iio: dht11: Use boottime

Wall time obtained from ktime_get_real_ns is susceptible to sudden jumps due to
user setting the time or due to NTP.  Boot time is constantly increasing time
better suited for comparing two timestamps.

Signed-off-by: Abhilash Jindal <klock.android@gmail.com>
Reviewed-by: Harald Geyer <harald@ccbib.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/iio/humidity/dht11.c b/drivers/iio/humidity/dht11.c
index 1165b1c..cfc5a05 100644 (file)
--- a/drivers/iio/humidity/dht11.c
+++ b/drivers/iio/humidity/dht11.c
@@ -117,7 +117,7 @@ static int dht11_decode(struct dht11 *dht11, int offset, int timeres)
        if (((hum_int + hum_dec + temp_int + temp_dec) & 0xff) != checksum)
                return -EIO;
 
-       dht11->timestamp = ktime_get_real_ns();
+       dht11->timestamp = ktime_get_boot_ns();
        if (hum_int < 20) {  /* DHT22 */
                dht11->temperature = (((temp_int & 0x7f) << 8) + temp_dec) *
                                        ((temp_int & 0x80) ? -100 : 100);
@@ -145,7 +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 = ktime_get_real_ns();
+               dht11->edges[dht11->num_edges].ts = ktime_get_boot_ns();
                dht11->edges[dht11->num_edges++].value =
                                                gpio_get_value(dht11->gpio);
 
@@ -164,7 +164,7 @@ static int dht11_read_raw(struct iio_dev *iio_dev,
        int ret, timeres;
 
        mutex_lock(&dht11->lock);
-       if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_real_ns()) {
+       if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_boot_ns()) {
                timeres = ktime_get_resolution_ns();
                if (DHT11_DATA_BIT_HIGH < 2 * timeres) {
                        dev_err(dht11->dev, "timeresolution %dns too low\n",
@@ -279,7 +279,7 @@ static int dht11_probe(struct platform_device *pdev)
                return -EINVAL;
        }
 
-       dht11->timestamp = ktime_get_real_ns() - DHT11_DATA_VALID_TIME - 1;
+       dht11->timestamp = ktime_get_boot_ns() - DHT11_DATA_VALID_TIME - 1;
        dht11->num_edges = -1;
 
        platform_set_drvdata(pdev, iio);