Mainline support for RP1_PWM / Pi 5 Cooling Fan

[DiJuMx]

Describe the bug

A few weeks ago, it came to my attention (here) that, although there is now mainline support for parts of the RP1 chip; some of the functionality is missing.
Specifically, the support for the PWM functions, which drive the cooling fan.

Steps to reproduce the behaviour

Either inspect the mainline kernel for the missing "pwm-rp1.c" source, and missing entries in the device trees.

Or, try the mainline kernel (6.18 or later), and observe no cooling fan operation.

Device (s)

Raspberry Pi 5

System

OS Version: Debian Forky / Testing / 14
Kernel Version: Linux rpi5-20260109 6.18.3+deb14-arm64 #1 SMP PREEMPT Debian 6.18.3-1 (2026-01-02) aarch64 GNU/Linux

Logs

No response

Additional context

No response

[pelwell]

The mainline kernel is missing lots of RP1 support - until very recently the upstream devs were insisting that the RP1 device tree must be applied as an overlay, which would have caused lots of problems. Now that we seem to have passed that hurdle the rest should go quicker, but it will still take a while and is not the highest priority task.