From mboxrd@z Thu Jan 1 00:00:00 1970 From: linux@arm.linux.org.uk (Russell King - ARM Linux) Date: Wed, 11 Aug 2010 21:35:05 +0100 Subject: Problem with non aligned DMA in usbnet on ARM In-Reply-To: <4C62C7B3.2030706@nvidia.com> References: <4C627479.4060400@parrot.com> <4C62C7B3.2030706@nvidia.com> Message-ID: <20100811203505.GA463@n2100.arm.linux.org.uk> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Aug 11, 2010 at 08:54:27AM -0700, Gary King wrote: > On 08/11/2010 04:38 AM, Martin Fuzzey wrote: > > It seems to me these fixup functions are not intended to solve > > alignment issues but rather implement device specific framing (such as > > when the hardware packs multiple ethernet frames into a single urb) > > > I sent a patch to the list about 2 weeks ago that added support to > DMA bounce to bounce for misaligned buffers. We have a similar > problem with URB alignment for usbnet on Tegra's HCD: > > http://lists.arm.linux.org.uk/lurker/message/20100729.005746.b43fa1d9.en.html We don't want to add support for this to DMA bounce. DMA bounce is already a pain in the backside and causes its own set of problems - please let it die a long slow but quite death. If you want to see the kind of pain dmabounce causes, look at this long standing and as yet unsolved bug: http://bugzilla.kernel.org/show_bug.cgi?id=7760