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B, page 25, RESET section) says: "When a reset is initiated, the user must allow a period of 500 us before accessing any of the on-chip registers." Use fsleep(500) instead of usleep_range(500, 2000). The 500 us minimum stays the same; fsleep() picks the upper slack itself (about +25% on a default config -- narrower than the original 2000 us). Add a code comment with the datasheet reference so the "why" of the wait is visible at the call site. Signed-off-by: Stepan Ionichev --- drivers/iio/adc/ad7793.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/iio/adc/ad7793.c b/drivers/iio/adc/ad7793.c index 8ff7b70d6..dbc6b47b7 100644 --- a/drivers/iio/adc/ad7793.c +++ b/drivers/iio/adc/ad7793.c @@ -268,7 +268,12 @@ static int ad7793_setup(struct iio_dev *indio_dev, ret = ad_sd_reset(&st->sd); if (ret < 0) goto out; - usleep_range(500, 2000); /* Wait for at least 500us */ + + /* + * Per AD7792/AD7793 datasheet (Rev. B, page 25, RESET section), + * allow 500 us after a reset before accessing on-chip registers. + */ + fsleep(500); /* write/read test for device presence */ ret = ad_sd_read_reg(&st->sd, AD7793_REG_ID, 1, &id); -- 2.43.0