fail to disable MMU on ppc 8241

Benjamin Herrenschmidt benh at
Mon Apr 19 15:20:51 EST 2004

On Mon, 2004-04-19 at 13:55, llee wrote:
> Hi, there,
> I boot linux (2.6.3) on my ppc 8241 through vxworks bootloader. I'd got
> a port (on address 0x70020006) to constrol three LEDs, so I could know
> where the kernel going. But after the disable_mmu is called, I lost
> control to the LEDs, Any suggestion on this? As I know, vxworks use a
> one-to-one mapping MMU setup, I should must constrol the LEDs through
> the same address.

With mmu off, I suspect the 8241 acts as if the entire address space
was cacheable, which is a BAD THING for IOs typically.


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