linux-kernel - Re: [PATCH v3 1/2] iio: ina2xx: add support for TI INA2xx Power Monitors

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Date:	Wed, 16 Dec 2015 18:54:44 +0100
From:	Marc Titinger <mtitinger@...libre.com>
To:	"Andrew F. Davis" <afd@...com>, jic23@...nel.org, knaack.h@....de,
	lars@...afoo.de, pmeerw@...erw.net, linux@...ck-us.net,
	jdelvare@...e.com
Cc:	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
	lm-sensors@...sensors.org
Subject: Re: [PATCH v3 1/2] iio: ina2xx: add support for TI INA2xx Power
 Monitors

On 16/12/2015 18:45, Andrew F. Davis wrote:
> On 12/07/2015 03:09 AM, Marc Titinger wrote:
>> +#define INA2XX_CHAN(_type, _index, _address) { \
>> +    .type = (_type), \
>> +    .address = (_address), \
>> +    .indexed = 1, \
>> +    .channel = (_index), \
>> +    .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
>> +    .info_mask_shared_by_dir = BIT(IIO_CHAN_INFO_SAMP_FREQ) | \
>> +                   BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
>> +    .scan_index = (_index), \
>> +    .scan_type = { \
>> +        .sign = 'u', \
>> +        .realbits = 16, \
>> +        .storagebits = 16, \
>> +        .endianness = IIO_BE, \
>
> ^^^^ See below.
>
>> +    } \
>> +}
>> +
>> +/*
>> + * Sampling Freq is a consequence of the integration times of
>> + * the Voltage channels.
>> + */
>> +#define INA2XX_CHAN_VOLTAGE(_index, _address) { \
>> +    .type = IIO_VOLTAGE, \
>> +    .address = (_address), \
>> +    .indexed = 1, \
>> +    .channel = (_index), \
>> +    .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
>> +                  BIT(IIO_CHAN_INFO_INT_TIME), \
>> +    .scan_index = (_index), \
>> +    .scan_type = { \
>> +        .sign = 'u', \
>> +        .realbits = 16, \
>> +        .storagebits = 16, \
>> +        .endianness = IIO_BE, \
>> +    } \
>> +}
>> +
>> +static const struct iio_chan_spec ina2xx_channels[] = {
>> +    INA2XX_CHAN_VOLTAGE(0, INA2XX_SHUNT_VOLTAGE),
>> +    INA2XX_CHAN_VOLTAGE(1, INA2XX_BUS_VOLTAGE),
>> +    INA2XX_CHAN(IIO_CURRENT, 2, INA2XX_CURRENT),
>> +    INA2XX_CHAN(IIO_POWER, 3, INA2XX_POWER),
>> +    IIO_CHAN_SOFT_TIMESTAMP(4),
>> +};
>> +
>> +static int ina2xx_work_buffer(struct iio_dev *indio_dev)
>> +{
>> +    struct ina2xx_chip_info *chip = iio_priv(indio_dev);
>> +    unsigned short data[8];
>> +    int bit, ret, i = 0;
>> +    unsigned long buffer_us, elapsed_us;
>> +    s64 time_a, time_b;
>> +    unsigned int alert;
>> +
>> +    time_a = iio_get_time_ns();
>> +
>> +    /*
>> +     * Because the timer thread and the chip conversion clock
>> +     * are asynchronous, the period difference will eventually
>> +     * result in reading V[k-1] again, or skip V[k] at time Tk.
>> +     * In order to resync the timer with the conversion process
>> +     * we check the ConVersionReadyFlag.
>> +     * On hardware that supports using the ALERT pin to toggle a
>> +     * GPIO a triggered buffer could be used instead.
>> +     * For now, we pay for that extra read of the ALERT register
>> +     */
>> +    do {
>> +        ret = regmap_read(chip->regmap, INA226_ALERT_MASK,
>> +                  &alert);
>> +        if (ret < 0)
>> +            return ret;
>> +
>> +        alert &= INA266_CVRF;
>> +        trace_printk("Conversion ready: %d\n", !!alert);
>> +
>> +    } while (!alert);
>> +
>> +    /*
>> +     * Single register reads: bulk_read will not work with ina226
>> +     * as there is no auto-increment of the address register for
>> +     * data length longer than 16bits.
>> +     */
>> +    for_each_set_bit(bit, indio_dev->active_scan_mask,
>> +             indio_dev->masklength) {
>> +        unsigned int val;
>> +
>> +        ret = regmap_read(chip->regmap,
>> +                  INA2XX_SHUNT_VOLTAGE + bit, &val);
>> +        if (ret < 0)
>> +            return ret;
>> +
>> +        data[i++] = val;
>
> The read above seems to fill the buffer in CPU order, but above
> IIO_BE is specified, this should probably be IIO_CPU to avoid
> confusion for programs that check for IIO buffer endianness.

Hi Andrew,

Well spotted. I'm sorry it is getting a bit messy because I posted a fix 
for this in a separate patch (see https://lkml.org/lkml/2015/12/12/131)

Using IIO_CPU seems an even better option, I did not know about this 
value and used IIO_LE.

Thanks!
Marc.




>
> I'll push this in a fixup patch later. Just wanted to give a
> heads up if you run into problems with some program.

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