Here you can not connect the RTC SQW to the RTC_XTALI , for the RTC_XTALI is the analog clock input.
CKIL (Clock Input Low) is a dedicated pin used to receive external 32.768 kHz digital clock signals, so you need to connect the RTC SQW to the CKIL on the i.MX6Q side. You need to follow the circuilt recommend.
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