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 12:09:02 -0600
From:	"Andrew F. Davis" <afd@...com>
To:	Marc Titinger <mtitinger@...libre.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 12/16/2015 11:54 AM, Marc Titinger wrote:
> 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)
>

Ah, wasn't following that.

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

Which will give incorrect results on BE systems, I'll wait till the dust settles for this
driver and push some more small fixups a bit later.

> Thanks!
> Marc.
>
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