EINVAL;
> +}
> +
> static int ina2xx_write_raw(struct iio_dev *indio_dev,
> struct iio_chan_spec const *chan,
> int val, int val2, long mask)
> @@ -403,6 +495,14 @@ static int ina2xx_write_raw(struct iio_dev *indio_dev,
> }
> break;
>
> + case IIO_CHAN_INFO_HARDWAREGAIN:
> + if (chan->address == INA2XX_SHUNT_VOLTAGE)
> + ret = ina219_set_vshunt_pga_gain(chip, val * 1000000 +
> + val2, &tmp);
> + else
> + ret = ina219_set_vbus_range_denom(chip, val, &tmp);
> + break;
> +
> default:
> ret = -EINVAL;
> }
> @@ -547,7 +647,10 @@ static ssize_t ina2xx_shunt_resistor_store(struct device *dev,
> .channel = (_index), \
> .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
> BIT(IIO_CHAN_INFO_SCALE) | \
> - BIT(IIO_CHAN_INFO_INT_TIME), \
> + BIT(IIO_CHAN_INFO_INT_TIME) | \
> + BIT(IIO_CHAN_INFO_HARDWAREGAIN), \
> + .info_mask_separate_available = \
> + BIT(IIO_CHAN_INFO_HARDWAREGAIN), \
> .info_mask_shared_by_dir = BIT(IIO_CHAN_INFO_SAMP_FREQ), \
> .scan_index = (_index), \
> .scan_type = { \
> @@ -758,7 +861,6 @@ static IIO_CONST_ATTR_NAMED(ina226_integration_time_available,
> integration_time_available,
> "0.000140 0.000204 0.000332 0.000588 0.001100 0.002116 0.004156 0.008244");
>
> -
> static IIO_DEVICE_ATTR(in_allow_async_readout, S_IRUGO | S_IWUSR,
> ina2xx_allow_async_readout_show,
> ina2xx_allow_async_readout_store, 0);
> @@ -793,6 +895,7 @@ static const struct iio_info ina219_info = {
> .driver_module = THIS_MODULE,
> .attrs = &ina219_attribute_group,
> .read_raw = ina2xx_read_raw,
> + .read_avail = ina2xx_read_avail,
> .write_raw = ina2xx_write_raw,
> .debugfs_reg_access = ina2xx_debug_reg,
> };
> @@ -874,6 +977,8 @@ static int ina2xx_probe(struct i2c_client *client,
> chip->avg = 1;
> ina219_set_int_time_vbus(chip, INA219_DEFAULT_IT, &val);
> ina219_set_int_time_vshunt(chip, INA219_DEFAULT_IT, &val);
> + ina219_set_vbus_range_denom(chip, INA219_DEFAULT_BRNG, &val);
> + ina219_set_vshunt_pga_gain(chip, INA219_DEFAULT_PGA, &val);
> }
>
> ret = ina2xx_init(chip, val);
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