Wow, that was quick: Thanks to Lucas Stach our #etnaviv runtime power managemt fix already landed in linux-next: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/log/?qt=range&q=ea4ed4a55f7363ad8db1863bd536548fb7e5c6aa..78f2bfa3181cd7ee134274aa17177dd933c69dc1

The fix hits the #librem5 with the next kernel update.