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SubjectRe: [PATCH] iio: adc: spmi-vadc: Fix overflow in output value normalization
On 17/04/15 15:51, Ivan T. Ivanov wrote:
> 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>
Applied to the fixes-togreg branch of iio.git and marked for stable.

Thanks,

Jonathan
>
> ---
> 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
>
> --
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