iio: stx104: Add IIO support for the ADC channels

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 <[email protected]>

---
 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%)

MAINTAINERS +2 -2

index b5c802d..cda799c 100644
@@ -792,11 +792,11 @@ L:	[email protected] (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 <[email protected]>
 L:	[email protected]
 S:	Maintained
-F:	drivers/iio/dac/stx104.c
+F:	drivers/iio/adc/stx104.c
 
 APM DRIVER
 M:	Jiri Kosina <[email protected]>

drivers/iio/adc/Kconfig +15 -0

index 1de31bd..ec9ada8 100644
@@ -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

drivers/iio/adc/Makefile +1 -0

index 0ba0d50..d7b4a71 100644
@@ -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

drivers/iio/adc/stx104.c renamed from drivers/iio/dac/stx104.c +4 -4

similarity index 59%
rename from drivers/iio/dac/stx104.c
rename to drivers/iio/adc/stx104.c
index 792a971..8562766 100644
@@ -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),	\

drivers/iio/adc/stx104.c renamed from drivers/iio/dac/stx104.c +122 -19

+#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 <[email protected]>");
-MODULE_DESCRIPTION("Apex Embedded Systems STX104 DAC driver");
+MODULE_DESCRIPTION("Apex Embedded Systems STX104 IIO driver");
 MODULE_LICENSE("GPL v2");

drivers/iio/dac/Kconfig +0 -10

index b9f0442..6048aed 100644
@@ -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

drivers/iio/dac/Makefile +0 -1

index b1a1206..e6abef9 100644
@@ -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

Quoted 15 lines · 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.

Quoted 7 lines

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 <[email protected]>

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

drivers/iio/adc/stx104.c line 41

Quoted 5 lines

drivers/iio/adc/stx104.c renamed from drivers/iio/dac/stx104.c +4 -0

+#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.

Quoted 35 lines · Jonathan Cameron

Quoted 15 lines · 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.

Quoted 7 lines

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 <[email protected]>

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

Quoted 9 lines

drivers/iio/adc/stx104.c line 41

Quoted 5 lines

drivers/iio/adc/stx104.c renamed from drivers/iio/dac/stx104.c +4 -0

+#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
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