When reading registers on the AD2S1210 chip, we have to supply a "dummy" address for the second SPI tx byte so that we don't accidentally write to a register. This register will be read and the value discarded on the next regmap read or write call. Reading the fault register has a side-effect of clearing the faults so we should not use this register for the dummy read. Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx> --- v4 changes: New patch (this probably should have been done before "staging: iio: resolver: ad2s1210: use regmap for config registers" but was overlooked until now) drivers/staging/iio/resolver/ad2s1210.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/staging/iio/resolver/ad2s1210.c b/drivers/staging/iio/resolver/ad2s1210.c index 67d8af0dd7ae..8fbde9517fe9 100644 --- a/drivers/staging/iio/resolver/ad2s1210.c +++ b/drivers/staging/iio/resolver/ad2s1210.c @@ -166,9 +166,10 @@ static int ad2s1210_regmap_reg_read(void *context, unsigned int reg, st->tx[0] = reg; /* * Must be valid register address here otherwise this could write data. - * It doesn't matter which one. + * It doesn't matter which one as long as reading doesn't have side- + * effects. */ - st->tx[1] = AD2S1210_REG_FAULT; + st->tx[1] = AD2S1210_REG_CONTROL; ret = spi_sync_transfer(st->sdev, xfers, ARRAY_SIZE(xfers)); if (ret < 0) -- 2.42.0
