Hi Jonathan!
Jonathan Cameron writes:
> On 07/04/15 12:12, Harald Geyer wrote:
> > This cleans up the most ugly workaround in this driver. There are no
> > functional changes yet in the decoding algorithm, but we improve the
> > following things:
> > * Get rid of spurious warning messages on systems with fast HRTIMER.
> > * If the clock is not fast enough for decoding to work, we give
> > up immediately.
> > * In that case we return EAGAIN instead of EIO, so it's easier to
> > discriminate causes of failure.
> >
> > Returning EAGAIN is somewhat controversial: It's technically correct
> > as a faster clock might become available. OTOH once all clocks are
> > enabled this is a permanent error. There is no ECLOCKTOOSLOW error
> > code.
> >
> > Signed-off-by: Harald Geyer <harald@xxxxxxxxx>
> Looks good to me. Will wait for comments on the first patch though
> before taking this... clearly that one will need a few acks if I take
> it through IIO!
The first patch has been merged via tip tree for 4.2 (is already available
in staging-next tree). Are you going to pick up this patch or do I need
to resend?
Thanks,
Harald
> Jonathan
> > ---
> > changes since V1:
> > call ktime_get_xxx() functions directly instead of using the wrappers
> > of the iio subsystem.
> >
> > drivers/iio/humidity/dht11.c | 42 ++++++++++++++++++++++--------------------
> > 1 files changed, 22 insertions(+), 20 deletions(-)
> >
> > diff --git a/drivers/iio/humidity/dht11.c b/drivers/iio/humidity/dht11.c
> > index 7d79a1a..4cb25dc 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>
> >
> > @@ -87,23 +88,11 @@ 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)
> > pr_err("dht11: WARNING: decoding ambiguous\n");
> > @@ -126,7 +115,7 @@ 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 +143,7 @@ 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);
> >
> > @@ -170,10 +159,22 @@ static int dht11_read_raw(struct iio_dev *iio_dev,
> > 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;
> > @@ -208,7 +209,8 @@ static int dht11_read_raw(struct iio_dev *iio_dev,
> > ret = dht11_decode(dht11,
> > dht11->num_edges == DHT11_EDGES_PER_READ ?
> > DHT11_EDGES_PREAMBLE :
> > - DHT11_EDGES_PREAMBLE - 2);
> > + DHT11_EDGES_PREAMBLE - 2,
> > + timeres);
> > if (ret)
> > goto err;
> > }
> > @@ -274,7 +276,7 @@ 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);
> >
>
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