Diddy is doing OK in the slammer ... at least according to his son.

TMZ just got King Combs out in L.A. ... and he told us the disgraced music mogul was holding up just fine at Federal Correctional Institution Fort Dix in New Jersey -- and KC thanked fans for their support.

See for yourself ... we chopped it up with Diddy's son -- ironically with a police siren in the background -- and he made it clear ... he thinks it's time to "free pops."

It was a short conversation ... but enough to see King was relaxed and chill with the questions -- and seemed super genuine in his responses.

As you know ... Diddy is currently locked up after being convicted of two felony counts of transporting individuals across state lines to engage in prostitution.

On April 9, Diddy's lawyers appeared before a federal appeals court and argued his freak-offs were not a violation of any law and that his 50-month sentence was way out of line. The judges are still in their decision-making process, and as of today, he is currently scheduled to be released on April 15, 2028.