The AD7949 requires two conversion cycles following the first configuration change, and one extra cycle following any other configuration change (including changing the analog channel being sampled). Therefore, adding a dummy read cycle when config is changed and removing the extra cycle at initial configuration (the first dummy cycle is now performed as part of applying the configuration change). Signed-off-by: Adam Michaelis <adam.michaelis@xxxxxxxxxxxxxxxxxxx> --- V2: - Add some defines to reduce use of magic numbers. V3: - Switch back to using a u32 data buffer. - Add-back the second dummy cycle on initialization. - Move to first patch in series. --- drivers/iio/adc/ad7949.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c index ac0ffff6c5ae..c7fe27aa2519 100644 --- a/drivers/iio/adc/ad7949.c +++ b/drivers/iio/adc/ad7949.c @@ -100,6 +100,23 @@ static int ad7949_spi_write_cfg(struct ad7949_adc_chip *ad7949_adc, u16 val, * send a new command to the device */ udelay(2); + + /* + * Perform extra read cycle to allow configuration, acquisition, + * and conversion sequences to complete for new configuration. + */ + ad7949_adc->buffer = 0; + + spi_message_init_with_transfers(&msg, tx, 1); + + ret = spi_sync(ad7949_adc->spi, &msg); + + /* + * This delay is to avoid a new request before the required time + * to send a new command to the device. + */ + udelay(2); + return ret; } @@ -229,11 +246,10 @@ static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc) ret = ad7949_spi_write_cfg(ad7949_adc, 0x3C79, AD7949_MASK_TOTAL); /* - * Do two dummy conversions to apply the first configuration setting. + * Do a dummy conversion to apply the first configuration setting. * Required only after the start up of the device. */ ad7949_spi_read_channel(ad7949_adc, &val, ad7949_adc->current_channel); - ad7949_spi_read_channel(ad7949_adc, &val, ad7949_adc->current_channel); return ret; } -- 1.9.1
