On Tue, Jan 17, 2006 at 11:40:53AM +0200, Riisisulg wrote:
> Hello. I'm using AMD Alchemy db1550 with au1550, it has 2.6.15 kernel
> patched with linux-2.6.14.5-mips-1.patch, i have compiled cross compiler
> for the platform (but not checked it for correctness)
>
> since db1550 does not have USB2.0 but instead has two PCI slots, i
> installed NEC's PCI to USB 2.0 host controller board to it. I was able
> to load ehci-hcd driver with success but after the usb mass storage
> device was inserted the system hanged.
> After debugging a while i found out that function atomic_add did not
> return. I run few tests where atomic add asm code was alerted and got
> confidence that sc instruction did not never succeed so the cycle was
> repeating forever.
The operation of ll/sc is undefined on uncached memory; non-coherent
MIPS systems - that is most embedded MIPS systems - will return non
cache-coherent memory for dma_alloc_coherent. Yes, the naming sucks,
dma_alloc_{non}coherent do the opposite of what their name is.
Ralf
