1 files changed, 41 insertions, 28 deletions

diff --git a/drivers/iio/humidity/dht11.c b/drivers/iio/humidity/dht11.c
index 623c145d8a97..7d79a1ac5f5f 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;