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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-06 01:02:30 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-06 01:02:30 +0000 |
commit | 76cb841cb886eef6b3bee341a2266c76578724ad (patch) | |
tree | f5892e5ba6cc11949952a6ce4ecbe6d516d6ce58 /drivers/iio/adc/envelope-detector.c | |
parent | Initial commit. (diff) | |
download | linux-76cb841cb886eef6b3bee341a2266c76578724ad.tar.xz linux-76cb841cb886eef6b3bee341a2266c76578724ad.zip |
Adding upstream version 4.19.249.upstream/4.19.249upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'drivers/iio/adc/envelope-detector.c')
-rw-r--r-- | drivers/iio/adc/envelope-detector.c | 421 |
1 files changed, 421 insertions, 0 deletions
diff --git a/drivers/iio/adc/envelope-detector.c b/drivers/iio/adc/envelope-detector.c new file mode 100644 index 000000000..4ebda8ab5 --- /dev/null +++ b/drivers/iio/adc/envelope-detector.c @@ -0,0 +1,421 @@ +/* + * Driver for an envelope detector using a DAC and a comparator + * + * Copyright (C) 2016 Axentia Technologies AB + * + * Author: Peter Rosin <peda@axentia.se> + * + * 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, +}; + +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@axentia.se>"); +MODULE_LICENSE("GPL v2"); |