On 23/10/16 23:39, Peter Rosin wrote:
> The DAC is used to find the peak level of an alternating voltage input
> signal by a binary search using the output of a comparator wired to
> an interrupt pin. Like so:
> _
> | \
> input +------>-------|+ \
> | \
> .-------. | }---.
> | | | / |
> | dac|-->--|- / |
> | | |_/ |
> | | |
> | | |
> | irq|------<-------'
> | |
> '-------'
>
> Signed-off-by: Peter Rosin <peda@xxxxxxxxxx>
Looks good to me. I've cc'd Thomas Gleixner as the irq usage is obviously
a bit unusual and I thought he may have some thoughts on it.
Jonathan
> ---
> .../testing/sysfs-bus-iio-adc-envelope-detector | 36 ++
> MAINTAINERS | 2 +
> drivers/iio/adc/Kconfig | 10 +
> drivers/iio/adc/Makefile | 1 +
> drivers/iio/adc/envelope-detector.c | 422 +++++++++++++++++++++
> 5 files changed, 471 insertions(+)
> create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-adc-envelope-detector
> create mode 100644 drivers/iio/adc/envelope-detector.c
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-adc-envelope-detector b/Documentation/ABI/testing/sysfs-bus-iio-adc-envelope-detector
> new file mode 100644
> index 000000000000..2071f9bcfaa5
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-iio-adc-envelope-detector
> @@ -0,0 +1,36 @@
> +What: /sys/bus/iio/devices/iio:deviceX/in_altvoltageY_invert
> +Date: October 2016
> +KernelVersion: 4.9
> +Contact: Peter Rosin <peda@xxxxxxxxxx>
> +Description:
> + The DAC is used to find the peak level of an alternating
> + voltage input signal by a binary search using the output
> + of a comparator wired to an interrupt pin. Like so:
> + _
> + | \
> + input +------>-------|+ \
> + | \
> + .-------. | }---.
> + | | | / |
> + | dac|-->--|- / |
> + | | |_/ |
> + | | |
> + | | |
> + | irq|------<-------'
> + | |
> + '-------'
> + The boolean invert attribute (0/1) should be set when the
> + input signal is centered around the maximum value of the
> + dac instead of zero. The envelope detector will search
> + from below in this case and will also invert the result.
> + The edge/level of the interrupt is also switched to its
> + opposite value.
> +
> +What: /sys/bus/iio/devices/iio:deviceX/in_altvoltageY_compare_interval
> +Date: October 2016
> +KernelVersion: 4.9
> +Contact: Peter Rosin <peda@xxxxxxxxxx>
> +Description:
> + Number of milliseconds to wait for the comparator in each
> + step of the binary search for the input peak level. Needs
> + to relate to the frequency of the input signal.
> diff --git a/MAINTAINERS b/MAINTAINERS
> index fca35d16037d..0cf3549e05e7 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -6123,7 +6123,9 @@ IIO ENVELOPE DETECTOR
> M: Peter Rosin <peda@xxxxxxxxxx>
> L: linux-iio@xxxxxxxxxxxxxxx
> S: Maintained
> +F: Documentation/ABI/testing/sysfs-bus-iio-adc-envelope-detector
> F: Documentation/devicetree/bindings/iio/adc/envelope-detector.txt
> +F: drivers/iio/adc/envelope-detector.c
>
> IIO SUBSYSTEM AND DRIVERS
> M: Jonathan Cameron <jic23@xxxxxxxxxx>
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 7edcf3238620..d5c4a95855c2 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -195,6 +195,16 @@ config DA9150_GPADC
> To compile this driver as a module, choose M here: the module will be
> called berlin2-adc.
>
> +config ENVELOPE_DETECTOR
> + tristate "Envelope detector using a DAC and a comparator"
> + depends on OF
> + help
> + Say yes here to build support for an envelope detector using a DAC
> + and a comparator.
> +
> + To compile this driver as a module, choose M here: the module will be
> + called iio-envelope-detector.
> +
> config EXYNOS_ADC
> tristate "Exynos ADC driver support"
> depends on ARCH_EXYNOS || ARCH_S3C24XX || ARCH_S3C64XX || (OF && COMPILE_TEST)
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index 7a40c04c311f..0d773c6a0578 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -20,6 +20,7 @@ obj-$(CONFIG_BCM_IPROC_ADC) += bcm_iproc_adc.o
> obj-$(CONFIG_BERLIN2_ADC) += berlin2-adc.o
> obj-$(CONFIG_CC10001_ADC) += cc10001_adc.o
> obj-$(CONFIG_DA9150_GPADC) += da9150-gpadc.o
> +obj-$(CONFIG_ENVELOPE_DETECTOR) += envelope-detector.o
> obj-$(CONFIG_EXYNOS_ADC) += exynos_adc.o
> obj-$(CONFIG_FSL_MX25_ADC) += fsl-imx25-gcq.o
> obj-$(CONFIG_HI8435) += hi8435.o
> diff --git a/drivers/iio/adc/envelope-detector.c b/drivers/iio/adc/envelope-detector.c
> new file mode 100644
> index 000000000000..fef15c0d7c9c
> --- /dev/null
> +++ b/drivers/iio/adc/envelope-detector.c
> @@ -0,0 +1,422 @@
> +/*
> + * Driver for an envelope detector using a DAC and a comparator
> + *
> + * Copyright (C) 2016 Axentia Technologies AB
> + *
> + * Author: Peter Rosin <peda@xxxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +/*
> + * The DAC is used to find the peak level of an alternating voltage input
> + * signal by a binary search using the output of a comparator wired to
> + * an interrupt pin. Like so:
> + * _
> + * | \
> + * input +------>-------|+ \
> + * | \
> + * .-------. | }---.
> + * | | | / |
> + * | dac|-->--|- / |
> + * | | |_/ |
> + * | | |
> + * | | |
> + * | irq|------<-------'
> + * | |
> + * '-------'
> + */
> +
> +#include <linux/completion.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/iio/consumer.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/interrupt.h>
> +#include <linux/irq.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/spinlock.h>
> +#include <linux/workqueue.h>
> +
> +struct envelope {
> + spinlock_t comp_lock; /* protects comp */
> + int comp;
> +
> + struct mutex read_lock; /* protects everything else */
> +
> + int comp_irq;
> + u32 comp_irq_trigger;
> + u32 comp_irq_trigger_inv;
> +
> + struct iio_channel *dac;
> + struct delayed_work comp_timeout;
> +
> + unsigned int comp_interval;
> + bool invert;
> + u32 dac_max;
> +
> + int high;
> + int level;
> + int low;
> +
> + struct completion done;
> +};
> +
> +/*
> + * The envelope_detector_comp_latch function works together with the compare
> + * interrupt service routine below (envelope_detector_comp_isr) as a latch
> + * (one-bit memory) for if the interrupt has triggered since last calling
> + * this function.
> + * The ..._comp_isr function disables the interrupt so that the cpu does not
> + * need to service a possible interrupt flood from the comparator when no-one
> + * cares anyway, and this ..._comp_latch function reenables them again if
> + * needed.
> + */
> +static int envelope_detector_comp_latch(struct envelope *env)
> +{
> + int comp;
> +
> + spin_lock_irq(&env->comp_lock);
> + comp = env->comp;
> + env->comp = 0;
> + spin_unlock_irq(&env->comp_lock);
> +
> + if (!comp)
> + return 0;
> +
> + /*
> + * The irq was disabled, and is reenabled just now.
> + * But there might have been a pending irq that
> + * happened while the irq was disabled that fires
> + * just as the irq is reenabled. That is not what
> + * is desired.
> + */
> + enable_irq(env->comp_irq);
> +
> + /* So, synchronize this possibly pending irq... */
> + synchronize_irq(env->comp_irq);
> +
> + /* ...and redo the whole dance. */
> + spin_lock_irq(&env->comp_lock);
> + comp = env->comp;
> + env->comp = 0;
> + spin_unlock_irq(&env->comp_lock);
> +
> + if (comp)
> + enable_irq(env->comp_irq);
> +
> + return 1;
> +}
> +
> +static irqreturn_t envelope_detector_comp_isr(int irq, void *ctx)
> +{
> + struct envelope *env = ctx;
> +
> + spin_lock(&env->comp_lock);
> + env->comp = 1;
> + disable_irq_nosync(env->comp_irq);
> + spin_unlock(&env->comp_lock);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static void envelope_detector_setup_compare(struct envelope *env)
> +{
> + int ret;
> +
> + /*
> + * Do a binary search for the peak input level, and stop
> + * when that level is "trapped" between two adjacent DAC
> + * values.
> + * When invert is active, use the midpoint floor so that
> + * env->level ends up as env->low when the termination
> + * criteria below is fulfilled, and use the midpoint
> + * ceiling when invert is not active so that env->level
> + * ends up as env->high in that case.
> + */
> + env->level = (env->high + env->low + !env->invert) / 2;
> +
> + if (env->high == env->low + 1) {
> + complete(&env->done);
> + return;
> + }
> +
> + /* Set a "safe" DAC level (if there is such a thing)... */
> + ret = iio_write_channel_raw(env->dac, env->invert ? 0 : env->dac_max);
> + if (ret < 0)
> + goto err;
> +
> + /* ...clear the comparison result... */
> + envelope_detector_comp_latch(env);
> +
> + /* ...set the real DAC level... */
> + ret = iio_write_channel_raw(env->dac, env->level);
> + if (ret < 0)
> + goto err;
> +
> + /* ...and wait for a bit to see if the latch catches anything. */
> + schedule_delayed_work(&env->comp_timeout,
> + msecs_to_jiffies(env->comp_interval));
> + return;
> +
> +err:
> + env->level = ret;
> + complete(&env->done);
> +}
> +
> +static void envelope_detector_timeout(struct work_struct *work)
> +{
> + struct envelope *env = container_of(work, struct envelope,
> + comp_timeout.work);
> +
> + /* Adjust low/high depending on the latch content... */
> + if (!envelope_detector_comp_latch(env) ^ !env->invert)
> + env->low = env->level;
> + else
> + env->high = env->level;
> +
> + /* ...and continue the search. */
> + envelope_detector_setup_compare(env);
> +}
> +
> +static int envelope_detector_read_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int *val, int *val2, long mask)
> +{
> + struct envelope *env = iio_priv(indio_dev);
> + int ret;
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
> + /*
> + * When invert is active, start with high=max+1 and low=0
> + * since we will end up with the low value when the
> + * termination criteria is fulfilled (rounding down). And
> + * start with high=max and low=-1 when invert is not active
> + * since we will end up with the high value in that case.
> + * This ensures that the returned value in both cases are
> + * in the same range as the DAC and is a value that has not
> + * triggered the comparator.
> + */
> + mutex_lock(&env->read_lock);
> + env->high = env->dac_max + env->invert;
> + env->low = -1 + env->invert;
> + envelope_detector_setup_compare(env);
> + wait_for_completion(&env->done);
> + if (env->level < 0) {
> + ret = env->level;
> + goto err_unlock;
> + }
> + *val = env->invert ? env->dac_max - env->level : env->level;
> + mutex_unlock(&env->read_lock);
> +
> + return IIO_VAL_INT;
> +
> + case IIO_CHAN_INFO_SCALE:
> + return iio_read_channel_scale(env->dac, val, val2);
> + }
> +
> + return -EINVAL;
> +
> +err_unlock:
> + mutex_unlock(&env->read_lock);
> + return ret;
> +}
> +
> +static ssize_t envelope_show_invert(struct iio_dev *indio_dev,
> + uintptr_t private,
> + struct iio_chan_spec const *ch, char *buf)
> +{
> + struct envelope *env = iio_priv(indio_dev);
> +
> + return sprintf(buf, "%u\n", env->invert);
> +}
> +
> +static ssize_t envelope_store_invert(struct iio_dev *indio_dev,
> + uintptr_t private,
> + struct iio_chan_spec const *ch,
> + const char *buf, size_t len)
> +{
> + struct envelope *env = iio_priv(indio_dev);
> + unsigned long invert;
> + int ret;
> + u32 trigger;
> +
> + ret = kstrtoul(buf, 0, &invert);
> + if (ret < 0)
> + return ret;
> + if (invert > 1)
> + return -EINVAL;
> +
> + trigger = invert ? env->comp_irq_trigger_inv : env->comp_irq_trigger;
> +
> + mutex_lock(&env->read_lock);
> + if (invert != env->invert)
> + ret = irq_set_irq_type(env->comp_irq, trigger);
> + if (!ret) {
> + env->invert = invert;
> + ret = len;
> + }
> + mutex_unlock(&env->read_lock);
> +
> + return ret;
> +}
> +
> +static ssize_t envelope_show_comp_interval(struct iio_dev *indio_dev,
> + uintptr_t private,
> + struct iio_chan_spec const *ch,
> + char *buf)
> +{
> + struct envelope *env = iio_priv(indio_dev);
> +
> + return sprintf(buf, "%u\n", env->comp_interval);
> +}
> +
> +static ssize_t envelope_store_comp_interval(struct iio_dev *indio_dev,
> + uintptr_t private,
> + struct iio_chan_spec const *ch,
> + const char *buf, size_t len)
> +{
> + struct envelope *env = iio_priv(indio_dev);
> + unsigned long interval;
> + int ret;
> +
> + ret = kstrtoul(buf, 0, &interval);
> + if (ret < 0)
> + return ret;
> + if (interval > 1000)
> + return -EINVAL;
> +
> + mutex_lock(&env->read_lock);
> + env->comp_interval = interval;
> + mutex_unlock(&env->read_lock);
> +
> + return len;
> +}
> +
> +static const struct iio_chan_spec_ext_info envelope_detector_ext_info[] = {
> + { .name = "invert",
> + .read = envelope_show_invert,
> + .write = envelope_store_invert, },
> + { .name = "compare_interval",
> + .read = envelope_show_comp_interval,
> + .write = envelope_store_comp_interval, },
> + { /* sentinel */ }
> +};
> +
> +static const struct iio_chan_spec envelope_detector_iio_channel = {
> + .type = IIO_ALTVOLTAGE,
> + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW)
> + | BIT(IIO_CHAN_INFO_SCALE),
> + .ext_info = envelope_detector_ext_info,
> + .indexed = 1,
> +};
> +
> +static const struct iio_info envelope_detector_info = {
> + .read_raw = &envelope_detector_read_raw,
> + .driver_module = THIS_MODULE,
> +};
> +
> +static int envelope_detector_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct iio_dev *indio_dev;
> + struct envelope *env;
> + enum iio_chan_type type;
> + int ret;
> +
> + indio_dev = devm_iio_device_alloc(dev, sizeof(*env));
> + if (!indio_dev)
> + return -ENOMEM;
> +
> + platform_set_drvdata(pdev, indio_dev);
> + env = iio_priv(indio_dev);
> + env->comp_interval = 50; /* some sensible default? */
> +
> + spin_lock_init(&env->comp_lock);
> + mutex_init(&env->read_lock);
> + init_completion(&env->done);
> + INIT_DELAYED_WORK(&env->comp_timeout, envelope_detector_timeout);
> +
> + indio_dev->name = dev_name(dev);
> + indio_dev->dev.parent = dev;
> + indio_dev->dev.of_node = dev->of_node;
> + indio_dev->info = &envelope_detector_info;
> + indio_dev->channels = &envelope_detector_iio_channel;
> + indio_dev->num_channels = 1;
> +
> + env->dac = devm_iio_channel_get(dev, "dac");
> + if (IS_ERR(env->dac)) {
> + if (PTR_ERR(env->dac) != -EPROBE_DEFER)
> + dev_err(dev, "failed to get dac input channel\n");
> + return PTR_ERR(env->dac);
> + }
> +
> + env->comp_irq = platform_get_irq_byname(pdev, "comp");
> + if (env->comp_irq < 0) {
> + if (env->comp_irq != -EPROBE_DEFER)
> + dev_err(dev, "failed to get compare interrupt\n");
> + return env->comp_irq;
> + }
> +
> + ret = devm_request_irq(dev, env->comp_irq, envelope_detector_comp_isr,
> + 0, "envelope-detector", env);
> + if (ret) {
> + if (ret != -EPROBE_DEFER)
> + dev_err(dev, "failed to request interrupt\n");
> + return ret;
> + }
> + env->comp_irq_trigger = irq_get_trigger_type(env->comp_irq);
> + if (env->comp_irq_trigger & IRQF_TRIGGER_RISING)
> + env->comp_irq_trigger_inv |= IRQF_TRIGGER_FALLING;
> + if (env->comp_irq_trigger & IRQF_TRIGGER_FALLING)
> + env->comp_irq_trigger_inv |= IRQF_TRIGGER_RISING;
> + if (env->comp_irq_trigger & IRQF_TRIGGER_HIGH)
> + env->comp_irq_trigger_inv |= IRQF_TRIGGER_LOW;
> + if (env->comp_irq_trigger & IRQF_TRIGGER_LOW)
> + env->comp_irq_trigger_inv |= IRQF_TRIGGER_HIGH;
> +
> + ret = iio_get_channel_type(env->dac, &type);
> + if (ret < 0)
> + return ret;
> +
> + if (type != IIO_VOLTAGE) {
> + dev_err(dev, "dac is of the wrong type\n");
> + return -EINVAL;
> + }
> +
> + ret = iio_read_max_channel_raw(env->dac, &env->dac_max);
> + if (ret < 0) {
> + dev_err(dev, "dac does not indicate its raw maximum value\n");
> + return ret;
> + }
> +
> + return devm_iio_device_register(dev, indio_dev);
> +}
> +
> +static const struct of_device_id envelope_detector_match[] = {
> + { .compatible = "axentia,tse850-envelope-detector", },
> + { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, envelope_detector_match);
> +
> +static struct platform_driver envelope_detector_driver = {
> + .probe = envelope_detector_probe,
> + .driver = {
> + .name = "iio-envelope-detector",
> + .of_match_table = envelope_detector_match,
> + },
> +};
> +module_platform_driver(envelope_detector_driver);
> +
> +MODULE_DESCRIPTION("Envelope detector using a DAC and a comparator");
> +MODULE_AUTHOR("Peter Rosin <peda@xxxxxxxxxx>");
> +MODULE_LICENSE("GPL v2");
>
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