RP2040/RP2350 provide atomic bitmask set/clear aliases at +0x2000 and+0x3000 (RP2040 datasheet 2.1.2, p.18: https://datasheets.raspberrypi.com/rp2040/rp2040-datasheet.pdf), which modify only the selected bits. SIE_CTRL is also touched from the ISR, so this avoids the read-modify-write. Could we use those aliases here for PULLUP_EN?
#5563 (comment)
