diff options
author | Marcel Ziswiler <marcel.ziswiler@toradex.com> | 2019-12-18 22:52:20 +0100 |
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committer | Marcel Ziswiler <marcel.ziswiler@toradex.com> | 2019-12-18 22:52:20 +0100 |
commit | 1ddf624b0b268fdc0b80b1de618b98f8d117afea (patch) | |
tree | 3d3218332bcb34cb0afa01d6ad996058a3dbcb77 /drivers/iio/proximity/srf04.c | |
parent | 6b774eec1f9d3064e9b33634dfa99d5666d0a73a (diff) | |
parent | bfb9e5c03076a446b1f4f6a523ddc8d723c907a6 (diff) |
Merge tag 'v4.14.159' into 4.14-2.0.x-imx
This is the 4.14.159 stable release
Conflicts:
arch/arm/Kconfig.debug
arch/arm/boot/dts/imx7s.dtsi
arch/arm/mach-imx/cpuidle-imx6sx.c
drivers/crypto/caam/caamalg.c
drivers/crypto/mxs-dcp.c
drivers/dma/imx-sdma.c
drivers/input/keyboard/imx_keypad.c
drivers/net/can/flexcan.c
drivers/net/can/rx-offload.c
drivers/net/wireless/ath/ath10k/pci.c
drivers/pci/dwc/pci-imx6.c
drivers/spi/spi-fsl-lpspi.c
drivers/usb/dwc3/gadget.c
Diffstat (limited to 'drivers/iio/proximity/srf04.c')
-rw-r--r-- | drivers/iio/proximity/srf04.c | 29 |
1 files changed, 15 insertions, 14 deletions
diff --git a/drivers/iio/proximity/srf04.c b/drivers/iio/proximity/srf04.c index e37667f933b3..8a6ab9691832 100644 --- a/drivers/iio/proximity/srf04.c +++ b/drivers/iio/proximity/srf04.c @@ -105,7 +105,7 @@ static int srf04_read(struct srf04_data *data) udelay(10); 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); @@ -115,7 +115,8 @@ 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; @@ -130,19 +131,19 @@ 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; @@ -154,20 +155,20 @@ 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; } |