diff options
Diffstat (limited to 'drivers/iio/humidity/dht11.c')
| -rw-r--r-- | drivers/iio/humidity/dht11.c | 65 |
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); |