From mboxrd@z Thu Jan 1 00:00:00 1970 From: brian@walsh.ws (Brian Walsh) Date: Tue, 29 Sep 2009 11:16:02 -0400 Subject: ixp4xx dmabounce In-Reply-To: <20090927165531.GC20093@n2100.arm.linux.org.uk> References: <20090917215302.GA14939@n2100.arm.linux.org.uk> <20090927165531.GC20093@n2100.arm.linux.org.uk> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Sun, Sep 27, 2009 at 12:55 PM, Russell King - ARM Linux wrote: > On Tue, Sep 22, 2009 at 06:02:19PM -0400, Brian Walsh wrote: >> On Thu, Sep 17, 2009 at 5:53 PM, Russell King - ARM Linux >> wrote: >> > >> > On Thu, Sep 17, 2009 at 05:02:59PM -0400, Brian Walsh wrote: >> > > Any ideas or suggestions? >> > >> > It's caused because we don't allow dma_free_coherent() to be called from >> > IRQ context (which is reasonable because it needs to flush TLBs across >> > all processors on SMP systems.) >> >> I am not running on an SMP system so would this even be a problem? > > Yes - because it's there to ensure that the API is used in a consistent > way. Right, I was just referring to it being a problem in my specific situation not in the general case. > >> > Unfortunately, with the DMA bounce code enabled, this function does get >> > called from IRQ context, and so tends to spit out these warnings. >> > >> > I did have a patch which made dma_free_coherent() lazy, but it was >> > reported that the suffered disk corruption (though it was never >> > conclusive whether it was caused by the patch or not.) ?Here's an >> > updated version of that patch. >> > >> >> I did not see any data rate improvement using this patch over just commenting >> out the warning stack dump.? I am still seeing about half the data transfer rate >> using the high speed ehci USB controller over the full speed ohci USB >> controller. > > I didn't suggest it would improve the data rate - only that it should > fix the stack dump. > > I'd really like to get this patch properly tested and confirmed that it > does _not_ actually cause corruption, so that I can get it merged. > I will be able to help you test this patch once I get past this issue I am dealing with.