diff options
Diffstat (limited to 'meta-openbmc-mods/meta-common/recipes-kernel/linux/linux-aspeed/1002-Filter-erroneous-adc-readings.patch')
| -rw-r--r-- | meta-openbmc-mods/meta-common/recipes-kernel/linux/linux-aspeed/1002-Filter-erroneous-adc-readings.patch | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/meta-openbmc-mods/meta-common/recipes-kernel/linux/linux-aspeed/1002-Filter-erroneous-adc-readings.patch b/meta-openbmc-mods/meta-common/recipes-kernel/linux/linux-aspeed/1002-Filter-erroneous-adc-readings.patch new file mode 100644 index 000000000..9306ca9e2 --- /dev/null +++ b/meta-openbmc-mods/meta-common/recipes-kernel/linux/linux-aspeed/1002-Filter-erroneous-adc-readings.patch @@ -0,0 +1,59 @@ +From 8188c4d5deda1d747801bfafb750fd61d0292ba5 Mon Sep 17 00:00:00 2001 +From: Zhikui Ren <zhikui.ren@intel.com> +Date: Tue, 13 Oct 2020 12:23:29 -0700 +Subject: [PATCH] Filter erroneous adc readings + +There has been cases that ast2500 ADC appears to return an incorrect +reading. Re-read the ADC data once if the ADC valuse jumped more than +80 counts comparing the previous value. + +This is a workaround to filter out these erroneous readings recorded +from user space application polling every second: +PVNN_PCH_AUX history dump: + 0.9,0.9,0.9,0.9,1.351,0.9,0.9,0.9,0.901,0.898 +PVDQ_DEF_CPU1 history dump: + 1.235,1.237,1.237,1.235,1.348,1.237,1.237,1.235,1.237,1.235 +ADC raw reading is 1000 times above numbers. + +This approach works if there is a silicon bug in adc register read +with minimal risk. It will not work if the bad readings come from noise +in the sensing circuitry. This patch may be removed if that is proven +to be the case. + +Tested: +Build and verified no regression in voltage reading on my WC. + +Signed-off-by: Zhikui Ren <zhikui.ren@intel.com> +--- + drivers/iio/adc/aspeed_adc.c | 8 ++++++++ + 1 file changed, 8 insertions(+) + +diff --git a/drivers/iio/adc/aspeed_adc.c b/drivers/iio/adc/aspeed_adc.c +index c115797c4cc5..c1e775e764ca 100644 +--- a/drivers/iio/adc/aspeed_adc.c ++++ b/drivers/iio/adc/aspeed_adc.c +@@ -55,6 +55,7 @@ + + #define ASPEED_ADC_CHANNELS_MAX 16 + #define ASPEED_ADC_RAW_VALUE_MAX 0x3ff ++#define ASPEED_ADC_RAW_VALUE_DELTA_THRESHOLD 80 + + struct aspeed_adc_model_data { + const char *model_name; +@@ -133,6 +134,13 @@ static int aspeed_adc_read_raw(struct iio_dev *indio_dev, + pr_err("aspeed_adc: channel %d drop invalid raw reading 0x3FF %d\n", + chan->channel, ASPEED_ADC_RAW_VALUE_MAX); + } else { ++ if (*val > (data->channel_raw_value[chan->channel] + ++ ASPEED_ADC_RAW_VALUE_DELTA_THRESHOLD)) { ++ pr_err("aspeed_adc: Warning-channel %d prev=%d, curr=%d, retry.\n", ++ chan->channel, ++ data->channel_raw_value[chan->channel], *val); ++ *val = readw(data->base + chan->address); ++ } + data->channel_raw_value[chan->channel] = *val; + } + return IIO_VAL_INT; +-- +2.17.1 + |