squealing belt/pulley and idling rpms increasing; 2017 XC90

[trimjimmy]

Hey, with my 2017 turbo supercharged xc90, today I noticed the engine light had come on. I had to drive quite a bit for work, and by the end of the day, when I parked in my carport, I heard a little squeal. I traced the squeal to the pulleys and belts on the right (passenger) side of the engine. That's all I know so far.
Also, when idling in park, the engine would slowly increase in rpm's to over 2000.
At first, it appeared like the computer was adjusting the idle: it would increase a little bit, and then hold, and the squeal would change nature. Then, a little higher. Sometimes coming down to around 1700 rpm, and then slowly going even higher. As the problem seemed progressive, I shut er down; didn't wait to see how high the rpms would eventually go.
Do those symptoms make enough sense to diagnose?
Luckily I have a 2008 V-8 that I can use for work tomorrow. There's a reasonable "high tech" shop in this little town I could take it to for diagnostic, but I am starting to lose trust in them. There's a very good Volvo Indie an hour away whom I would prefer to take it to, if I could drive that far with confidence of not causing irreparable damage.
I sent a shout out to Larry at Revolvo West with the same question.
What thinkest?
Jim

My Volvos: 2017 xc90; 2008 xc90 v-8; 2005 xc90 t-5 turbo (still at home, blown valve); 2006 xc70 (this and the rest are all gone); '96 850 wagon; '71 145 wagon; '70 145 wagon; 69 122 4-d; 68 122 2-d; 68 p1800

[Krons]

I’d change the belt and when you do it verify the idler bearings are ok. Hopefully a YouTube video is out there to help you DIY it.

[Oly850]

... Also chuck a new serpentine belt tensioner in there for good measure with a new belt. I think the ECU is hunting the idle to get the alternator to the correct RPM to run the car, charge the battery, heat your backside, etc. It also could be an alternator, but I'd probably do the previous items first.