From b475f80b354a1915fda1b34070d712b825b60543 Mon Sep 17 00:00:00 2001 From: Peter Rosin Date: Tue, 8 Nov 2016 12:58:58 +0100 Subject: [PATCH] iio: envelope-detector: ADC driver based on a DAC and a comparator 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 Acked-by: Thomas Gleixner Signed-off-by: Jonathan Cameron --- .../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 +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 +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 76c3124fd62f..0393f1f1bee7 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -6131,7 +6131,9 @@ IIO ENVELOPE DETECTOR M: Peter Rosin L: linux-iio@vger.kernel.org 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 diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig index 57ebb997072c..6bbee0b0dfff 100644 --- a/drivers/iio/adc/Kconfig +++ b/drivers/iio/adc/Kconfig @@ -207,6 +207,16 @@ 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 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 96894b32300d..9391217648cb 100644 --- a/drivers/iio/adc/Makefile +++ b/drivers/iio/adc/Makefile @@ -21,6 +21,7 @@ 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 + * + * 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 +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +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 "); +MODULE_LICENSE("GPL v2"); -- 2.39.5