David Gibson wrote: > Well, I'm not sure I'd want to pollute the tree with this sort of > hack, but on the other hand it makes things work that wouldn't > otherwise. > > Does anyone think it's a good idea to commit the following patch: > > diff -urN /home/dgibson/kernel/linuxppc_2_4_devel/arch/ppc/mm/cachemap.c > linux-grinch/arch/ppc/mm/cachemap.c > --- /home/dgibson/kernel/linuxppc_2_4_devel/arch/ppc/mm/cachemap.c Thu Mar > 14 13:49:01 2002 > +++ linux-grinch/arch/ppc/mm/cachemap.c Wed Apr 3 11:51:30 2002 > @@ -137,7 +137,18 @@ > case PCI_DMA_NONE: > BUG(); > case PCI_DMA_FROMDEVICE: /* invalidate only */ > +#ifdef CONFIG_USB > + /* The USB stack is broken in that it uses DMA buffers > + on the stack which are on the stack and not > + cacheline aligned. That means cache invalidates > + before DMA transfers corrupt the stack on machines > + without DMA-consistent cache. This is a nasty > + workaround until the USB layer is fixed (apparently > + done in 2.5). */ > + flush_dcache_range(start, end); > +#else > invalidate_dcache_range(start, end); > +#endif > break; > case PCI_DMA_TODEVICE: /* writeback only */ > clean_dcache_range(start, end); > > > -- > David Gibson | For every complex problem there is a > david at gibson.dropbear.id.au | solution which is simple, neat and > | wrong. -- H.L. Mencken > http://www.ozlabs.org/people/dgibson > > > > >
Ah yes, We have done something simular (internally) and had the same reservations. This will help me with the ocp usb drivers i am working on. I would like to see some way of reminding us that this was done. let say a config option for 4xx_usb_dma_workarround. . -armin ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
