Re: [PATCH v4 1/1] iio: stx104: Add IIO support for the ADC channels

From: Jonathan Cameron
Date: Sun Aug 21 2016 - 15:39:08 EST

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On 25/07/16 18:54, William Breathitt Gray wrote:
> The Apex Embedded Systems STX104 features 16 channels of single-ended (8
> channels of true differential) 16-bit analog input. Differential input
> configuration may be selected via a physical jumper on the device.
> Similarly, input polarity (unipolar/bipolar) is configured via a
> physical jumper on the device.
>
> Input gain selection is available to the user via software, thus
> allowing eight possible input ranges: +-10V, +-5V, +-2.5V, +-1.25V,
> 0 to 10V, 0 to 5V, 0 to 2.5V, and 0 to 1.25V. Four input gain
> configurations are supported: x1, x2, x4, and x8.
>
> This ADC resolution is 16-bits (1/65536 of full scale). Analog input
> samples are taken on software trigger; neither FIFO sampling nor
> interrupt triggering is supported by this driver.
>
> The Apex Embedded Systems STX104 is primarily an analog-to-digital
> converter device. The STX104 IIO driver was initially placed in the DAC
> directory because only the DAC portion of the STX104 was supported at
> the time. Now that ADC support has been added to the STX104 IIO driver,
> the driver should be moved to the more appropriate ADC directory.
>
> Signed-off-by: William Breathitt Gray <vilhelm.gray@xxxxxxxxx>
Hi William,

I'd missed the odd use of an output channel to control scale.
I'm guessing this is because we are looking at actual control of a front
end separate amplifier on the board? However as far as the driver is
confirmed this is no different from any multi range ADC and so
should be done with IIO_INFO_SCALE.

Sorry for taking so long to get back to you. Holiday season I'm afraid.

Jonathan
> ---
> MAINTAINERS | 4 +-
> drivers/iio/adc/Kconfig | 15 ++++
> drivers/iio/adc/Makefile | 1 +
> drivers/iio/{dac => adc}/stx104.c | 157 ++++++++++++++++++++++++++++++++------
> drivers/iio/dac/Kconfig | 10 ---
> drivers/iio/dac/Makefile | 1 -
> 6 files changed, 151 insertions(+), 37 deletions(-)
> rename drivers/iio/{dac => adc}/stx104.c (59%)
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index b5c802d..cda799c 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -792,11 +792,11 @@ L: alsa-devel@xxxxxxxxxxxxxxxx (moderated for non-subscribers)
> S: Maintained
> F: sound/aoa/
>
> -APEX EMBEDDED SYSTEMS STX104 DAC DRIVER
> +APEX EMBEDDED SYSTEMS STX104 IIO DRIVER
> M: William Breathitt Gray <vilhelm.gray@xxxxxxxxx>
> L: linux-iio@xxxxxxxxxxxxxxx
> S: Maintained
> -F: drivers/iio/dac/stx104.c
> +F: drivers/iio/adc/stx104.c
>
> APM DRIVER
> M: Jiri Kosina <jikos@xxxxxxxxxx>
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 1de31bd..ec9ada8 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -396,6 +396,21 @@ config ROCKCHIP_SARADC
> To compile this driver as a module, choose M here: the
> module will be called rockchip_saradc.
>
> +config STX104
> + tristate "Apex Embedded Systems STX104 driver"
> + depends on X86 && ISA_BUS_API
> + select GPIOLIB
> + help
> + Say yes here to build support for the Apex Embedded Systems STX104
> + integrated analog PC/104 card.
> +
> + This driver supports the 16 channels of single-ended (8 channels of
> + differential) analog inputs, 2 channels of analog output, 4 digital
> + inputs, and 4 digital outputs provided by the STX104.
> +
> + The base port addresses for the devices may be configured via the base
> + array module parameter.
> +
> config TI_ADC081C
> tristate "Texas Instruments ADC081C/ADC101C/ADC121C family"
> depends on I2C
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index 0ba0d50..d7b4a71 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -38,6 +38,7 @@ obj-$(CONFIG_PALMAS_GPADC) += palmas_gpadc.o
> obj-$(CONFIG_QCOM_SPMI_IADC) += qcom-spmi-iadc.o
> obj-$(CONFIG_QCOM_SPMI_VADC) += qcom-spmi-vadc.o
> obj-$(CONFIG_ROCKCHIP_SARADC) += rockchip_saradc.o
> +obj-$(CONFIG_STX104) += stx104.o
> obj-$(CONFIG_TI_ADC081C) += ti-adc081c.o
> obj-$(CONFIG_TI_ADC0832) += ti-adc0832.o
> obj-$(CONFIG_TI_ADC128S052) += ti-adc128s052.o
> diff --git a/drivers/iio/dac/stx104.c b/drivers/iio/adc/stx104.c
> similarity index 59%
> rename from drivers/iio/dac/stx104.c
> rename to drivers/iio/adc/stx104.c
> index 792a971..8562766 100644
> --- a/drivers/iio/dac/stx104.c
> +++ b/drivers/iio/adc/stx104.c
> @@ -1,5 +1,5 @@
> /*
> - * DAC driver for the Apex Embedded Systems STX104
> + * IIO driver for the Apex Embedded Systems STX104
> * Copyright (C) 2016 William Breathitt Gray
> *
> * This program is free software; you can redistribute it and/or modify
> @@ -20,19 +20,29 @@
> #include <linux/io.h>
> #include <linux/ioport.h>
> #include <linux/isa.h>
> +#include <linux/kernel.h>
> #include <linux/module.h>
> #include <linux/moduleparam.h>
> #include <linux/spinlock.h>
>
> -#define STX104_NUM_CHAN 2
> -
> -#define STX104_CHAN(chan) { \
> +#define STX104_IO_CHAN(chan, dir, diff) { \
> .type = IIO_VOLTAGE, \
> .channel = chan, \
> + .channel2 = chan, \
> .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> .indexed = 1, \
> - .output = 1 \
> + .output = dir, \
> + .differential = diff \
> +}
> +#define STX104_GAIN_CHAN { \
> + .type = IIO_VOLTAGE, \
> + .info_mask_separate = BIT(IIO_CHAN_INFO_HARDWAREGAIN), \
> + .output = 1 \
> }

I'm confused. You have a separate output channel to control gain?
Why... Variable gain devices are normally just represented via the
info_mask element IIO_CHAN_INFO_SCALE as an info_mask_shared_by_type.

> +#define STX104_OUT_CHAN(chan) STX104_IO_CHAN(chan, 1, 0)
> +#define STX104_IN_CHAN(chan, diff) STX104_IO_CHAN(chan, 0, diff)
> +
> +#define STX104_NUM_OUT_CHAN 2
>
> #define STX104_EXTENT 16
>
> @@ -47,8 +57,8 @@ MODULE_PARM_DESC(base, "Apex Embedded Systems STX104 base addresses");
> * @base: base port address of the IIO device
> */
> struct stx104_iio {
> - unsigned chan_out_states[STX104_NUM_CHAN];
> - unsigned base;
> + unsigned int chan_out_states[STX104_NUM_OUT_CHAN];
> + unsigned int base;
> };
>
> /**
> @@ -69,39 +79,124 @@ static int stx104_read_raw(struct iio_dev *indio_dev,
> struct iio_chan_spec const *chan, int *val, int *val2, long mask)
> {
> struct stx104_iio *const priv = iio_priv(indio_dev);
> + long adc_sample;
> + unsigned int adc_config;
> + long adbu;
> + unsigned int gain;
> +
> + /* handle output channels */
> + if (chan->output) {
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
> + *val = priv->chan_out_states[chan->channel];
> + return IIO_VAL_INT;
> + case IIO_CHAN_INFO_HARDWAREGAIN:
> + *val = 1 << (inb(priv->base + 11) & 0x3);
> + return IIO_VAL_INT;
> + default:
> + return -EINVAL;
> + }
> + }
>
> if (mask != IIO_CHAN_INFO_RAW)
> return -EINVAL;
>
> - *val = priv->chan_out_states[chan->channel];
> -
> - return IIO_VAL_INT;
> + /* select ADC channel */
> + outb(chan->channel | (chan->channel << 4), priv->base + 2);
> +
> + /* trigger ADC sample capture and wait for completion */
> + outb(0, priv->base);
> + while (inb(priv->base + 8) & BIT(7));
> +
> + adc_sample = inw(priv->base);
> +
> + /* get ADC bipolar/unipolar and gain configuration */
> + adc_config = inb(priv->base + 11);
> + adbu = !(adc_config & BIT(2));
> + gain = adc_config & 0x3;
> +
> + /*
> + * Value conversion math:
> + * ----------------------
> + * scale = adc_sample / 65536
> + * range = 10 / (1 << gain)
> + * voltage = scale * (range + adbu * range) - adbu * range
> + *
> + * Simplified:
> + * -----------
> + * voltage = 5 * (adc_sample * (1 + adbu) - adbu * 65536) /
> + * (1 << (15 + gain))
> + */
> + *val = 5 * (adc_sample * (1 + adbu) - adbu * 65536);
> + *val2 = 15 + gain;
> +
> + return IIO_VAL_FRACTIONAL_LOG2;
> }
>
> static int stx104_write_raw(struct iio_dev *indio_dev,
> struct iio_chan_spec const *chan, int val, int val2, long mask)
> {
> struct stx104_iio *const priv = iio_priv(indio_dev);
> - const unsigned chan_addr_offset = 2 * chan->channel;
> -
> - if (mask != IIO_CHAN_INFO_RAW)
> - return -EINVAL;
>
> - priv->chan_out_states[chan->channel] = val;
> - outw(val, priv->base + 4 + chan_addr_offset);
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
> + /* DAC can only accept up to a 16-bit value */
> + if ((unsigned int)val > 65535)
> + return -EINVAL;
> +
> + priv->chan_out_states[chan->channel] = val;
> + outw(val, priv->base + 4 + 2 * chan->channel);
> +
> + return 0;
> + case IIO_CHAN_INFO_HARDWAREGAIN:
> + /* Only four gain states (x1, x2, x4, x8) */
> + switch (val) {
> + case 1:
> + outb(0, priv->base + 11);
> + break;
> + case 2:
> + outb(1, priv->base + 11);
> + break;
> + case 4:
> + outb(2, priv->base + 11);
> + break;
> + case 8:
> + outb(3, priv->base + 11);
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + return 0;
> + }
>
> - return 0;
> + return -EINVAL;
> }
>
> static const struct iio_info stx104_info = {
> .driver_module = THIS_MODULE,
> .read_raw = stx104_read_raw,
> - .write_raw = stx104_write_raw
> + .write_raw = stx104_write_raw,
> };
>
> -static const struct iio_chan_spec stx104_channels[STX104_NUM_CHAN] = {
> - STX104_CHAN(0),
> - STX104_CHAN(1)
> +/* single-ended input channels configuration */
> +static const struct iio_chan_spec stx104_channels_sing[] = {
> + STX104_OUT_CHAN(0), STX104_OUT_CHAN(1),
> + STX104_GAIN_CHAN,
> + STX104_IN_CHAN(0, 0), STX104_IN_CHAN(1, 0), STX104_IN_CHAN(2, 0),
> + STX104_IN_CHAN(3, 0), STX104_IN_CHAN(4, 0), STX104_IN_CHAN(5, 0),
> + STX104_IN_CHAN(6, 0), STX104_IN_CHAN(7, 0), STX104_IN_CHAN(8, 0),
> + STX104_IN_CHAN(9, 0), STX104_IN_CHAN(10, 0), STX104_IN_CHAN(11, 0),
> + STX104_IN_CHAN(12, 0), STX104_IN_CHAN(13, 0), STX104_IN_CHAN(14, 0),
> + STX104_IN_CHAN(15, 0)
> +};
> +/* differential input channels configuration */
> +static const struct iio_chan_spec stx104_channels_diff[] = {
> + STX104_OUT_CHAN(0), STX104_OUT_CHAN(1),
> + STX104_GAIN_CHAN,
> + STX104_IN_CHAN(0, 1), STX104_IN_CHAN(1, 1), STX104_IN_CHAN(2, 1),
> + STX104_IN_CHAN(3, 1), STX104_IN_CHAN(4, 1), STX104_IN_CHAN(5, 1),
> + STX104_IN_CHAN(6, 1), STX104_IN_CHAN(7, 1)
> };
>
> static int stx104_gpio_get_direction(struct gpio_chip *chip,
> @@ -188,13 +283,27 @@ static int stx104_probe(struct device *dev, unsigned int id)
>
> indio_dev->info = &stx104_info;
> indio_dev->modes = INDIO_DIRECT_MODE;
> - indio_dev->channels = stx104_channels;
> - indio_dev->num_channels = STX104_NUM_CHAN;
> +
> + /* determine if differential inputs */
> + if (inb(base[id] + 8) & BIT(5)) {
> + indio_dev->num_channels = ARRAY_SIZE(stx104_channels_diff);
> + indio_dev->channels = stx104_channels_diff;
> + } else {
> + indio_dev->num_channels = ARRAY_SIZE(stx104_channels_sing);
> + indio_dev->channels = stx104_channels_sing;
> + }
> +
> indio_dev->name = dev_name(dev);
>
> priv = iio_priv(indio_dev);
> priv->base = base[id];
>
> + /* configure device for software trigger operation */
> + outb(0, base[id] + 9);
> +
> + /* initialize gain setting to x1 */
> + outb(0, base[id] + 11);
> +
> /* initialize DAC output to 0V */
> outw(0, base[id] + 4);
> outw(0, base[id] + 6);
> @@ -251,5 +360,5 @@ static struct isa_driver stx104_driver = {
> module_isa_driver(stx104_driver, num_stx104);
>
> MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@xxxxxxxxx>");
> -MODULE_DESCRIPTION("Apex Embedded Systems STX104 DAC driver");
> +MODULE_DESCRIPTION("Apex Embedded Systems STX104 IIO driver");
> MODULE_LICENSE("GPL v2");
> diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
> index b9f0442..6048aed 100644
> --- a/drivers/iio/dac/Kconfig
> +++ b/drivers/iio/dac/Kconfig
> @@ -254,16 +254,6 @@ config MCP4922
> To compile this driver as a module, choose M here: the module
> will be called mcp4922.
>
> -config STX104
> - tristate "Apex Embedded Systems STX104 DAC driver"
> - depends on X86 && ISA_BUS_API
> - select GPIOLIB
> - help
> - Say yes here to build support for the 2-channel DAC and GPIO on the
> - Apex Embedded Systems STX104 integrated analog PC/104 card. The base
> - port addresses for the devices may be configured via the base array
> - module parameter.
> -
> config VF610_DAC
> tristate "Vybrid vf610 DAC driver"
> depends on OF
> diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
> index b1a1206..e6abef9 100644
> --- a/drivers/iio/dac/Makefile
> +++ b/drivers/iio/dac/Makefile
> @@ -27,5 +27,4 @@ obj-$(CONFIG_MAX517) += max517.o
> obj-$(CONFIG_MAX5821) += max5821.o
> obj-$(CONFIG_MCP4725) += mcp4725.o
> obj-$(CONFIG_MCP4922) += mcp4922.o
> -obj-$(CONFIG_STX104) += stx104.o
> obj-$(CONFIG_VF610_DAC) += vf610_dac.o
>

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