[coreboot] Asus F2A85-M Pro: Accessing DMA1_RESET_REG in `isa_dma_init()` hangs system

[Paul Menzel]

Dear coreboot,

I am trying to finish the port for the Asus F2A85-M Pro (variant of Asus 
F2A85-M). After getting the serial console working [1], it can be seen, 
that accessing `DMA1_RESET_REG` in `isa_dma_init()` hangs the system [2].

outb(0, DMA1_RESET_REG);

Commenting this out, coreboot runs through and loads the payload. 
SeaBIOS has similar code, also hanging the system.

// first reset the DMA controllers
     outb(0, PORT_DMA1_MASTER_CLEAR);

I am at a loss. If you have an idea, how to fix it, I am all ears.

Kind regards,

Paul

[1]: https://review.coreboot.org/c/coreboot/+/39371/
[2]: https://review.coreboot.org/c/coreboot/+/39377/