On Wed, 26 Jun 2019 20:59:08 +0200 Zbyněk Kocur <[email protected]> wrote:
> Hello, Andreas, > > Your patch seems to solve my question. I haven't had time to test it because > of holidays. I'll test it as soon as possible. No rush, it's a clear fix anyway so we can queue this up in the rc phase of the next kernel cycle! Thanks, Jonathan > > Zbyněk > --- > email: [email protected] > phone: +420 224 354 054 > web: http://www.fel.cvut.cz > Department of Telecommunications Engineering > Faculty of Electrical Engineering > > > On 26 Jun 2019, at 20:21, Jonathan Cameron <[email protected]> wrote: > > > > On Sun, 23 Jun 2019 14:29:10 +0200 > > Andreas Klinger <[email protected]> wrote: > > > >> The measured time value in the driver is limited to the maximum distance > >> which can be read by the sensor. This limitation was wrong and is fixed > >> by this patch. > >> > >> It also takes into account that we are supporting a variety of sensors > >> today and that the recently added sensors have a higher maximum > >> distance range. > >> > >> Suggested-by: Zbyněk Kocur <[email protected]> > >> Signed-off-by: Andreas Klinger <[email protected]> > > Ideally I'm looking for Zbyněk to confirm that this addresses the > > original question. > > > > Thanks, > > > > Jonathan > > > >> --- > >> drivers/iio/proximity/srf04.c | 29 +++++++++++++++-------------- > >> 1 file changed, 15 insertions(+), 14 deletions(-) > >> > >> diff --git a/drivers/iio/proximity/srf04.c b/drivers/iio/proximity/srf04.c > >> index 8b50d56b0a03..01eb8cc63076 100644 > >> --- a/drivers/iio/proximity/srf04.c > >> +++ b/drivers/iio/proximity/srf04.c > >> @@ -110,7 +110,7 @@ static int srf04_read(struct srf04_data *data) > >> udelay(data->cfg->trigger_pulse_us); > >> gpiod_set_value(data->gpiod_trig, 0); > >> > >> - /* it cannot take more than 20 ms */ > >> + /* it should not take more than 20 ms until echo is rising */ > >> ret = wait_for_completion_killable_timeout(&data->rising, HZ/50); > >> if (ret < 0) { > >> mutex_unlock(&data->lock); > >> @@ -120,7 +120,8 @@ static int srf04_read(struct srf04_data *data) > >> return -ETIMEDOUT; > >> } > >> > >> - ret = wait_for_completion_killable_timeout(&data->falling, HZ/50); > >> + /* it cannot take more than 50 ms until echo is falling */ > >> + ret = wait_for_completion_killable_timeout(&data->falling, HZ/20); > >> if (ret < 0) { > >> mutex_unlock(&data->lock); > >> return ret; > >> @@ -135,19 +136,19 @@ static int srf04_read(struct srf04_data *data) > >> > >> dt_ns = ktime_to_ns(ktime_dt); > >> /* > >> - * measuring more than 3 meters is beyond the capabilities of > >> - * the sensor > >> + * measuring more than 6,45 meters is beyond the capabilities of > >> + * the supported sensors > >> * ==> filter out invalid results for not measuring echos of > >> * another us sensor > >> * > >> * formula: > >> - * distance 3 m > >> - * time = ---------- = --------- = 9404389 ns > >> - * speed 319 m/s > >> + * distance 6,45 * 2 m > >> + * time = ---------- = ------------ = 40438871 ns > >> + * speed 319 m/s > >> * > >> * using a minimum speed at -20 °C of 319 m/s > >> */ > >> - if (dt_ns > 9404389) > >> + if (dt_ns > 40438871) > >> return -EIO; > >> > >> time_ns = dt_ns; > >> @@ -159,20 +160,20 @@ static int srf04_read(struct srf04_data *data) > >> * with Temp in °C > >> * and speed in m/s > >> * > >> - * use 343 m/s as ultrasonic speed at 20 °C here in absence of the > >> + * use 343,5 m/s as ultrasonic speed at 20 °C here in absence of the > >> * temperature > >> * > >> * therefore: > >> - * time 343 > >> - * distance = ------ * ----- > >> - * 10^6 2 > >> + * time 343,5 time * 106 > >> + * distance = ------ * ------- = ------------ > >> + * 10^6 2 617176 > >> * with time in ns > >> * and distance in mm (one way) > >> * > >> - * because we limit to 3 meters the multiplication with 343 just > >> + * because we limit to 6,45 meters the multiplication with 106 just > >> * fits into 32 bit > >> */ > >> - distance_mm = time_ns * 343 / 2000000; > >> + distance_mm = time_ns * 106 / 617176; > >> > >> return distance_mm; > >> } > > >
