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([2600:8803:e7e4:1d00:fdf1:f11e:e330:d3c1]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-7524986ca64sm1037256a34.14.2025.09.12.07.25.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 12 Sep 2025 07:25:42 -0700 (PDT) Message-ID: <889408fb-e7c5-4a1e-be96-1f632e97469e@baylibre.com> Date: Fri, 12 Sep 2025 09:25:41 -0500 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/6] iio: adc: ad7124: support fractional sampling_frequency To: Andy Shevchenko Cc: Michael Hennerich , Jonathan Cameron , =?UTF-8?Q?Nuno_S=C3=A1?= , Andy Shevchenko , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250911-iio-adc-ad7124-add-filter-support-v2-0-b09f492416c7@baylibre.com> <20250911-iio-adc-ad7124-add-filter-support-v2-4-b09f492416c7@baylibre.com> Content-Language: en-US From: David Lechner In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 9/11/25 11:45 PM, Andy Shevchenko wrote: > On Fri, Sep 12, 2025 at 12:42 AM David Lechner wrote: >> >> Modify the attribute read/write functions for sampling_frequency and >> filter_low_pass_3db_frequency to return fractional values. >> >> These ADCs support output data rates in the single digits, so being >> able to specify fractional values is necessary to use all possible >> sampling frequencies. > > ... > >> factor = 32 * 4; /* N = 4 for default sinc4 filter. */ >> - odr_sel_bits = clamp(DIV_ROUND_CLOSEST(fclk, odr * factor), 1, 2047); >> + odr_sel_bits = DIV_ROUND_CLOSEST(fclk, odr * factor + >> + odr_micro * factor / MICRO); > >> + odr_sel_bits = clamp(odr_sel_bits, 1, 2047); > > I would rather see this clamp() call to be the part of > cfg.odr_sel_bits() assignment, otherwise the above line and this > operate on the semantically (slightly) different data. So, the first > line should use different variable name, or the second, like > odr_sel_bits_clamped. If we moved it, then we would unnecessarily clear the cfg.live bit in cases where clamping changed the value. In a later commit, this gets combined to a single assignment so not much point in adding a 2nd variable temporarily. > >> if (odr_sel_bits != st->channels[channel].cfg.odr_sel_bits) >> st->channels[channel].cfg.live = false; >> >> - /* fADC = fCLK / (FS[10:0] x 32) */ >> - st->channels[channel].cfg.odr = DIV_ROUND_CLOSEST(fclk, odr_sel_bits * >> - factor); >> st->channels[channel].cfg.odr_sel_bits = odr_sel_bits; > >