5.4-stable review patch. If anyone has any objections, please let me know.
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From: Michael Hennerich michael.hennerich@analog.com
commit 33d7ecbf69aa7dd4145e3b77962bcb8759eede3d upstream.
The ADF4350/1 features a programmable dual-modulus prescaler of 4/5 or 8/9. When set to 4/5, the maximum RF frequency allowed is 3 GHz. Therefore, when operating the ADF4351 above 3 GHz, this must be set to 8/9. In this context not the RF output frequency is meant - it's the VCO frequency.
Therefore move the prescaler selection after we derived the VCO frequency from the desired RF output frequency.
This BUG may have caused PLL lock instabilities when operating the VCO at the very high range close to 4.4 GHz.
Fixes: e31166f0fd48 ("iio: frequency: New driver for Analog Devices ADF4350/ADF4351 Wideband Synthesizers") Signed-off-by: Michael Hennerich michael.hennerich@analog.com Signed-off-by: Nuno Sá nuno.sa@analog.com Reviewed-by: Andy Shevchenko andy@kernel.org Link: https://patch.msgid.link/20250829-adf4350-fix-v2-1-0bf543ba797d@analog.com Cc: Stable@vger.kernel.org Signed-off-by: Jonathan Cameron Jonathan.Cameron@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/iio/frequency/adf4350.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-)
--- a/drivers/iio/frequency/adf4350.c +++ b/drivers/iio/frequency/adf4350.c @@ -137,6 +137,19 @@ static int adf4350_set_freq(struct adf43 if (freq > ADF4350_MAX_OUT_FREQ || freq < st->min_out_freq) return -EINVAL;
+ 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_MAX_FREQ_45_PRESC) { prescaler = ADF4350_REG1_PRESCALER; mdiv = 75; @@ -145,13 +158,6 @@ static int adf4350_set_freq(struct adf43 mdiv = 23; }
- st->r4_rf_div_sel = 0; - - while (freq < ADF4350_MIN_VCO_FREQ) { - freq <<= 1; - st->r4_rf_div_sel++; - } - /* * Allow a predefined reference division factor * if not set, compute our own