Messages in this thread Patch in this message | | | From | "Ivan T. Ivanov" <> | Subject | [PATCH] iio: adc: spmi-vadc: Fix overflow in output value normalization | Date | Fri, 17 Apr 2015 17:51:08 +0300 |
| |
With 'dx' equal to 0.625V and 15 bit ADC, calculations overflow when difference against GND is ~20% of the ADC range. Fix this.
Signed-off-by: Ivan T. Ivanov <ivan.ivanov@linaro.org> --- drivers/iio/adc/qcom-spmi-vadc.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/iio/adc/qcom-spmi-vadc.c b/drivers/iio/adc/qcom-spmi-vadc.c index 3211729..0c4618b 100644 --- a/drivers/iio/adc/qcom-spmi-vadc.c +++ b/drivers/iio/adc/qcom-spmi-vadc.c @@ -18,6 +18,7 @@ #include <linux/iio/iio.h> #include <linux/interrupt.h> #include <linux/kernel.h> +#include <linux/math64.h> #include <linux/module.h> #include <linux/of.h> #include <linux/platform_device.h> @@ -471,11 +472,11 @@ static s32 vadc_calibrate(struct vadc_priv *vadc, const struct vadc_channel_prop *prop, u16 adc_code) { const struct vadc_prescale_ratio *prescale; - s32 voltage; + s64 voltage;
voltage = adc_code - vadc->graph[prop->calibration].gnd; voltage *= vadc->graph[prop->calibration].dx; - voltage = voltage / vadc->graph[prop->calibration].dy; + voltage = div64_s64(voltage, vadc->graph[prop->calibration].dy);
if (prop->calibration == VADC_CALIB_ABSOLUTE) voltage += vadc->graph[prop->calibration].dx; @@ -487,7 +488,7 @@ static s32 vadc_calibrate(struct vadc_priv *vadc,
voltage = voltage * prescale->den;
- return voltage / prescale->num; + return div64_s64(voltage, prescale->num); }
static int vadc_decimation_from_dt(u32 value) -- 1.9.1
| |