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

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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Ivan T. Ivanov 2015-04-17 17:51:08 +03:00 committed by Jonathan Cameron
parent d0716b0ea4
commit 937125aca0
1 changed files with 4 additions and 3 deletions
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7
drivers/iio/adc/qcom-spmi-vadc.c
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@ -18,6 +18,7 @@
#include <linux/iio/iio.h> #include <linux/iio/iio.h>
#include <linux/interrupt.h> #include <linux/interrupt.h>
#include <linux/kernel.h> #include <linux/kernel.h>
#include <linux/math64.h>
#include <linux/module.h> #include <linux/module.h>
#include <linux/of.h> #include <linux/of.h>
#include <linux/platform_device.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_channel_prop *prop, u16 adc_code)
{ {
const struct vadc_prescale_ratio *prescale; const struct vadc_prescale_ratio *prescale;
s32 voltage; s64 voltage;
voltage = adc_code - vadc->graph[prop->calibration].gnd; voltage = adc_code - vadc->graph[prop->calibration].gnd;
voltage *= vadc->graph[prop->calibration].dx; 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) if (prop->calibration == VADC_CALIB_ABSOLUTE)
voltage += vadc->graph[prop->calibration].dx; voltage += vadc->graph[prop->calibration].dx;
@ -487,7 +488,7 @@ static s32 vadc_calibrate(struct vadc_priv *vadc,
voltage = voltage * prescale->den; voltage = voltage * prescale->den;
return voltage / prescale->num; return div64_s64(voltage, prescale->num);
} }
static int vadc_decimation_from_dt(u32 value) static int vadc_decimation_from_dt(u32 value)