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409 lines
11 KiB
409 lines
11 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Driver for an envelope detector using a DAC and a comparator |
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* |
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* Copyright (C) 2016 Axentia Technologies AB |
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* |
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* Author: Peter Rosin <[email protected]> |
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*/ |
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|
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/* |
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* The DAC is used to find the peak level of an alternating voltage input |
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* signal by a binary search using the output of a comparator wired to |
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* an interrupt pin. Like so: |
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* _ |
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* | \ |
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* input +------>-------|+ \ |
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* | \ |
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* .-------. | }---. |
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* | | | / | |
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* | dac|-->--|- / | |
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* | | |_/ | |
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* | | | |
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* | | | |
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* | irq|------<-------' |
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* | | |
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* '-------' |
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*/ |
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#include <linux/completion.h> |
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#include <linux/device.h> |
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#include <linux/err.h> |
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#include <linux/kernel.h> |
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#include <linux/module.h> |
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#include <linux/mutex.h> |
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#include <linux/iio/consumer.h> |
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#include <linux/iio/iio.h> |
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#include <linux/iio/sysfs.h> |
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#include <linux/interrupt.h> |
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#include <linux/irq.h> |
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#include <linux/of.h> |
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#include <linux/of_device.h> |
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#include <linux/platform_device.h> |
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#include <linux/spinlock.h> |
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#include <linux/workqueue.h> |
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struct envelope { |
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spinlock_t comp_lock; /* protects comp */ |
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int comp; |
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struct mutex read_lock; /* protects everything else */ |
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int comp_irq; |
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u32 comp_irq_trigger; |
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u32 comp_irq_trigger_inv; |
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struct iio_channel *dac; |
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struct delayed_work comp_timeout; |
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unsigned int comp_interval; |
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bool invert; |
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u32 dac_max; |
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int high; |
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int level; |
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int low; |
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struct completion done; |
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}; |
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/* |
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* The envelope_detector_comp_latch function works together with the compare |
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* interrupt service routine below (envelope_detector_comp_isr) as a latch |
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* (one-bit memory) for if the interrupt has triggered since last calling |
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* this function. |
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* The ..._comp_isr function disables the interrupt so that the cpu does not |
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* need to service a possible interrupt flood from the comparator when no-one |
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* cares anyway, and this ..._comp_latch function reenables them again if |
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* needed. |
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*/ |
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static int envelope_detector_comp_latch(struct envelope *env) |
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{ |
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int comp; |
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spin_lock_irq(&env->comp_lock); |
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comp = env->comp; |
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env->comp = 0; |
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spin_unlock_irq(&env->comp_lock); |
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if (!comp) |
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return 0; |
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/* |
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* The irq was disabled, and is reenabled just now. |
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* But there might have been a pending irq that |
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* happened while the irq was disabled that fires |
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* just as the irq is reenabled. That is not what |
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* is desired. |
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*/ |
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enable_irq(env->comp_irq); |
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/* So, synchronize this possibly pending irq... */ |
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synchronize_irq(env->comp_irq); |
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/* ...and redo the whole dance. */ |
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spin_lock_irq(&env->comp_lock); |
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comp = env->comp; |
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env->comp = 0; |
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spin_unlock_irq(&env->comp_lock); |
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if (comp) |
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enable_irq(env->comp_irq); |
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return 1; |
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} |
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static irqreturn_t envelope_detector_comp_isr(int irq, void *ctx) |
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{ |
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struct envelope *env = ctx; |
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spin_lock(&env->comp_lock); |
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env->comp = 1; |
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disable_irq_nosync(env->comp_irq); |
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spin_unlock(&env->comp_lock); |
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return IRQ_HANDLED; |
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} |
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static void envelope_detector_setup_compare(struct envelope *env) |
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{ |
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int ret; |
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/* |
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* Do a binary search for the peak input level, and stop |
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* when that level is "trapped" between two adjacent DAC |
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* values. |
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* When invert is active, use the midpoint floor so that |
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* env->level ends up as env->low when the termination |
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* criteria below is fulfilled, and use the midpoint |
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* ceiling when invert is not active so that env->level |
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* ends up as env->high in that case. |
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*/ |
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env->level = (env->high + env->low + !env->invert) / 2; |
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if (env->high == env->low + 1) { |
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complete(&env->done); |
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return; |
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} |
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/* Set a "safe" DAC level (if there is such a thing)... */ |
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ret = iio_write_channel_raw(env->dac, env->invert ? 0 : env->dac_max); |
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if (ret < 0) |
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goto err; |
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/* ...clear the comparison result... */ |
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envelope_detector_comp_latch(env); |
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/* ...set the real DAC level... */ |
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ret = iio_write_channel_raw(env->dac, env->level); |
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if (ret < 0) |
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goto err; |
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/* ...and wait for a bit to see if the latch catches anything. */ |
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schedule_delayed_work(&env->comp_timeout, |
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msecs_to_jiffies(env->comp_interval)); |
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return; |
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err: |
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env->level = ret; |
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complete(&env->done); |
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} |
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static void envelope_detector_timeout(struct work_struct *work) |
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{ |
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struct envelope *env = container_of(work, struct envelope, |
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comp_timeout.work); |
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/* Adjust low/high depending on the latch content... */ |
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if (!envelope_detector_comp_latch(env) ^ !env->invert) |
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env->low = env->level; |
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else |
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env->high = env->level; |
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/* ...and continue the search. */ |
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envelope_detector_setup_compare(env); |
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} |
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static int envelope_detector_read_raw(struct iio_dev *indio_dev, |
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struct iio_chan_spec const *chan, |
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int *val, int *val2, long mask) |
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{ |
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struct envelope *env = iio_priv(indio_dev); |
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int ret; |
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switch (mask) { |
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case IIO_CHAN_INFO_RAW: |
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/* |
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* When invert is active, start with high=max+1 and low=0 |
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* since we will end up with the low value when the |
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* termination criteria is fulfilled (rounding down). And |
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* start with high=max and low=-1 when invert is not active |
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* since we will end up with the high value in that case. |
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* This ensures that the returned value in both cases are |
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* in the same range as the DAC and is a value that has not |
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* triggered the comparator. |
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*/ |
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mutex_lock(&env->read_lock); |
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env->high = env->dac_max + env->invert; |
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env->low = -1 + env->invert; |
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envelope_detector_setup_compare(env); |
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wait_for_completion(&env->done); |
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if (env->level < 0) { |
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ret = env->level; |
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goto err_unlock; |
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} |
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*val = env->invert ? env->dac_max - env->level : env->level; |
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mutex_unlock(&env->read_lock); |
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return IIO_VAL_INT; |
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case IIO_CHAN_INFO_SCALE: |
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return iio_read_channel_scale(env->dac, val, val2); |
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} |
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return -EINVAL; |
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err_unlock: |
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mutex_unlock(&env->read_lock); |
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return ret; |
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} |
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static ssize_t envelope_show_invert(struct iio_dev *indio_dev, |
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uintptr_t private, |
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struct iio_chan_spec const *ch, char *buf) |
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{ |
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struct envelope *env = iio_priv(indio_dev); |
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return sprintf(buf, "%u\n", env->invert); |
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} |
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static ssize_t envelope_store_invert(struct iio_dev *indio_dev, |
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uintptr_t private, |
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struct iio_chan_spec const *ch, |
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const char *buf, size_t len) |
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{ |
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struct envelope *env = iio_priv(indio_dev); |
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unsigned long invert; |
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int ret; |
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u32 trigger; |
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ret = kstrtoul(buf, 0, &invert); |
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if (ret < 0) |
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return ret; |
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if (invert > 1) |
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return -EINVAL; |
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trigger = invert ? env->comp_irq_trigger_inv : env->comp_irq_trigger; |
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mutex_lock(&env->read_lock); |
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if (invert != env->invert) |
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ret = irq_set_irq_type(env->comp_irq, trigger); |
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if (!ret) { |
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env->invert = invert; |
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ret = len; |
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} |
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mutex_unlock(&env->read_lock); |
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return ret; |
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} |
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static ssize_t envelope_show_comp_interval(struct iio_dev *indio_dev, |
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uintptr_t private, |
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struct iio_chan_spec const *ch, |
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char *buf) |
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{ |
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struct envelope *env = iio_priv(indio_dev); |
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return sprintf(buf, "%u\n", env->comp_interval); |
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} |
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static ssize_t envelope_store_comp_interval(struct iio_dev *indio_dev, |
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uintptr_t private, |
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struct iio_chan_spec const *ch, |
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const char *buf, size_t len) |
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{ |
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struct envelope *env = iio_priv(indio_dev); |
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unsigned long interval; |
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int ret; |
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ret = kstrtoul(buf, 0, &interval); |
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if (ret < 0) |
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return ret; |
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if (interval > 1000) |
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return -EINVAL; |
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mutex_lock(&env->read_lock); |
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env->comp_interval = interval; |
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mutex_unlock(&env->read_lock); |
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return len; |
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} |
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static const struct iio_chan_spec_ext_info envelope_detector_ext_info[] = { |
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{ .name = "invert", |
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.read = envelope_show_invert, |
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.write = envelope_store_invert, }, |
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{ .name = "compare_interval", |
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.read = envelope_show_comp_interval, |
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.write = envelope_store_comp_interval, }, |
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{ /* sentinel */ } |
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}; |
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static const struct iio_chan_spec envelope_detector_iio_channel = { |
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.type = IIO_ALTVOLTAGE, |
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.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
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| BIT(IIO_CHAN_INFO_SCALE), |
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.ext_info = envelope_detector_ext_info, |
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.indexed = 1, |
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}; |
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static const struct iio_info envelope_detector_info = { |
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.read_raw = &envelope_detector_read_raw, |
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}; |
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static int envelope_detector_probe(struct platform_device *pdev) |
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{ |
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struct device *dev = &pdev->dev; |
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struct iio_dev *indio_dev; |
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struct envelope *env; |
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enum iio_chan_type type; |
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int ret; |
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indio_dev = devm_iio_device_alloc(dev, sizeof(*env)); |
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if (!indio_dev) |
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return -ENOMEM; |
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platform_set_drvdata(pdev, indio_dev); |
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env = iio_priv(indio_dev); |
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env->comp_interval = 50; /* some sensible default? */ |
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spin_lock_init(&env->comp_lock); |
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mutex_init(&env->read_lock); |
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init_completion(&env->done); |
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INIT_DELAYED_WORK(&env->comp_timeout, envelope_detector_timeout); |
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indio_dev->name = dev_name(dev); |
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indio_dev->info = &envelope_detector_info; |
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indio_dev->channels = &envelope_detector_iio_channel; |
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indio_dev->num_channels = 1; |
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env->dac = devm_iio_channel_get(dev, "dac"); |
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if (IS_ERR(env->dac)) |
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return dev_err_probe(dev, PTR_ERR(env->dac), |
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"failed to get dac input channel\n"); |
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env->comp_irq = platform_get_irq_byname(pdev, "comp"); |
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if (env->comp_irq < 0) |
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return env->comp_irq; |
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ret = devm_request_irq(dev, env->comp_irq, envelope_detector_comp_isr, |
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0, "envelope-detector", env); |
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if (ret) |
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return dev_err_probe(dev, ret, "failed to request interrupt\n"); |
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env->comp_irq_trigger = irq_get_trigger_type(env->comp_irq); |
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if (env->comp_irq_trigger & IRQF_TRIGGER_RISING) |
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env->comp_irq_trigger_inv |= IRQF_TRIGGER_FALLING; |
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if (env->comp_irq_trigger & IRQF_TRIGGER_FALLING) |
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env->comp_irq_trigger_inv |= IRQF_TRIGGER_RISING; |
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if (env->comp_irq_trigger & IRQF_TRIGGER_HIGH) |
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env->comp_irq_trigger_inv |= IRQF_TRIGGER_LOW; |
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if (env->comp_irq_trigger & IRQF_TRIGGER_LOW) |
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env->comp_irq_trigger_inv |= IRQF_TRIGGER_HIGH; |
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ret = iio_get_channel_type(env->dac, &type); |
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if (ret < 0) |
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return ret; |
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if (type != IIO_VOLTAGE) { |
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dev_err(dev, "dac is of the wrong type\n"); |
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return -EINVAL; |
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} |
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ret = iio_read_max_channel_raw(env->dac, &env->dac_max); |
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if (ret < 0) { |
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dev_err(dev, "dac does not indicate its raw maximum value\n"); |
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return ret; |
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} |
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return devm_iio_device_register(dev, indio_dev); |
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} |
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static const struct of_device_id envelope_detector_match[] = { |
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{ .compatible = "axentia,tse850-envelope-detector", }, |
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{ /* sentinel */ } |
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}; |
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MODULE_DEVICE_TABLE(of, envelope_detector_match); |
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static struct platform_driver envelope_detector_driver = { |
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.probe = envelope_detector_probe, |
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.driver = { |
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.name = "iio-envelope-detector", |
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.of_match_table = envelope_detector_match, |
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}, |
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}; |
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module_platform_driver(envelope_detector_driver); |
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MODULE_DESCRIPTION("Envelope detector using a DAC and a comparator"); |
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MODULE_AUTHOR("Peter Rosin <[email protected]>"); |
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MODULE_LICENSE("GPL v2");
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