4.16-stable review patch. If anyone has any objections, please let me know.
------------------
From: Fabrice Gasnier fabrice.gasnier@st.com
commit 7531cf59bfa082769887ec70c2029838ea139f11 upstream.
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: e2e6771c6462 ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/iio/adc/stm32-dfsdm-adc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/iio/adc/stm32-dfsdm-adc.c +++ b/drivers/iio/adc/stm32-dfsdm-adc.c @@ -144,6 +144,7 @@ static int stm32_dfsdm_set_osrs(struct s * 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 s } }
- if (!fl->fosr) + if (!fl->res) return -EINVAL;
return 0;