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path: root/drivers/iio/humidity/dht11.c
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Diffstat (limited to 'drivers/iio/humidity/dht11.c')
-rw-r--r--drivers/iio/humidity/dht11.c69
1 files changed, 41 insertions, 28 deletions
diff --git a/drivers/iio/humidity/dht11.c b/drivers/iio/humidity/dht11.c
index 623c145..7d79a1a 100644
--- a/drivers/iio/humidity/dht11.c
+++ b/drivers/iio/humidity/dht11.c
@@ -29,6 +29,7 @@
#include <linux/wait.h>
#include <linux/bitops.h>
#include <linux/completion.h>
+#include <linux/mutex.h>
#include <linux/delay.h>
#include <linux/gpio.h>
#include <linux/of_gpio.h>
@@ -39,8 +40,12 @@
#define DHT11_DATA_VALID_TIME 2000000000 /* 2s in ns */
-#define DHT11_EDGES_PREAMBLE 4
+#define DHT11_EDGES_PREAMBLE 2
#define DHT11_BITS_PER_READ 40
+/*
+ * Note that when reading the sensor actually 84 edges are detected, but
+ * since the last edge is not significant, we only store 83:
+ */
#define DHT11_EDGES_PER_READ (2*DHT11_BITS_PER_READ + DHT11_EDGES_PREAMBLE + 1)
/* Data transmission timing (nano seconds) */
@@ -57,6 +62,7 @@ struct dht11 {
int irq;
struct completion completion;
+ struct mutex lock;
s64 timestamp;
int temperature;
@@ -88,7 +94,7 @@ static int dht11_decode(struct dht11 *dht11, int offset)
unsigned char temp_int, temp_dec, hum_int, hum_dec, checksum;
/* Calculate timestamp resolution */
- for (i = 0; i < dht11->num_edges; ++i) {
+ for (i = 1; i < dht11->num_edges; ++i) {
t = dht11->edges[i].ts - dht11->edges[i-1].ts;
if (t > 0 && t < timeres)
timeres = t;
@@ -138,6 +144,27 @@ static int dht11_decode(struct dht11 *dht11, int offset)
return 0;
}
+/*
+ * IRQ handler called on GPIO edges
+ */
+static irqreturn_t dht11_handle_irq(int irq, void *data)
+{
+ struct iio_dev *iio = data;
+ struct dht11 *dht11 = iio_priv(iio);
+
+ /* TODO: Consider making the handler safe for IRQ sharing */
+ if (dht11->num_edges < DHT11_EDGES_PER_READ && dht11->num_edges >= 0) {
+ dht11->edges[dht11->num_edges].ts = iio_get_time_ns();
+ dht11->edges[dht11->num_edges++].value =
+ gpio_get_value(dht11->gpio);
+
+ if (dht11->num_edges >= DHT11_EDGES_PER_READ)
+ complete(&dht11->completion);
+ }
+
+ return IRQ_HANDLED;
+}
+
static int dht11_read_raw(struct iio_dev *iio_dev,
const struct iio_chan_spec *chan,
int *val, int *val2, long m)
@@ -145,6 +172,7 @@ static int dht11_read_raw(struct iio_dev *iio_dev,
struct dht11 *dht11 = iio_priv(iio_dev);
int ret;
+ mutex_lock(&dht11->lock);
if (dht11->timestamp + DHT11_DATA_VALID_TIME < iio_get_time_ns()) {
reinit_completion(&dht11->completion);
@@ -157,8 +185,17 @@ static int dht11_read_raw(struct iio_dev *iio_dev,
if (ret)
goto err;
+ ret = request_irq(dht11->irq, dht11_handle_irq,
+ IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+ iio_dev->name, iio_dev);
+ if (ret)
+ goto err;
+
ret = wait_for_completion_killable_timeout(&dht11->completion,
HZ);
+
+ free_irq(dht11->irq, iio_dev);
+
if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) {
dev_err(&iio_dev->dev,
"Only %d signal edges detected\n",
@@ -185,6 +222,7 @@ static int dht11_read_raw(struct iio_dev *iio_dev,
ret = -EINVAL;
err:
dht11->num_edges = -1;
+ mutex_unlock(&dht11->lock);
return ret;
}
@@ -193,27 +231,6 @@ static const struct iio_info dht11_iio_info = {
.read_raw = dht11_read_raw,
};
-/*
- * IRQ handler called on GPIO edges
-*/
-static irqreturn_t dht11_handle_irq(int irq, void *data)
-{
- struct iio_dev *iio = data;
- struct dht11 *dht11 = iio_priv(iio);
-
- /* TODO: Consider making the handler safe for IRQ sharing */
- if (dht11->num_edges < DHT11_EDGES_PER_READ && dht11->num_edges >= 0) {
- dht11->edges[dht11->num_edges].ts = iio_get_time_ns();
- dht11->edges[dht11->num_edges++].value =
- gpio_get_value(dht11->gpio);
-
- if (dht11->num_edges >= DHT11_EDGES_PER_READ)
- complete(&dht11->completion);
- }
-
- return IRQ_HANDLED;
-}
-
static const struct iio_chan_spec dht11_chan_spec[] = {
{ .type = IIO_TEMP,
.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), },
@@ -256,11 +273,6 @@ static int dht11_probe(struct platform_device *pdev)
dev_err(dev, "GPIO %d has no interrupt\n", dht11->gpio);
return -EINVAL;
}
- ret = devm_request_irq(dev, dht11->irq, dht11_handle_irq,
- IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
- pdev->name, iio);
- if (ret)
- return ret;
dht11->timestamp = iio_get_time_ns() - DHT11_DATA_VALID_TIME - 1;
dht11->num_edges = -1;
@@ -268,6 +280,7 @@ static int dht11_probe(struct platform_device *pdev)
platform_set_drvdata(pdev, iio);
init_completion(&dht11->completion);
+ mutex_init(&dht11->lock);
iio->name = pdev->name;
iio->dev.parent = &pdev->dev;
iio->info = &dht11_iio_info;
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