[PATCH v4 0/1] iio: stx104: Add IIO support for the ADC channels

[PATCH v4 0/1] iio: stx104: Add IIO support for the ADC channels

[William Breathitt Gray]

Changes in v4:
  - Replace "DAC" with "IIO" in the MAINTAINERS file entry for the STX104 since
    this driver now supports the ADC functionality rather than simply the DAC
Changes in v3:
  - Squash move patch as unneeded thanks to "git format-patch -M"
  - Fix multiline comment syntax for value conversion math explanation
  - Select between two const iio_chan_spec structures in order to support
    differential input channels configuration correctly for multiple devices
Changes in v2:
  - IIO_CHAN_INFO_RAW mask used for analog input channels
  - STX104_ prefix added to IN_CHAN_OFFSET define
  - STX104_MAX_NUM_CHAN define removed as unnecessary
  - Whitespace added to pad comment about ADC sample capture and completion wait
  - Switch statement in write_raw callback refactored to return 0
  - Comma added to last element initialization of stx104_info
  - Comment added to warn why stx104_channels is not const
  - Comment added to explain GPIO offset in gpio_get_direction callback
  - ARRAY_SIZE macro utilized to get number of channels in stx104_channels
  - Replace devm_iio_device_register with iio_device_register call and
    respective iio_device_unregister call
  - Perform GPIO chip registration before iio_device_register to prevent race
    condition

The first patch of version 2 of this patchset ("iio: stx104: Unregister IIO
device on remove callback") has been removed from this patchset since it was
picked up in the iio.git fixes-togreg-post-rc1 branch.

The move patch of version 2 of this patchset has been squashed with the ADC
support implementation code since the "git format-patch -M" command has been
used to clarify the rename of the stx104.c file from the dac directory to the
adc directory.

William Breathitt Gray (1):
  iio: stx104: Add IIO support for the ADC channels

 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%)

-- 
2.7.3

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

[William Breathitt Gray]

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@gmail.com>
---
 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@alsa-project.org (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@gmail.com>
 L:	linux-iio@vger.kernel.org
 S:	Maintained
-F:	drivers/iio/dac/stx104.c
+F:	drivers/iio/adc/stx104.c
 
 APM DRIVER
 M:	Jiri Kosina <jikos@kernel.org>
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						\
 }
+#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@gmail.com>");
-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
-- 
2.7.3

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

[Jonathan Cameron]

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@gmail.com>
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@alsa-project.org (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@gmail.com>
>  L:	linux-iio@vger.kernel.org
>  S:	Maintained
> -F:	drivers/iio/dac/stx104.c
> +F:	drivers/iio/adc/stx104.c
>  
>  APM DRIVER
>  M:	Jiri Kosina <jikos@kernel.org>
> 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@gmail.com>");
> -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
> 

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

[William Breathitt Gray]

On Sun, Aug 21, 2016 at 08:39:01PM +0100, Jonathan Cameron wrote:
>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@gmail.com>
>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

>> +#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.

Hey Jonathan,

Thanks for getting back to me. I did have trouble figuring out the
proper way to expose the gain control for this device. Perhaps if I
describe the register interface it may make more sense.

The STX104 ADC input range may be probed with a read to register offset
11; bit 2 represents the ADC bipolar/unipolar configuration (ADBU),
while bits 1 and 0 represent the ADC gain setting. ADBU is configured by
physical jumper on the device, while the ADC gain setting is configured
in software via a register write.

ADC gain may be set with a write of bits 1 and 0 to register offset 11;
00 = gain of x1, 01 = gain of x2, 10 = gain of x4, 11 = gain of x8.
Writing to this register sets the analog input gain for all 8/16 analog
inputs.

Since the ADC gain setting applies to all analog inputs rather than
individual inputs separately, what is the proper way to expose this
option? Should I remove the STX104_GAIN_CHAN #define entirely and use
something like the following change instead:

	#define STX104_IN_CHAN(chan, diff) {				\
		.type = IIO_VOLTAGE,					\
		.channel = chan,					\
		.channel2 = chan,					\
		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
		.indexed = 1,						\
		.output = 0,						\
		.differential = diff					\
	}

Where the IIO_CHAN_INFO_SCALE now exposes the gain setting affecting all
analog inputs.

Thanks,

William Breathitt Gray

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

[Jonathan Cameron]

On 22/08/16 14:24, William Breathitt Gray wrote:
> On Sun, Aug 21, 2016 at 08:39:01PM +0100, Jonathan Cameron wrote:
>> 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@gmail.com>
>> 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
> 
>>> +#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.
> 
> Hey Jonathan,
> 
> Thanks for getting back to me. I did have trouble figuring out the
> proper way to expose the gain control for this device. Perhaps if I
> describe the register interface it may make more sense.
> 
> The STX104 ADC input range may be probed with a read to register offset
> 11; bit 2 represents the ADC bipolar/unipolar configuration (ADBU),
> while bits 1 and 0 represent the ADC gain setting. ADBU is configured by
> physical jumper on the device, while the ADC gain setting is configured
> in software via a register write.
> 
> ADC gain may be set with a write of bits 1 and 0 to register offset 11;
> 00 = gain of x1, 01 = gain of x2, 10 = gain of x4, 11 = gain of x8.
> Writing to this register sets the analog input gain for all 8/16 analog
> inputs.
> 
> Since the ADC gain setting applies to all analog inputs rather than
> individual inputs separately, what is the proper way to expose this
> option? Should I remove the STX104_GAIN_CHAN #define entirely and use
> something like the following change instead:
> 
> 	#define STX104_IN_CHAN(chan, diff) {				\
> 		.type = IIO_VOLTAGE,					\
> 		.channel = chan,					\
> 		.channel2 = chan,					\
> 		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
> 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
> 		.indexed = 1,						\
> 		.output = 0,						\
> 		.differential = diff					\
> 	}
> 
> Where the IIO_CHAN_INFO_SCALE now exposes the gain setting affecting all
> analog inputs.
Yes.  Basically using shared_by_type gives it an appropriate name
in_voltage_scale and though you have the entry every time, only one attribute
is created.  The others act more as documentation in the code than anything
else (so they should be there).

Jonathan
> 
> Thanks,
> 
> William Breathitt Gray
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