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Fri, 07 Mar 2025 07:11:30 -0800 (PST) Received: from localhost ([2804:30c:1f21:4300:1cf6:c485:6555:b1c5]) by smtp.gmail.com with UTF8SMTPSA id d9443c01a7336-22410a907adsm31000575ad.160.2025.03.07.07.11.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 07 Mar 2025 07:11:29 -0800 (PST) Date: Fri, 7 Mar 2025 12:12:22 -0300 From: Marcelo Schmitt To: Jonathan Santos Cc: linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-gpio@vger.kernel.org, lars@metafoo.de, Michael.Hennerich@analog.com, marcelo.schmitt@analog.com, jic23@kernel.org, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, linus.walleij@linaro.org, brgl@bgdev.pl, lgirdwood@gmail.com, broonie@kernel.org, dlechner@baylibre.com, jonath4nns@gmail.com Subject: Re: [PATCH v4 17/17] iio: adc: ad7768-1: add low pass -3dB cutoff attribute Message-ID: References: <2aa347a97e7ea974951609b0bdf81cad0b21b993.1741268122.git.Jonathan.Santos@analog.com> Precedence: bulk X-Mailing-List: linux-gpio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <2aa347a97e7ea974951609b0bdf81cad0b21b993.1741268122.git.Jonathan.Santos@analog.com> Looks good. Minor comment inline. On 03/06, Jonathan Santos wrote: > Ad7768-1 has a different -3db frequency multiplier depending on > the filter type configured. The cutoff frequency also varies according > to the current ODR. > > Add a readonly low pass -3dB frequency cutoff attribute to clarify to > the user which bandwidth is being allowed depending on the filter > configurations. > > Signed-off-by: Jonathan Santos > --- Reviewed-by: Marcelo Schmitt > v4 Changes: > * None > > v3 Changes: > * None > > v2 Changes: > * New patch in v2. > --- > drivers/iio/adc/ad7768-1.c | 22 ++++++++++++++++++++-- > 1 file changed, 20 insertions(+), 2 deletions(-) > > diff --git a/drivers/iio/adc/ad7768-1.c b/drivers/iio/adc/ad7768-1.c > index 664d0b535340..9ba00e9089bd 100644 > --- a/drivers/iio/adc/ad7768-1.c > +++ b/drivers/iio/adc/ad7768-1.c > @@ -150,6 +150,17 @@ enum ad7768_scan_type { > AD7768_SCAN_TYPE_HIGH_SPEED, > }; > > +/* > + * -3dB cutoff frequency multipliers (relative to ODR) for > + * each filter type. Values are multiplied by 1000. > + */ > +static const int ad7768_filter_3db_odr_multiplier[] = { > + [AD7768_FILTER_SINC5] = 204, > + [AD7768_FILTER_SINC3] = 261, > + [AD7768_FILTER_SINC3_REJ60] = 261, Are these constants from ADAQ7768-1 datasheet? There it says "the sinc3 filter has a −3 dB bandwidth of 0.2617 × ODR." If so, maybe use 262 as SINC3 multiplier? > + [AD7768_FILTER_WIDEBAND] = 433, > +}; > + > static const int ad7768_mclk_div_rates[4] = { > 16, 8, 4, 2, > }; > @@ -228,7 +239,8 @@ static const struct iio_chan_spec ad7768_channels[] = { > .type = IIO_VOLTAGE, > .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), > .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) | > - BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), > + BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) | > + BIT(IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY), > .info_mask_shared_by_type_available = BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), > .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ), > .info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_SAMP_FREQ), > @@ -762,7 +774,7 @@ static int ad7768_read_raw(struct iio_dev *indio_dev, > { > struct ad7768_state *st = iio_priv(indio_dev); > const struct iio_scan_type *scan_type; > - int scale_uv, ret; > + int scale_uv, ret, temp; > > scan_type = iio_get_current_scan_type(indio_dev, chan); > if (IS_ERR(scan_type)) > @@ -802,6 +814,12 @@ static int ad7768_read_raw(struct iio_dev *indio_dev, > case IIO_CHAN_INFO_OVERSAMPLING_RATIO: > *val = st->oversampling_ratio; > > + return IIO_VAL_INT; > + > + case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY: > + temp = st->samp_freq * ad7768_filter_3db_odr_multiplier[st->filter_type]; > + *val = DIV_ROUND_CLOSEST(temp, 1000); > + > return IIO_VAL_INT; > } > > -- > 2.34.1 >