CPU Cache and busdma usage in USB
raj at semihalf.com
Wed Jul 8 09:14:27 UTC 2009
On 2009-07-07, at 18:46, Hans Petter Selasky wrote:
>> I had Checked USB behaviour on PowerPC without hardware cache
>> The problem also exists here and patch helps.
> In my source code view the busdma sync function is empty for power-
> pc. Your
> patch should have no effect at all for sync operations?
This was about the PPC4xx PowerPC port, not committed to the tree yet.
Unlike most PowerPC this system has a de-coherent DMA and therefore
its busdma sync is non empty, but needs to enforce coherency by
The point is this is another platform on which USB stack (usb_pc_cpu_*
functions) shows similar issues as reported for ARM and MIPS.
More information about the freebsd-usb