From mboxrd@z Thu Jan 1 00:00:00 1970 From: filip.zyzniewski@gmail.com (Filip Zyzniewski) Date: Tue, 22 Dec 2009 17:33:30 +0100 Subject: DMA/cache problems on SA1110/SA1111 (Was: Re: USB Host on a SA1111) Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Dec 17, 2009 at 10:13 PM, Russell King - ARM Linux wrote: >> Russell you got any clues on this? From my point of view it really should >> just work. But Ive never done this myself. > > I've never really been that much involved with USB stuff, so can't really > comment. > There was some discussion about this at linux-usb mailing list. The interesting part is here: http://thread.gmane.org/gmane.linux.usb.general/25732 Especially the last post by Alan Stern: > I looked at one of these logs. ?Apparently there's a problem with the > memory caching and DMA. ?With some of the commands, the debugging > message shows incorrect data in the buffer. ?But later on, when the > data gets used, it obviously is correct. > This implies that something is wrong with the implementation of > dma_map_single() or dma_unmap_unsingle(). ?And it might explain why > changing the system's cache settings affects the behavior. I don't know architecture handling details, could somebody more knowledgeable give me some clues about where to begin fixing this? What could be broken? regards, Filip Zyzniewski