diff mbox

iio: adc: spmi-vadc: Fix overflow in output value normalization

Message ID 1429282268-30501-1-git-send-email-ivan.ivanov@linaro.org
State New
Headers show

Commit Message

Ivan T. Ivanov April 17, 2015, 2:51 p.m. UTC 
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(-)

--
1.9.1

--
To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
diff mbox

Patch

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)