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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.c65
1 files changed, 35 insertions, 30 deletions
diff --git a/drivers/iio/humidity/dht11.c b/drivers/iio/humidity/dht11.c
index 7d79a1ac5..1165b1c4f 100644
--- a/drivers/iio/humidity/dht11.c
+++ b/drivers/iio/humidity/dht11.c
@@ -33,6 +33,7 @@
#include <linux/delay.h>
#include <linux/gpio.h>
#include <linux/of_gpio.h>
+#include <linux/timekeeping.h>
#include <linux/iio/iio.h>
@@ -46,7 +47,8 @@
* 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)
+#define DHT11_EDGES_PER_READ (2 * DHT11_BITS_PER_READ + \
+ DHT11_EDGES_PREAMBLE + 1)
/* Data transmission timing (nano seconds) */
#define DHT11_START_TRANSMISSION 18 /* ms */
@@ -62,6 +64,7 @@ struct dht11 {
int irq;
struct completion completion;
+ /* The iio sysfs interface doesn't prevent concurrent reads: */
struct mutex lock;
s64 timestamp;
@@ -87,32 +90,20 @@ static unsigned char dht11_decode_byte(int *timing, int threshold)
return ret;
}
-static int dht11_decode(struct dht11 *dht11, int offset)
+static int dht11_decode(struct dht11 *dht11, int offset, int timeres)
{
- int i, t, timing[DHT11_BITS_PER_READ], threshold,
- timeres = DHT11_SENSOR_RESPONSE;
+ int i, t, timing[DHT11_BITS_PER_READ], threshold;
unsigned char temp_int, temp_dec, hum_int, hum_dec, checksum;
- /* Calculate timestamp resolution */
- 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;
- }
- if (2*timeres > DHT11_DATA_BIT_HIGH) {
- pr_err("dht11: timeresolution %d too bad for decoding\n",
- timeres);
- return -EIO;
- }
threshold = DHT11_DATA_BIT_HIGH / timeres;
- if (DHT11_DATA_BIT_LOW/timeres + 1 >= threshold)
+ if (DHT11_DATA_BIT_LOW / timeres + 1 >= threshold)
pr_err("dht11: WARNING: decoding ambiguous\n");
/* scale down with timeres and check validity */
for (i = 0; i < DHT11_BITS_PER_READ; ++i) {
- t = dht11->edges[offset + 2*i + 2].ts -
- dht11->edges[offset + 2*i + 1].ts;
- if (!dht11->edges[offset + 2*i + 1].value)
+ t = dht11->edges[offset + 2 * i + 2].ts -
+ dht11->edges[offset + 2 * i + 1].ts;
+ if (!dht11->edges[offset + 2 * i + 1].value)
return -EIO; /* lost synchronisation */
timing[i] = t / timeres;
}
@@ -126,7 +117,7 @@ static int dht11_decode(struct dht11 *dht11, int offset)
if (((hum_int + hum_dec + temp_int + temp_dec) & 0xff) != checksum)
return -EIO;
- dht11->timestamp = iio_get_time_ns();
+ dht11->timestamp = ktime_get_real_ns();
if (hum_int < 20) { /* DHT22 */
dht11->temperature = (((temp_int & 0x7f) << 8) + temp_dec) *
((temp_int & 0x80) ? -100 : 100);
@@ -154,7 +145,7 @@ static irqreturn_t dht11_handle_irq(int irq, void *data)
/* 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].ts = ktime_get_real_ns();
dht11->edges[dht11->num_edges++].value =
gpio_get_value(dht11->gpio);
@@ -166,14 +157,26 @@ static irqreturn_t dht11_handle_irq(int irq, void *data)
}
static int dht11_read_raw(struct iio_dev *iio_dev,
- const struct iio_chan_spec *chan,
+ const struct iio_chan_spec *chan,
int *val, int *val2, long m)
{
struct dht11 *dht11 = iio_priv(iio_dev);
- int ret;
+ int ret, timeres;
mutex_lock(&dht11->lock);
- if (dht11->timestamp + DHT11_DATA_VALID_TIME < iio_get_time_ns()) {
+ if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_real_ns()) {
+ timeres = ktime_get_resolution_ns();
+ if (DHT11_DATA_BIT_HIGH < 2 * timeres) {
+ dev_err(dht11->dev, "timeresolution %dns too low\n",
+ timeres);
+ /* In theory a better clock could become available
+ * at some point ... and there is no error code
+ * that really fits better.
+ */
+ ret = -EAGAIN;
+ goto err;
+ }
+
reinit_completion(&dht11->completion);
dht11->num_edges = 0;
@@ -192,13 +195,13 @@ static int dht11_read_raw(struct iio_dev *iio_dev,
goto err;
ret = wait_for_completion_killable_timeout(&dht11->completion,
- HZ);
+ 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",
+ "Only %d signal edges detected\n",
dht11->num_edges);
ret = -ETIMEDOUT;
}
@@ -206,9 +209,10 @@ static int dht11_read_raw(struct iio_dev *iio_dev,
goto err;
ret = dht11_decode(dht11,
- dht11->num_edges == DHT11_EDGES_PER_READ ?
+ dht11->num_edges == DHT11_EDGES_PER_READ ?
DHT11_EDGES_PREAMBLE :
- DHT11_EDGES_PREAMBLE - 2);
+ DHT11_EDGES_PREAMBLE - 2,
+ timeres);
if (ret)
goto err;
}
@@ -261,9 +265,10 @@ static int dht11_probe(struct platform_device *pdev)
dht11 = iio_priv(iio);
dht11->dev = dev;
- dht11->gpio = ret = of_get_gpio(node, 0);
+ ret = of_get_gpio(node, 0);
if (ret < 0)
return ret;
+ dht11->gpio = ret;
ret = devm_gpio_request_one(dev, dht11->gpio, GPIOF_IN, pdev->name);
if (ret)
return ret;
@@ -274,7 +279,7 @@ static int dht11_probe(struct platform_device *pdev)
return -EINVAL;
}
- dht11->timestamp = iio_get_time_ns() - DHT11_DATA_VALID_TIME - 1;
+ dht11->timestamp = ktime_get_real_ns() - DHT11_DATA_VALID_TIME - 1;
dht11->num_edges = -1;
platform_set_drvdata(pdev, iio);