Issue in TDD mode select with adi,tdd-skip-vco-cal-enable set.

We use the IIO driver to setup AD9361 on E310 to work in TDD 1rx-1tx mode. Since we are still in exploring phase, so we are still using SPI to choose between TX and RX state. It seems to be working.According to https://wiki.analog.com/resources/tools-software/linux-drivers/iio-transceiver/ad9361, the IIO driver supports direct transition from TX to RX or vice versa without the need to spell out the intermediate "alert " state.

Next, we hope to skip the VCO calibration since our application has a very tighten window for that. Therefore, we also enabled "adi,tdd-skip-vco-cal-enable". However, after this configuration, we could no longer enable the tx mode. It is still possible to switch to rx mode, but whenever we try to write "tx" into the channel attribute 'ensm_mode', it stuck at the alert mode. See the following.

root@usrp-e310-linux:/sys/kernel/debug/iio/iio:device0# cat adi,frequency-division-duplex-mode-enable 

0

root@usrp-e310-linux:/sys/kernel/debug/iio/iio:device0# cat adi,tdd-skip-vco-cal-enable 

1

root@usrp-e310-linux:/sys/bus/iio/devices/iio:device0# echo rx > ensm_mode

root@usrp-e310-linux:/sys/bus/iio/devices/iio:device0# cat ensm_mode

rx

root@usrp-e310-linux:/sys/bus/iio/devices/iio:device0# echo tx > ensm_mode

root@usrp-e310-linux:/sys/bus/iio/devices/iio:device0# cat ensm_mode

alert

(Question 1) What steps or issues did we miss to cause the above issue with adi,tdd-skip-vco-cal-enable is set?

(Question 2) Related with the first question, was the debug attribute adi,tdd-use-fdd-vco-tables-enable eliminated? If so, is it automatically chosen when TDD VCO calibration is disabled?

The attribute adi,tdd-use-fdd-vco-tables-enable is on page https://wiki.analog.com/resources/tools-software/linux-drivers/iio-transceiver/ad9361-customization, but we couldn't find it in the device tree in :/sys/kernel/debug/iio/iio:device0, see the following.

root@usrp-e310-linux:/sys/kernel/debug/iio/iio:device0# ls adi,tdd*

adi,tdd-skip-vco-cal-enable         adi,tdd-use-dual-synth-mode-enable



Added additional information and spell out the questions.
[edited by: c3commsystems at 2:52 PM (GMT -4) on 26 Oct 2020]

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