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Sat, 14 Mar 2026 10:20:18 -0700 (PDT) From: Neel Bullywon To: lars@metafoo.de, Michael.Hennerich@analog.com, jic23@kernel.org Cc: dlechner@baylibre.com, nuno.sa@analog.com, andy@kernel.org, linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, Neel Bullywon Subject: [PATCH v2] iio: frequency: adf4350: replace loop with fls_long() Date: Sat, 14 Mar 2026 13:20:06 -0400 Message-ID: <20260314172006.69744-1-neelb2403@gmail.com> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20260311020115.56321-1-neelb2403@gmail.com> References: <20260311020115.56321-1-neelb2403@gmail.com> Precedence: bulk X-Mailing-List: linux-iio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Address the TODO in adf4350_set_freq() by replacing the iterative power-of-2 shift loop with a constant-time bitwise calculation. By comparing the highest set bits of the target constant and freq using fls_long(), we can calculate the required RF divider selection in a single step without relying on expensive 64-bit division. This ensures freq is properly shifted to meet or exceed the minimum VCO frequency. Signed-off-by: Neel Bullywon --- Changes in v2: - Use fls_long() instead of order_base_2(DIV_ROUND_UP_ULL()) to avoid unnecessary 64-bit division (Andy Shevchenko) - Add correction check for mantissa edge case - Adjust whitespace per review feedback drivers/iio/frequency/adf4350.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/drivers/iio/frequency/adf4350.c b/drivers/iio/frequency/adf4350.c index ed1741165f55..2183deec179d 100644 --- a/drivers/iio/frequency/adf4350.c +++ b/drivers/iio/frequency/adf4350.c @@ -17,6 +17,7 @@ #include #include #include +#include #include #include #include @@ -151,17 +152,14 @@ static int adf4350_set_freq(struct adf4350_state *st, unsigned long long freq) st->r4_rf_div_sel = 0; - /* - * !\TODO: The below computation is making sure we get a power of 2 - * shift (st->r4_rf_div_sel) so that freq becomes higher or equal to - * ADF4350_MIN_VCO_FREQ. This might be simplified with fls()/fls_long() - * and friends. - */ - while (freq < ADF4350_MIN_VCO_FREQ) { - freq <<= 1; - st->r4_rf_div_sel++; + if (freq < ADF4350_MIN_VCO_FREQ) { + st->r4_rf_div_sel = fls_long(ADF4350_MIN_VCO_FREQ - 1) - fls_long(freq); + if ((freq << st->r4_rf_div_sel) < ADF4350_MIN_VCO_FREQ) + st->r4_rf_div_sel++; } + freq <<= st->r4_rf_div_sel; + if (freq > ADF4350_MAX_FREQ_45_PRESC) { prescaler = ADF4350_REG1_PRESCALER; mdiv = 75; -- 2.44.0