[PATCH v14 7/7] riscv: dts: thead: Add PWM fan and thermal control

[Michal Wilczynski]

On 8/22/25 22:49, Drew Fustini wrote:
> On Wed, Aug 20, 2025 at 10:35:42AM +0200, Michal Wilczynski wrote:
>> Add Device Tree nodes to enable a PWM controlled fan and it's associated
>> thermal management for the Lichee Pi 4A board.
>>
>> This enables temperature-controlled active cooling for the Lichee Pi 4A
>> board based on SoC temperature.
>>
>> Reviewed-by: Drew Fustini <fustini at kernel.org>
>> Tested-by: Drew Fustini <fustini at kernel.org>
>> Signed-off-by: Michal Wilczynski <m.wilczynski at samsung.com>
>> ---
>>  arch/riscv/boot/dts/thead/th1520-lichee-pi-4a.dts | 67 +++++++++++++++++++++++
>>  1 file changed, 67 insertions(+)
> 
> Do you think it makes sense to coordinate this with the "Initial thermal
> management for Lichee Pi 4A board" series [1] from Icenowy?

Hi,
It seems to me like using the HW PWM is just a better solution for
driving the fans. However as pointed in the discussion currently Rust
requires LLVM, so people compiling with gcc will not be able to compile
the driver for some time until the gcc support becomes better.

I think there is a way to express in Device Tree the fallback logic -
if Rust not available then use SW PWM. So I guess the pragmatic way to
go is to merge SW PWM temporary fix first, and later when gcc becomes
better at compiling Rust patch it up to use HW PWM instead.

> 
> Thanks,
> Drew
> 
> [1] https://lore.kernel.org/linux-riscv/20250816093209.2600355-1-uwu@icenowy.me/
> 

Best regards,
-- 
Michal Wilczynski <m.wilczynski at samsung.com>