Re: [PATCH 2/3] iio: adc: mxs-lradc: Add support for adc driver

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On 28/05/16 18:49, Ksenija Stanojević wrote:
> On Sun, May 1, 2016 at 6:38 PM, Jonathan Cameron <jic23@xxxxxxxxxx> wrote:
>> On 29/04/16 12:48, Ksenija Stanojevic wrote:
>>> Add mxs-lradc adc driver.
>>>
>>> Signed-off-by: Ksenija Stanojevic <ksenija.stanojevic@xxxxxxxxx>
>> Mostly looking good.  A few nitpicks and suggestions inline.
>>
>> Jonathan
>>> ---
>>>  drivers/iio/adc/Kconfig         |  37 +-
>>>  drivers/iio/adc/Makefile        |   1 +
>>>  drivers/iio/adc/mxs-lradc-adc.c | 832 ++++++++++++++++++++++++++++++++++++++++
>>>  3 files changed, 858 insertions(+), 12 deletions(-)
>>>  create mode 100644 drivers/iio/adc/mxs-lradc-adc.c
>>>
>>> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
>>> index 82c718c..50847b8 100644
>>> --- a/drivers/iio/adc/Kconfig
>>> +++ b/drivers/iio/adc/Kconfig
>>> @@ -233,6 +233,19 @@ config IMX7D_ADC
>>>         This driver can also be built as a module. If so, the module will be
>>>         called imx7d_adc.
>>>
>>> +config MXS_LRADC_ADC
>>> +     tristate "Freescale i.MX23/i.MX28 LRADC ADC"
>>> +     depends on MFD_MXS_LRADC
>>> +     select IIO_BUFFER
>>> +     select IIO_TRIGGERED_BUFFER
>>> +     help
>>> +       Say yes here to build support for the ADC functions of the
>>> +       i.MX23/i.MX28 LRADC. This includes general-purpose ADC readings,
>>> +       battery voltage measurement, and die temperature measurement.
>>> +
>>> +       This driver can also be built as a module. If so, the module will be
>>> +       called mxs-lradc-adc.
>>> +
>>>  config LP8788_ADC
>>>       tristate "LP8788 ADC driver"
>>>       depends on MFD_LP8788
>>> @@ -306,18 +319,18 @@ config MEN_Z188_ADC
>>>         called men_z188_adc.
>>>
>>>  config MXS_LRADC
>>> -        tristate "Freescale i.MX23/i.MX28 LRADC"
>>> -        depends on (ARCH_MXS || COMPILE_TEST) && HAS_IOMEM
>>> -        depends on INPUT
>>> -        select STMP_DEVICE
>>> -        select IIO_BUFFER
>>> -        select IIO_TRIGGERED_BUFFER
>>> -        help
>>> -          Say yes here to build support for i.MX23/i.MX28 LRADC convertor
>>> -          built into these chips.
>>> -
>>> -          To compile this driver as a module, choose M here: the
>>> -          module will be called mxs-lradc.
>>> +     tristate "Freescale i.MX23/i.MX28 LRADC"
>>> +     depends on (ARCH_MXS || COMPILE_TEST) && HAS_IOMEM
>>> +     depends on INPUT
>>> +     select STMP_DEVICE
>>> +     select IIO_BUFFER
>>> +     select IIO_TRIGGERED_BUFFER
>>> +     help
>>> +       Say yes here to build support for i.MX23/i.MX28 LRADC convertor
>>> +       built into these chips.
>>> +
>>> +       To compile this driver as a module, choose M here: the
>>> +       module will be called mxs-lradc.
>>>
>>>  config NAU7802
>>>       tristate "Nuvoton NAU7802 ADC driver"
>>> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
>>> index 0cb7921..ca7d6aa 100644
>>> --- a/drivers/iio/adc/Makefile
>>> +++ b/drivers/iio/adc/Makefile
>>> @@ -31,6 +31,7 @@ obj-$(CONFIG_MCP320X) += mcp320x.o
>>>  obj-$(CONFIG_MCP3422) += mcp3422.o
>>>  obj-$(CONFIG_MEN_Z188_ADC) += men_z188_adc.o
>>>  obj-$(CONFIG_MXS_LRADC) += mxs-lradc.o
>>> +obj-$(CONFIG_MXS_LRADC_ADC) += mxs-lradc-adc.o
>>>  obj-$(CONFIG_NAU7802) += nau7802.o
>>>  obj-$(CONFIG_PALMAS_GPADC) += palmas_gpadc.o
>>>  obj-$(CONFIG_QCOM_SPMI_IADC) += qcom-spmi-iadc.o
>>> diff --git a/drivers/iio/adc/mxs-lradc-adc.c b/drivers/iio/adc/mxs-lradc-adc.c
>>> new file mode 100644
>>> index 0000000..793c369
>>> --- /dev/null
>>> +++ b/drivers/iio/adc/mxs-lradc-adc.c
>>> @@ -0,0 +1,832 @@
>>> +/*
>>> + * Freescale MXS LRADC ADC driver
>>> + *
>>> + * Copyright (c) 2012 DENX Software Engineering, GmbH.
>>> + * Marek Vasut <marex@xxxxxxx>
>> You should probably add your own copyright as you are making substantial
>> improvements!
>>
>>> + *
>>> + * This program is free software; you can redistribute it and/or modify
>>> + * it under the terms of the GNU General Public License as published by
>>> + * the Free Software Foundation; either version 2 of the License, or
>>> + * (at your option) any later version.
>>> + *
>>> + * This program is distributed in the hope that it will be useful,
>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>>> + * GNU General Public License for more details.
>>> + */
>>> +
>>> +#include <linux/mfd/mxs-lradc.h>
>>> +#include <linux/module.h>
>>> +#include <linux/platform_device.h>
>>> +
>>> +#include <linux/iio/buffer.h>
>>> +#include <linux/iio/iio.h>
>>> +#include <linux/iio/trigger.h>
>>> +#include <linux/iio/trigger_consumer.h>
>>> +#include <linux/iio/triggered_buffer.h>
>>> +#include <linux/iio/sysfs.h>
>>> +
>>> +/*
>>> + * Make this runtime configurable if necessary. Currently, if the buffered mode
>>> + * is enabled, the LRADC takes LRADC_DELAY_TIMER_LOOP samples of data before
>>> + * triggering IRQ. The sampling happens every (LRADC_DELAY_TIMER_PER / 2000)
>>> + * seconds. The result is that the samples arrive every 500mS.
>>> + */
>>> +#define LRADC_DELAY_TIMER_PER        200
>>> +#define LRADC_DELAY_TIMER_LOOP       5
>>> +
>>> +#define VREF_MV_BASE 1850
>>> +
>>> +static const u32 mxs_lradc_adc_vref_mv[][LRADC_MAX_TOTAL_CHANS] = {
>>> +     [IMX23_LRADC] = {
>>> +             VREF_MV_BASE,           /* CH0 */
>>> +             VREF_MV_BASE,           /* CH1 */
>>> +             VREF_MV_BASE,           /* CH2 */
>>> +             VREF_MV_BASE,           /* CH3 */
>>> +             VREF_MV_BASE,           /* CH4 */
>>> +             VREF_MV_BASE,           /* CH5 */
>>> +             VREF_MV_BASE * 2,       /* CH6 VDDIO */
>>> +             VREF_MV_BASE * 4,       /* CH7 VBATT */
>>> +             VREF_MV_BASE,           /* CH8 Temp sense 0 */
>>> +             VREF_MV_BASE,           /* CH9 Temp sense 1 */
>>> +             VREF_MV_BASE,           /* CH10 */
>>> +             VREF_MV_BASE,           /* CH11 */
>>> +             VREF_MV_BASE,           /* CH12 USB_DP */
>>> +             VREF_MV_BASE,           /* CH13 USB_DN */
>>> +             VREF_MV_BASE,           /* CH14 VBG */
>>> +             VREF_MV_BASE * 4,       /* CH15 VDD5V */
>>> +     },
>>> +     [IMX28_LRADC] = {
>>> +             VREF_MV_BASE,           /* CH0 */
>>> +             VREF_MV_BASE,           /* CH1 */
>>> +             VREF_MV_BASE,           /* CH2 */
>>> +             VREF_MV_BASE,           /* CH3 */
>>> +             VREF_MV_BASE,           /* CH4 */
>>> +             VREF_MV_BASE,           /* CH5 */
>>> +             VREF_MV_BASE,           /* CH6 */
>>> +             VREF_MV_BASE * 4,       /* CH7 VBATT */
>>> +             VREF_MV_BASE,           /* CH8 Temp sense 0 */
>>> +             VREF_MV_BASE,           /* CH9 Temp sense 1 */
>>> +             VREF_MV_BASE * 2,       /* CH10 VDDIO */
>>> +             VREF_MV_BASE,           /* CH11 VTH */
>>> +             VREF_MV_BASE * 2,       /* CH12 VDDA */
>>> +             VREF_MV_BASE,           /* CH13 VDDD */
>>> +             VREF_MV_BASE,           /* CH14 VBG */
>>> +             VREF_MV_BASE * 4,       /* CH15 VDD5V */
>>> +     },
>>> +};
>>> +
>>> +enum mxs_lradc_divbytwo {
>>> +     MXS_LRADC_DIV_DISABLED = 0,
>>> +     MXS_LRADC_DIV_ENABLED,
>>> +};
>>> +
>>> +struct mxs_lradc_scale {
>>> +     unsigned int            integer;
>>> +     unsigned int            nano;
>>> +};
>>> +
>>> +struct mxs_lradc_adc {
>>> +     struct mxs_lradc        *lradc;
>>> +     struct device           *dev;
>>> +
>>> +     u32                     *buffer;
>>> +     struct iio_trigger      *trig;
>>> +     struct mutex            lock;
>>> +     struct completion       completion;
>>> +
>>> +     const u32               *vref_mv;
>>> +     struct mxs_lradc_scale  scale_avail[LRADC_MAX_TOTAL_CHANS][2];
>>> +     unsigned long           is_divided;
>>> +};
>>> +
>>> +/*
>>> + * Raw I/O operations
>>> + */
>>> +static int mxs_lradc_adc_read_single(struct iio_dev *iio_dev, int chan,
>>> +                                  int *val)
>>> +{
>>> +     struct mxs_lradc_adc *adc = iio_priv(iio_dev);
>>> +     struct mxs_lradc *lradc = adc->lradc;
>>> +     int ret;
>>> +
>>> +     /*
>>> +      * See if there is no buffered operation in progress. If there is simply
>>> +      * bail out. This can be improved to support both buffered and raw IO at
>>> +      * the same time, yet the code becomes horribly complicated. Therefore I
>>> +      * applied KISS principle here.
>> This is true in lots of devices!  Hence we often have a similar check.
>>> +      */
>>> +     ret = mutex_trylock(&adc->lock);
>>> +     if (!ret)
>>> +             return -EBUSY;
>> We have standard core infrastructure for this now that should do the trick.
>> iio_device_claim_direct_mode() etc.
>>> +
>>> +     reinit_completion(&adc->completion);
>>> +
>>> +     /*
>>> +      * No buffered operation in progress, map the channel and trigger it.
>>> +      * Virtual channel 0 is always used here as the others are always not
>>> +      * used if doing raw sampling.
>>> +      */
>>> +     if (lradc->soc == IMX28_LRADC)
>>> +             mxs_lradc_reg_clear(lradc, LRADC_CTRL1_LRADC_IRQ_EN(0),
>>> +                                 LRADC_CTRL1);
>>> +     mxs_lradc_reg_clear(lradc, 0x1, LRADC_CTRL0);
>>> +
>>> +     /* Enable / disable the divider per requirement */
>>> +     if (test_bit(chan, &adc->is_divided))
>>> +             mxs_lradc_reg_set(lradc,
>>> +                               1 << LRADC_CTRL2_DIVIDE_BY_TWO_OFFSET,
>>> +                               LRADC_CTRL2);
>>> +     else
>>> +             mxs_lradc_reg_clear(lradc,
>>> +                                 1 << LRADC_CTRL2_DIVIDE_BY_TWO_OFFSET,
>>> +                                 LRADC_CTRL2);
>>> +
>>> +     /* Clean the slot's previous content, then set new one. */
>>> +     mxs_lradc_reg_clear(lradc, LRADC_CTRL4_LRADCSELECT_MASK(0),
>>> +                         LRADC_CTRL4);
>>> +     mxs_lradc_reg_set(lradc, chan, LRADC_CTRL4);
>>> +
>>> +     mxs_lradc_reg_wrt(lradc, 0, LRADC_CH(0));
>>> +
>>> +     /* Enable the IRQ and start sampling the channel. */
>>> +     mxs_lradc_reg_set(lradc, LRADC_CTRL1_LRADC_IRQ_EN(0), LRADC_CTRL1);
>>> +     mxs_lradc_reg_set(lradc, BIT(0), LRADC_CTRL0);
>>> +
>>> +     /* Wait for completion on the channel, 1 second max. */
>>> +     ret = wait_for_completion_killable_timeout(&adc->completion, HZ);
>>> +     if (!ret)
>>> +             ret = -ETIMEDOUT;
>>> +     if (ret < 0)
>>> +             goto err;
>>> +
>>> +     /* Read the data. */
>>> +     *val = readl(lradc->base + LRADC_CH(0)) & LRADC_CH_VALUE_MASK;
>>> +     ret = IIO_VAL_INT;
>>> +
>>> +err:
>>> +     mxs_lradc_reg_clear(lradc, LRADC_CTRL1_LRADC_IRQ_EN(0), LRADC_CTRL1);
>>> +
>>> +     mutex_unlock(&adc->lock);
>>> +
>>> +     return ret;
>>> +}
>>> +
>>> +static int mxs_lradc_adc_read_temp(struct iio_dev *iio_dev, int *val)
>>> +{
>>> +     int ret, min, max;
>>> +
>>> +     ret = mxs_lradc_adc_read_single(iio_dev, 8, &min);
>>> +     if (ret != IIO_VAL_INT)
>>> +             return ret;
>>> +
>>> +     ret = mxs_lradc_adc_read_single(iio_dev, 9, &max);
>>> +     if (ret != IIO_VAL_INT)
>>> +             return ret;
>>> +
>>> +     *val = max - min;
>>> +
>>> +     return IIO_VAL_INT;
>>> +}
>>> +
>>> +static int mxs_lradc_adc_read_raw(struct iio_dev *iio_dev,
>>> +                           const struct iio_chan_spec *chan,
>>> +                           int *val, int *val2, long m)
>>> +{
>>> +     struct mxs_lradc_adc *adc = iio_priv(iio_dev);
>>> +
>>> +     switch (m) {
>>> +     case IIO_CHAN_INFO_RAW:
>>> +             if (chan->type == IIO_TEMP)
>>> +                     return mxs_lradc_adc_read_temp(iio_dev, val);
>>> +
>>> +             return mxs_lradc_adc_read_single(iio_dev, chan->channel, val);
>>> +
>>> +     case IIO_CHAN_INFO_SCALE:
>>> +             if (chan->type == IIO_TEMP) {
>>> +                     /* From the datasheet, we have to multiply by 1.012 and
>>> +                      * divide by 4
>>> +                      */
>>> +                     *val = 0;
>>> +                     *val2 = 253000;
>>> +                     return IIO_VAL_INT_PLUS_MICRO;
>>> +             }
>>> +
>>> +             *val = adc->vref_mv[chan->channel];
>>> +             *val2 = chan->scan_type.realbits -
>>> +                     test_bit(chan->channel, &adc->is_divided);
>> blank line here as you have done elsewhere...
>>> +             return IIO_VAL_FRACTIONAL_LOG2;
>>> +
>>> +     case IIO_CHAN_INFO_OFFSET:
>>> +             if (chan->type == IIO_TEMP) {
>> standard multiline comment syntax please.  Please fix this throughout.
>>
>> /*
>>  * The ...
>>> +                     /* The calculated value from the ADC is in Kelvin, we
>>> +                      * want Celsius for hwmon so the offset is -273.15
>>> +                      * The offset is applied before scaling so it is
>>> +                      * actually -213.15 * 4 / 1.012 = -1079.644268
>>> +                      */
>>> +                     *val = -1079;
>>> +                     *val2 = 644268;
>>> +
>>> +                     return IIO_VAL_INT_PLUS_MICRO;
>>> +             }
>>> +
>>> +             return -EINVAL;
>>> +
>>> +     default:
>>> +             break;
>>> +     }
>>> +
>>> +     return -EINVAL;
>>> +}
>>> +
>>> +static int mxs_lradc_adc_write_raw(struct iio_dev *iio_dev,
>>> +                                const struct iio_chan_spec *chan,
>>> +                                int val, int val2, long m)
>>> +{
>>> +     struct mxs_lradc_adc *adc = iio_priv(iio_dev);
>>> +     struct mxs_lradc_scale *scale_avail =
>>> +                     adc->scale_avail[chan->channel];
>>> +     int ret;
>>> +
>>> +     ret = mutex_trylock(&adc->lock);
>>> +     if (!ret)
>>> +             return -EBUSY;
>>> +
>>> +     switch (m) {
>>> +     case IIO_CHAN_INFO_SCALE:
>>> +             ret = -EINVAL;
>>> +             if (val == scale_avail[MXS_LRADC_DIV_DISABLED].integer &&
>>> +                 val2 == scale_avail[MXS_LRADC_DIV_DISABLED].nano) {
>>> +                     /* divider by two disabled */
>>> +                     clear_bit(chan->channel, &adc->is_divided);
>>> +                     ret = 0;
>>> +             } else if (val == scale_avail[MXS_LRADC_DIV_ENABLED].integer &&
>>> +                        val2 == scale_avail[MXS_LRADC_DIV_ENABLED].nano) {
>>> +                     /* divider by two enabled */
>>> +                     set_bit(chan->channel, &adc->is_divided);
>>> +                     ret = 0;
>>> +             }
>>> +
>>> +             break;
>>> +     default:
>>> +             ret = -EINVAL;
>>> +             break;
>>> +     }
>>> +
>>> +     mutex_unlock(&adc->lock);
>>> +
>>> +     return ret;
>>> +}
>>> +
>>> +static int mxs_lradc_adc_write_raw_get_fmt(struct iio_dev *iio_dev,
>>> +                                        const struct iio_chan_spec *chan,
>>> +                                        long m)
>>> +{
>>> +     return IIO_VAL_INT_PLUS_NANO;
>>> +}
>>> +
>>> +static ssize_t mxs_lradc_adc_show_scale_avail_ch(struct device *dev,
>>> +                                              struct device_attribute *attr,
>>> +                                              char *buf,
>>> +                                              int ch)
>>> +{
>>> +     struct iio_dev *iio = dev_to_iio_dev(dev);
>>> +     struct mxs_lradc_adc *adc = iio_priv(iio);
>>> +     int i, len = 0;
>>> +
>>> +     for (i = 0; i < ARRAY_SIZE(adc->scale_avail[ch]); i++)
>>> +             len += sprintf(buf + len, "%u.%09u ",
>>> +                            adc->scale_avail[ch][i].integer,
>>> +                            adc->scale_avail[ch][i].nano);
>>> +
>>> +     len += sprintf(buf + len, "\n");
>>> +
>>> +     return len;
>>> +}
>>> +
>> I'm unconvinced this wrapper adds anything...
>>> +static ssize_t mxs_lradc_adc_show_scale_avail(struct device *dev,
>>> +                                           struct device_attribute *attr,
>>> +                                           char *buf)
>>> +{
>>> +     struct iio_dev_attr *iio_attr = to_iio_dev_attr(attr);
>>> +
>>> +     return mxs_lradc_adc_show_scale_avail_ch(dev, attr, buf,
>>> +                                              iio_attr->address);
>>> +}
>>> +
>>> +#define SHOW_SCALE_AVAILABLE_ATTR(ch)                                        \
>>> +static IIO_DEVICE_ATTR(in_voltage##ch##_scale_available, S_IRUGO,    \
>>> +                    mxs_lradc_adc_show_scale_avail, NULL, ch)
>>> +
>>> +SHOW_SCALE_AVAILABLE_ATTR(0);
>>> +SHOW_SCALE_AVAILABLE_ATTR(1);
>>> +SHOW_SCALE_AVAILABLE_ATTR(2);
>>> +SHOW_SCALE_AVAILABLE_ATTR(3);
>>> +SHOW_SCALE_AVAILABLE_ATTR(4);
>>> +SHOW_SCALE_AVAILABLE_ATTR(5);
>>> +SHOW_SCALE_AVAILABLE_ATTR(6);
>>> +SHOW_SCALE_AVAILABLE_ATTR(7);
>>> +SHOW_SCALE_AVAILABLE_ATTR(10);
>>> +SHOW_SCALE_AVAILABLE_ATTR(11);
>>> +SHOW_SCALE_AVAILABLE_ATTR(12);
>>> +SHOW_SCALE_AVAILABLE_ATTR(13);
>>> +SHOW_SCALE_AVAILABLE_ATTR(14);
>>> +SHOW_SCALE_AVAILABLE_ATTR(15);
>>> +
>>> +static struct attribute *mxs_lradc_adc_attributes[] = {
>>> +     &iio_dev_attr_in_voltage0_scale_available.dev_attr.attr,
>>> +     &iio_dev_attr_in_voltage1_scale_available.dev_attr.attr,
>>> +     &iio_dev_attr_in_voltage2_scale_available.dev_attr.attr,
>>> +     &iio_dev_attr_in_voltage3_scale_available.dev_attr.attr,
>>> +     &iio_dev_attr_in_voltage4_scale_available.dev_attr.attr,
>>> +     &iio_dev_attr_in_voltage5_scale_available.dev_attr.attr,
>>> +     &iio_dev_attr_in_voltage6_scale_available.dev_attr.attr,
>>> +     &iio_dev_attr_in_voltage7_scale_available.dev_attr.attr,
>>> +     &iio_dev_attr_in_voltage10_scale_available.dev_attr.attr,
>>> +     &iio_dev_attr_in_voltage11_scale_available.dev_attr.attr,
>>> +     &iio_dev_attr_in_voltage12_scale_available.dev_attr.attr,
>>> +     &iio_dev_attr_in_voltage13_scale_available.dev_attr.attr,
>>> +     &iio_dev_attr_in_voltage14_scale_available.dev_attr.attr,
>>> +     &iio_dev_attr_in_voltage15_scale_available.dev_attr.attr,
>>> +     NULL
>>> +};
>>> +
>>> +static const struct attribute_group mxs_lradc_adc_attribute_group = {
>>> +     .attrs = mxs_lradc_adc_attributes,
>>> +};
>>> +
>>> +static const struct iio_info mxs_lradc_adc_iio_info = {
>>> +     .driver_module          = THIS_MODULE,
>>> +     .read_raw               = mxs_lradc_adc_read_raw,
>>> +     .write_raw              = mxs_lradc_adc_write_raw,
>>> +     .write_raw_get_fmt      = mxs_lradc_adc_write_raw_get_fmt,
>>> +     .attrs                  = &mxs_lradc_adc_attribute_group,
>>> +};
>>> +
>>> +/*
>>> + * IRQ Handling
>>> + */
>> Single line comment syntax preferred.
>>> +static irqreturn_t mxs_lradc_adc_handle_irq(int irq, void *data)
>>> +{
>>> +     struct iio_dev *iio = data;
>>> +     struct mxs_lradc_adc *adc = iio_priv(iio);
>>> +     struct mxs_lradc *lradc = adc->lradc;
>>> +     unsigned long reg = readl(lradc->base + LRADC_CTRL1);
>>> +
>>> +     if (!(reg & mxs_lradc_irq_mask(lradc)))
>>> +             return IRQ_NONE;
>>> +
>>> +     if (iio_buffer_enabled(iio)) {
>>> +             if (reg & lradc->buffer_vchans)
>>> +                     iio_trigger_poll(iio->trig);
>>> +     } else if (reg & LRADC_CTRL1_LRADC_IRQ(0)) {
>>> +             complete(&adc->completion);
>>> +     }
>>> +
>>> +     mxs_lradc_reg_clear(lradc, reg & mxs_lradc_irq_mask(lradc),
>>> +                         LRADC_CTRL1);
>>> +
>>> +     return IRQ_HANDLED;
>>> +}
>>> +
>>> +/*
>>> + * Trigger handling
>> Single line comment - Clearly it's kind of more of a heading but I'd rather
>> not deal with the inevitable patch converting it to the standard single line
>> format!
>>> + */
>>> +static irqreturn_t mxs_lradc_adc_trigger_handler(int irq, void *p)
>>> +{
>>> +     struct iio_poll_func *pf = p;
>>> +     struct iio_dev *iio = pf->indio_dev;
>>> +     struct mxs_lradc_adc *adc = iio_priv(iio);
>>> +     const u32 chan_value = LRADC_CH_ACCUMULATE |
>>> +             ((LRADC_DELAY_TIMER_LOOP - 1) << LRADC_CH_NUM_SAMPLES_OFFSET);
>>> +     unsigned int i, j = 0;
>>> +
>>> +     for_each_set_bit(i, iio->active_scan_mask, LRADC_MAX_TOTAL_CHANS) {
>>> +             adc->buffer[j] = readl(adc->lradc->base + LRADC_CH(j));
>>> +             mxs_lradc_reg_wrt(adc->lradc, chan_value, LRADC_CH(j));
>>> +             adc->buffer[j] &= LRADC_CH_VALUE_MASK;
>>> +             adc->buffer[j] /= LRADC_DELAY_TIMER_LOOP;
>>> +             j++;
>>> +     }
>>> +
>>> +     iio_push_to_buffers_with_timestamp(iio, adc->buffer, pf->timestamp);
>>> +
>>> +     iio_trigger_notify_done(iio->trig);
>>> +
>>> +     return IRQ_HANDLED;
>>> +}
>>> +
>>> +static int mxs_lradc_adc_configure_trigger(struct iio_trigger *trig, bool state)
>>> +{
>>> +     struct iio_dev *iio = iio_trigger_get_drvdata(trig);
>>> +     struct mxs_lradc_adc *adc = iio_priv(iio);
>>> +     const u32 st = state ? STMP_OFFSET_REG_SET : STMP_OFFSET_REG_CLR;
>>> +
>>> +     mxs_lradc_reg_wrt(adc->lradc, LRADC_DELAY_KICK, LRADC_DELAY(0) + st);
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +static const struct iio_trigger_ops mxs_lradc_adc_trigger_ops = {
>>> +     .owner = THIS_MODULE,
>>> +     .set_trigger_state = &mxs_lradc_adc_configure_trigger,
>>> +};
>>> +
>>> +static int mxs_lradc_adc_trigger_init(struct iio_dev *iio)
>>> +{
>>> +     int ret;
>>> +     struct iio_trigger *trig;
>>> +     struct mxs_lradc_adc *adc = iio_priv(iio);
>>> +
>> Could simplify things ever so slightly by using devm_iio_trigger_alloc if you
>> were to reorder the trigger init to be before the buffer setup (which I think
>> should be fine).  Perhaps it is not worth the hassle...
>>> +     trig = iio_trigger_alloc("%s-dev%i", iio->name, iio->id);
>>> +     if (!trig)
>>> +             return -ENOMEM;
>>> +
>>> +     trig->dev.parent = adc->dev;
>>> +     iio_trigger_set_drvdata(trig, iio);
>>> +     trig->ops = &mxs_lradc_adc_trigger_ops;
>>> +
>>> +     ret = iio_trigger_register(trig);
>>> +     if (ret) {
>>> +             iio_trigger_free(trig);
>>> +             return ret;
>>> +     }
>>> +
>>> +     adc->trig = trig;
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +static void mxs_lradc_adc_trigger_remove(struct iio_dev *iio)
>>> +{
>>> +     struct mxs_lradc_adc *adc = iio_priv(iio);
>>> +
>>> +     iio_trigger_unregister(adc->trig);
>>> +     iio_trigger_free(adc->trig);
>>> +}
>>> +
>>> +static int mxs_lradc_adc_buffer_preenable(struct iio_dev *iio)
>>> +{
>>> +     struct mxs_lradc_adc *adc = iio_priv(iio);
>>> +     struct mxs_lradc *lradc = adc->lradc;
>>> +     int ret = 0, chan, ofs = 0;
>>> +     unsigned long enable = 0;
>>> +     u32 ctrl4_set = 0;
>>> +     u32 ctrl4_clr = 0;
>>> +     u32 ctrl1_irq = 0;
>>> +     const u32 chan_value = LRADC_CH_ACCUMULATE |
>>> +             ((LRADC_DELAY_TIMER_LOOP - 1) << LRADC_CH_NUM_SAMPLES_OFFSET);
>>> +     const int len = bitmap_weight(iio->active_scan_mask,
>>> +                     LRADC_MAX_TOTAL_CHANS);
>>> +
>>> +     if (!len)
>>> +             return -EINVAL;
>>> +
>>> +     /*
>>> +      * Lock the driver so raw access can not be done during buffered
>>> +      * operation. This simplifies the code a lot.
>>> +      */
>>> +     ret = mutex_trylock(&adc->lock);
>>> +     if (!ret)
>>> +             return -EBUSY;
>> Hmm. could this use iio_dev->mlock?  That is what that particular lock is
>> for and it has nice wrapper functions to make it clear.
>>> +
>>> +     adc->buffer = kmalloc_array(len, sizeof(*adc->buffer), GFP_KERNEL);
>>> +     if (!adc->buffer) {
>>> +             ret = -ENOMEM;
>>> +             goto err_mem;
>>> +     }
>> I wonder if it's worth the hassel of doing this dynamically.  Maybe just have a
>> buffer that is big enough to take all possibilities as part of the adc
>> struct?
>>> +
>>> +     if (lradc->soc == IMX28_LRADC)
>>> +             mxs_lradc_reg_clear(
>>> +                     lradc,
>>> +                     lradc->buffer_vchans << LRADC_CTRL1_LRADC_IRQ_EN_OFFSET,
>>> +                     LRADC_CTRL1);
>>> +     mxs_lradc_reg_clear(lradc, lradc->buffer_vchans, LRADC_CTRL0);
>>> +
>>> +     for_each_set_bit(chan, iio->active_scan_mask, LRADC_MAX_TOTAL_CHANS) {
>>> +             ctrl4_set |= chan << LRADC_CTRL4_LRADCSELECT_OFFSET(ofs);
>>> +             ctrl4_clr |= LRADC_CTRL4_LRADCSELECT_MASK(ofs);
>>> +             ctrl1_irq |= LRADC_CTRL1_LRADC_IRQ_EN(ofs);
>>> +             mxs_lradc_reg_wrt(lradc, chan_value, LRADC_CH(ofs));
>>> +             bitmap_set(&enable, ofs, 1);
>>> +             ofs++;
>>> +     }
>>> +
>>> +     mxs_lradc_reg_clear(lradc, LRADC_DELAY_TRIGGER_LRADCS_MASK |
>>> +                         LRADC_DELAY_KICK, LRADC_DELAY(0));
>>> +     mxs_lradc_reg_clear(lradc, ctrl4_clr, LRADC_CTRL4);
>>> +     mxs_lradc_reg_set(lradc, ctrl4_set, LRADC_CTRL4);
>>> +     mxs_lradc_reg_set(lradc, ctrl1_irq, LRADC_CTRL1);
>>> +     mxs_lradc_reg_set(lradc, enable << LRADC_DELAY_TRIGGER_LRADCS_OFFSET,
>>> +                       LRADC_DELAY(0));
>>> +
>>> +     return 0;
>>> +
>>> +err_mem:
>>> +     mutex_unlock(&adc->lock);
>>> +     return ret;
>>> +}
>>> +
>>> +static int mxs_lradc_adc_buffer_postdisable(struct iio_dev *iio)
>>> +{
>>> +     struct mxs_lradc_adc *adc = iio_priv(iio);
>>> +     struct mxs_lradc *lradc = adc->lradc;
>>> +
>>> +     mxs_lradc_reg_clear(lradc, LRADC_DELAY_TRIGGER_LRADCS_MASK |
>>> +                         LRADC_DELAY_KICK, LRADC_DELAY(0));
>>> +
>>> +     mxs_lradc_reg_clear(lradc, lradc->buffer_vchans, LRADC_CTRL0);
>>> +     if (lradc->soc == IMX28_LRADC)
>>> +             mxs_lradc_reg_clear(
>>> +                     lradc,
>>> +                     lradc->buffer_vchans << LRADC_CTRL1_LRADC_IRQ_EN_OFFSET,
>>> +                     LRADC_CTRL1);
>>> +
>>> +     kfree(adc->buffer);
>>> +     mutex_unlock(&adc->lock);
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +static bool mxs_lradc_adc_validate_scan_mask(struct iio_dev *iio,
>>> +                                          const unsigned long *mask)
>>> +{
>>> +     struct mxs_lradc_adc *adc = iio_priv(iio);
>>> +     struct mxs_lradc *lradc = adc->lradc;
>>> +     const int map_chans = bitmap_weight(mask, LRADC_MAX_TOTAL_CHANS);
>>> +     int rsvd_chans = 0;
>>> +     unsigned long rsvd_mask = 0;
>>> +
>>> +     if (lradc->use_touchbutton)
>>> +             rsvd_mask |= CHAN_MASK_TOUCHBUTTON;
>>> +     if (lradc->use_touchscreen == MXS_LRADC_TOUCHSCREEN_4WIRE)
>>> +             rsvd_mask |= CHAN_MASK_TOUCHSCREEN_4WIRE;
>>> +     if (lradc->use_touchscreen == MXS_LRADC_TOUCHSCREEN_5WIRE)
>>> +             rsvd_mask |= CHAN_MASK_TOUCHSCREEN_5WIRE;
>>> +
>>> +     if (lradc->use_touchbutton)
>>> +             rsvd_chans++;
>>> +     if (lradc->use_touchscreen)
>>> +             rsvd_chans += 2;
>>> +
>>> +     /* Test for attempts to map channels with special mode of operation. */
>>> +     if (bitmap_intersects(mask, &rsvd_mask, LRADC_MAX_TOTAL_CHANS))
>>> +             return false;
>>> +
>>> +     /* Test for attempts to map more channels then available slots. */
>>> +     if (map_chans + rsvd_chans > LRADC_MAX_MAPPED_CHANS)
>>> +             return false;
>>> +
>>> +     return true;
>>> +}
>>> +
>>> +static const struct iio_buffer_setup_ops mxs_lradc_adc_buffer_ops = {
>>> +     .preenable = &mxs_lradc_adc_buffer_preenable,
>>> +     .postenable = &iio_triggered_buffer_postenable,
>>> +     .predisable = &iio_triggered_buffer_predisable,
>>> +     .postdisable = &mxs_lradc_adc_buffer_postdisable,
>>> +     .validate_scan_mask = &mxs_lradc_adc_validate_scan_mask,
>>> +};
>>> +
>>> +/*
>>> + * Driver initialization
>>> + */
>>> +
>>> +#define MXS_ADC_CHAN(idx, chan_type, name) {                 \
>>> +     .type = (chan_type),                                    \
>>> +     .indexed = 1,                                           \
>>> +     .scan_index = (idx),                                    \
>>> +     .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |          \
>>> +                           BIT(IIO_CHAN_INFO_SCALE),         \
>>> +     .channel = (idx),                                       \
>>> +     .address = (idx),                                       \
>>> +     .scan_type = {                                          \
>>> +             .sign = 'u',                                    \
>>> +             .realbits = LRADC_RESOLUTION,                   \
>>> +             .storagebits = 32,                              \
>>> +     },                                                      \
>>> +     .datasheet_name = (name),                               \
>>> +}
>>> +
>>> +static const struct iio_chan_spec mx23_lradc_chan_spec[] = {
>>> +     MXS_ADC_CHAN(0, IIO_VOLTAGE, "LRADC0"),
>>> +     MXS_ADC_CHAN(1, IIO_VOLTAGE, "LRADC1"),
>>> +     MXS_ADC_CHAN(2, IIO_VOLTAGE, "LRADC2"),
>>> +     MXS_ADC_CHAN(3, IIO_VOLTAGE, "LRADC3"),
>>> +     MXS_ADC_CHAN(4, IIO_VOLTAGE, "LRADC4"),
>>> +     MXS_ADC_CHAN(5, IIO_VOLTAGE, "LRADC5"),
>>> +     MXS_ADC_CHAN(6, IIO_VOLTAGE, "VDDIO"),
>>> +     MXS_ADC_CHAN(7, IIO_VOLTAGE, "VBATT"),
>>> +     /* Combined Temperature sensors */
>>> +     {
>>> +             .type = IIO_TEMP,
>>> +             .indexed = 1,
>>> +             .scan_index = 8,
>>> +             .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
>>> +                                   BIT(IIO_CHAN_INFO_OFFSET) |
>>> +                                   BIT(IIO_CHAN_INFO_SCALE),
>>> +             .channel = 8,
>>> +             .scan_type = {.sign = 'u', .realbits = 18, .storagebits = 32,},
>>> +             .datasheet_name = "TEMP_DIE",
>>> +     },
>>> +     /* Hidden channel to keep indexes */
>>> +     {
>>> +             .type = IIO_TEMP,
>>> +             .indexed = 1,
>>> +             .scan_index = -1,
>>> +             .channel = 9,
>>> +     },
>>> +     MXS_ADC_CHAN(10, IIO_VOLTAGE, NULL),
>>> +     MXS_ADC_CHAN(11, IIO_VOLTAGE, NULL),
>>> +     MXS_ADC_CHAN(12, IIO_VOLTAGE, "USB_DP"),
>>> +     MXS_ADC_CHAN(13, IIO_VOLTAGE, "USB_DN"),
>>> +     MXS_ADC_CHAN(14, IIO_VOLTAGE, "VBG"),
>>> +     MXS_ADC_CHAN(15, IIO_VOLTAGE, "VDD5V"),
>>> +};
>>> +
>>> +static const struct iio_chan_spec mx28_lradc_chan_spec[] = {
>>> +     MXS_ADC_CHAN(0, IIO_VOLTAGE, "LRADC0"),
>>> +     MXS_ADC_CHAN(1, IIO_VOLTAGE, "LRADC1"),
>>> +     MXS_ADC_CHAN(2, IIO_VOLTAGE, "LRADC2"),
>>> +     MXS_ADC_CHAN(3, IIO_VOLTAGE, "LRADC3"),
>>> +     MXS_ADC_CHAN(4, IIO_VOLTAGE, "LRADC4"),
>>> +     MXS_ADC_CHAN(5, IIO_VOLTAGE, "LRADC5"),
>>> +     MXS_ADC_CHAN(6, IIO_VOLTAGE, "LRADC6"),
>>> +     MXS_ADC_CHAN(7, IIO_VOLTAGE, "VBATT"),
>>> +     /* Combined Temperature sensors */
>>> +     {
>>> +             .type = IIO_TEMP,
>>> +             .indexed = 1,
>>> +             .scan_index = 8,
>>> +             .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
>>> +                                   BIT(IIO_CHAN_INFO_OFFSET) |
>>> +                                   BIT(IIO_CHAN_INFO_SCALE),
>>> +             .channel = 8,
>>> +             .scan_type = {.sign = 'u', .realbits = 18, .storagebits = 32,},
>>> +             .datasheet_name = "TEMP_DIE",
>>> +     },
>>> +     /* Hidden channel to keep indexes */
>>> +     {
>>> +             .type = IIO_TEMP,
>>> +             .indexed = 1,
>>> +             .scan_index = -1,
>>> +             .channel = 9,
>>> +     },
>>> +     MXS_ADC_CHAN(10, IIO_VOLTAGE, "VDDIO"),
>>> +     MXS_ADC_CHAN(11, IIO_VOLTAGE, "VTH"),
>>> +     MXS_ADC_CHAN(12, IIO_VOLTAGE, "VDDA"),
>>> +     MXS_ADC_CHAN(13, IIO_VOLTAGE, "VDDD"),
>>> +     MXS_ADC_CHAN(14, IIO_VOLTAGE, "VBG"),
>>> +     MXS_ADC_CHAN(15, IIO_VOLTAGE, "VDD5V"),
>>> +};
>>> +
>>> +static void mxs_lradc_adc_hw_init(struct mxs_lradc_adc *adc)
>>> +{
>>> +     struct mxs_lradc *lradc = adc->lradc;
>>> +
>>> +     /* The ADC always uses DELAY CHANNEL 0. */
>>> +     const u32 adc_cfg =
>>> +             (1 << (LRADC_DELAY_TRIGGER_DELAYS_OFFSET + 0)) |
>>> +             (LRADC_DELAY_TIMER_PER << LRADC_DELAY_DELAY_OFFSET);
>>> +
>>> +     /* Configure DELAY CHANNEL 0 for generic ADC sampling. */
>>> +     mxs_lradc_reg_wrt(lradc, adc_cfg, LRADC_DELAY(0));
>>> +
>>> +     /* Start internal temperature sensing. */
>> We start internal temperature sensing, do we ever want to stop it?
> 
> According to manual[1] there is no need to:
> To use the internal die temperature sensor,
> HW_LRADC_CTRL2_TEMPSENSE_PWD should be cleared. (This bit can be left
> cleared after power up. There is no need to toggle it on and off.)
Fair enough - perhaps a note here to make that clear to future readers?
> 
>>> +     mxs_lradc_reg_wrt(lradc, 0, LRADC_CTRL2);
>>> +}
>>> +
>>> +static void mxs_lradc_adc_hw_stop(struct mxs_lradc_adc *adc)
>>> +{
>>> +     mxs_lradc_reg_wrt(adc->lradc, 0, LRADC_DELAY(0));
>>> +}
>>> +
>>> +static int mxs_lradc_adc_probe(struct platform_device *pdev)
>>> +{
>>> +     struct device *dev = &pdev->dev;
>>> +     struct mxs_lradc *lradc = dev_get_platdata(dev);
>>> +     struct mxs_lradc_adc *adc;
>>> +     struct iio_dev *iio;
>>> +     int ret, i, s;
>>> +     u64 scale_uv;
>>> +
>>> +     /* Allocate the IIO device. */
>>> +     iio = devm_iio_device_alloc(dev, sizeof(*adc));
>>> +     if (!iio) {
>>> +             dev_err(dev, "Failed to allocate IIO device\n");
>>> +             return -ENOMEM;
>>> +     }
>>> +
>>> +     adc = iio_priv(iio);
>>> +     adc->lradc = lradc;
>>> +     adc->dev = dev;
>>> +
>>> +     init_completion(&adc->completion);
>>> +     mutex_init(&adc->lock);
>>> +
>>> +     for (i = 0; i < lradc->irq_count; i++) {
>>> +             ret = devm_request_irq(dev, lradc->irq[i],
>>> +                                    mxs_lradc_adc_handle_irq,
>>> +                                    IRQF_SHARED, lradc->irq_name[i], iio);
>>> +             if (ret)
>>> +                     return ret;
>> This seems to be getting a whole load of irq's whether or not they are actually
>> going to be used by the ADC?  Aren't some of these going to be typically used by
>> the touchscreen?
>>> +     }
>>> +
>>> +     platform_set_drvdata(pdev, iio);
>>> +
>>> +     iio->name = pdev->name;
>>> +     iio->dev.parent = dev;
>>> +     iio->dev.of_node = dev->parent->of_node;
>>> +     iio->info = &mxs_lradc_adc_iio_info;
>>> +     iio->modes = INDIO_DIRECT_MODE;
>>> +     iio->masklength = LRADC_MAX_TOTAL_CHANS;
>>> +
>>> +     if (lradc->soc == IMX23_LRADC) {
>>> +             iio->channels = mx23_lradc_chan_spec;
>>> +             iio->num_channels = ARRAY_SIZE(mx23_lradc_chan_spec);
>>> +     } else {
>>> +             iio->channels = mx28_lradc_chan_spec;
>>> +             iio->num_channels = ARRAY_SIZE(mx28_lradc_chan_spec);
>>> +     }
>>> +
>>> +     ret = iio_triggered_buffer_setup(iio, &iio_pollfunc_store_time,
>>> +                                      &mxs_lradc_adc_trigger_handler,
>>> +                                      &mxs_lradc_adc_buffer_ops);
>>> +     if (ret)
>>> +             return ret;
>>> +
>>> +     ret = mxs_lradc_adc_trigger_init(iio);
>>> +     if (ret)
>>> +             goto err_trig;
>>> +
>>> +     adc->vref_mv = mxs_lradc_adc_vref_mv[lradc->soc];
>>> +
>>> +     /* Populate available ADC input ranges */
>>> +     for (i = 0; i < LRADC_MAX_TOTAL_CHANS; i++) {
>>> +             for (s = 0; s < ARRAY_SIZE(adc->scale_avail[i]); s++) {
>>> +                     /*
>>> +                      * [s=0] = optional divider by two disabled (default)
>>> +                      * [s=1] = optional divider by two enabled
>>> +                      *
>>> +                      * The scale is calculated by doing:
>>> +                      *   Vref >> (realbits - s)
>>> +                      * which multiplies by two on the second component
>>> +                      * of the array.
>>> +                      */
>>> +                     scale_uv = ((u64)adc->vref_mv[i] * 100000000) >>
>>> +                                (LRADC_RESOLUTION - s);
>>> +                     adc->scale_avail[i][s].nano =
>>> +                                     do_div(scale_uv, 100000000) * 10;
>>> +                     adc->scale_avail[i][s].integer = scale_uv;
>>> +             }
>>> +     }
>>> +
>>> +     /* Configure the hardware. */
>>> +     mxs_lradc_adc_hw_init(adc);
>>> +
>>> +     /* Register IIO device. */
>>> +     ret = iio_device_register(iio);
>>> +     if (ret) {
>>> +             dev_err(dev, "Failed to register IIO device\n");
>>> +             goto err_dev;
>>> +     }
>>> +
>>> +     return 0;
>>> +
>>> +err_dev:
>>> +     mxs_lradc_adc_hw_stop(adc);
>>> +     mxs_lradc_adc_trigger_remove(iio);
>>> +err_trig:
>>> +     iio_triggered_buffer_cleanup(iio);
>>> +     return ret;
>>> +}
>>> +
>>> +static int mxs_lradc_adc_remove(struct platform_device *pdev)
>>> +{
>>> +     struct iio_dev *iio = platform_get_drvdata(pdev);
>>> +     struct mxs_lradc_adc *adc = iio_priv(iio);
>>> +
>>> +     iio_device_unregister(iio);
>>> +     mxs_lradc_adc_hw_stop(adc);
>>> +     mxs_lradc_adc_trigger_remove(iio);
>>> +     iio_triggered_buffer_cleanup(iio);
>>> +
>>> +     return 0;
>>> +}
>>> +
>>> +static struct platform_driver mxs_lradc_adc_driver = {
>>> +     .driver = {
>>> +             .name   = DRIVER_NAME_ADC,
>>> +     },
>>> +     .probe  = mxs_lradc_adc_probe,
>>> +     .remove = mxs_lradc_adc_remove,
>>> +};
>>> +
>>> +module_platform_driver(mxs_lradc_adc_driver);
>>> +
>>> +MODULE_AUTHOR("Marek Vasut <marex@xxxxxxx>");
>>> +MODULE_DESCRIPTION("Freescale MXS LRADC driver general purpose ADC driver");
>>> +MODULE_LICENSE("GPL v2");
>>> +MODULE_ALIAS("platform:" DRIVER_NAME_ADC);
>>> +
>> Bonus blank line at end of file...
>>> +
>>>
>>
> [1] http://cache.freescale.com/files/dsp/doc/ref_manual/MCIMX28RM.pdf
> 

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