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iio: adc: stm32-dfsdm: fix successive oversampling settings

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When doing successive oversampling settings, it may fail to update filter
parameters silently:
- First time oversampling is being set, it will be successful, as fl->res
is 0 initially.
- Next attempts with various oversamp value may return 0 (success), but
keep previous filter parameters, due to 'res' never reaches above or
equal current 'fl->res'.

This is particularly true when setting sampling frequency (that relies on
oversamp). Typical failure without error:
- run 1st test @16kHz samp freq will succeed
- run new test @8kHz will succeed as well
- run new test @16kHz (again): sample rate will remain 8kHz without error

Fixes: e2e6771c64 ("IIO: ADC: add STM32 DFSDM sigma delta ADC support")

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Acked-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Fabrice Gasnier 2018-03-13 15:23:05 +01:00 committed by Jonathan Cameron
parent 490fba90a9
commit 7531cf59bf
1 changed files with 2 additions and 1 deletions
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3
drivers/iio/adc/stm32-dfsdm-adc.c
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@ -144,6 +144,7 @@ static int stm32_dfsdm_set_osrs(struct stm32_dfsdm_filter *fl,
* Leave as soon as if exact resolution if reached.
* Otherwise the higher resolution below 32 bits is kept.
*/
fl->res = 0;
for (fosr = 1; fosr <= DFSDM_MAX_FL_OVERSAMPLING; fosr++) {
for (iosr = 1; iosr <= DFSDM_MAX_INT_OVERSAMPLING; iosr++) {
if (fast)
@ -193,7 +194,7 @@ static int stm32_dfsdm_set_osrs(struct stm32_dfsdm_filter *fl,
}
}
if (!fl->fosr)
if (!fl->res)
return -EINVAL;
return 0;