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[98.183.112.25]) by smtp.gmail.com with ESMTPSA id 006d021491bc7-5fa8b528e63sm2605288eaf.8.2025.01.27.17.27.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Jan 2025 17:27:45 -0800 (PST) Message-ID: Date: Mon, 27 Jan 2025 19:27:43 -0600 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 16/16] iio: adc: ad7768-1: add low pass -3dB cutoff attribute To: Jonathan Santos , linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Cc: 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, jonath4nns@gmail.com, marcelo.schmitt1@gmail.com References: <91b697b66a42ead9e05dd4e79d6fb1e776c569d6.1737985435.git.Jonathan.Santos@analog.com> From: David Lechner Content-Language: en-US In-Reply-To: <91b697b66a42ead9e05dd4e79d6fb1e776c569d6.1737985435.git.Jonathan.Santos@analog.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/27/25 9:14 AM, 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 > --- > v2 Changes: > * New patch in v2. > --- > drivers/iio/adc/ad7768-1.c | 23 +++++++++++++++++++++-- > 1 file changed, 21 insertions(+), 2 deletions(-) > > diff --git a/drivers/iio/adc/ad7768-1.c b/drivers/iio/adc/ad7768-1.c > index 6d0b430a8d54..daf91ef6f77b 100644 > --- a/drivers/iio/adc/ad7768-1.c > +++ b/drivers/iio/adc/ad7768-1.c > @@ -149,6 +149,18 @@ 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[] = { > + [SINC5] = 204, > + [SINC5_DEC_X8] = 204, > + [SINC5_DEC_X16] = 204, > + [SINC3] = 261, > + [WIDEBAND] = 433, > +}; > + > static const int ad7768_mclk_div_rates[4] = { > 16, 8, 4, 2, > }; > @@ -202,7 +214,8 @@ static const struct iio_chan_spec ad7768_channels[] = { > .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), > .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), > .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ) | > - BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), > + BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) | > + BIT(IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY), > .ext_info = ad7768_ext_info, > .indexed = 1, > .channel = 0, > @@ -802,7 +815,7 @@ 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)) > @@ -842,6 +855,12 @@ 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; > } > If this is read-only, do we actually need it? It looks like the attribute is going to return 1 of 3 values that exactly matches the filter_type attribute, so this is not really giving any additional info.