Messages in this thread | | | Date | Tue, 16 Feb 2010 10:44:26 -0500 (EST) | From | Alan Stern <> | Subject | RE: USB mass storage and ARM cache coherency |
| |
On Tue, 16 Feb 2010, Shilimkar, Santosh wrote:
> > Your original patch however kills ehci, ohci and uhci on some architectures. > Well the patch was making _ONLY_ control transfers use PIO and rest of > the transfer would still use dma. So not sure how much performance impact would > be because of that. > Another issue with that patch is there are few controllers which can't do PIO > at all and hence the patch would broke those controllers.
More than "a few"! None of the EHCI, OHCI, or UHCI controllers used in Intel-compatible desktop and laptop systems can do PIO. That's what Oliver meant.
Alan Stern
| |