Stefan Reinauer stepan@coresystems.de writes:
- yhlu yinghailu@gmail.com [060703 03:31]:
- use cpu cache for ohci or uhci buffer for packet.
Don't they circumvent the CPU to access the memory?
Depends on the cpu. As I recall Intel cpus flush data to memory for all of their cache coherence, so I don't think it would work there. I think AMD is some better in this regard, but I would be surprised if it worked. It makes sense to research it though.
So if we have to use DMA it looks like we are out of luck until after memory is initialized. Ouch!.
So sending some really simply usb commands out the EHCI debug port looks really interesting. If that works it is also very interesting for debugging kernels on modern hardware as well.
Eric