From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ducie-dc1.codethink.co.uk ([185.25.241.215]:37081 "EHLO ducie-dc1.codethink.co.uk" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1758459AbaCTPg6 (ORCPT ); Thu, 20 Mar 2014 11:36:58 -0400 Message-ID: <532B0B14.7040600@codethink.co.uk> Date: Thu, 20 Mar 2014 16:36:52 +0100 From: Ben Dooks MIME-Version: 1.0 To: Russell King - ARM Linux CC: Arnd Bergmann , linux-sh@vger.kernel.org, "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Magnus Damm , Ben Dooks , Bjorn Helgaas , Simon Horman , linux-arm-kernel@lists.infradead.org Subject: Re: DMABOUNCE in pci-rcar References: <201402241200.21944.arnd@arndb.de> <5165962.7bqj51B15Z@wuerfel> <532B0384.1000400@codethink.co.uk> <20140320152640.GW7528@n2100.arm.linux.org.uk> In-Reply-To: <20140320152640.GW7528@n2100.arm.linux.org.uk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-pci-owner@vger.kernel.org List-ID: On 20/03/14 16:26, Russell King - ARM Linux wrote: > On Thu, Mar 20, 2014 at 04:04:36PM +0100, Ben Dooks wrote: >> On 26/02/14 20:57, Arnd Bergmann wrote: >>> On Wednesday 26 February 2014 12:48:17 Bjorn Helgaas wrote: >>>> On Mon, Feb 24, 2014 at 4:00 AM, Arnd Bergmann wrote: >>>>> Hi Magnus, >>>>> >>>>> I noticed during randconfig testing that you enabled DMABOUNCE for the >>>>> pci-rcar-gen2 driver as posted in this patch https://lkml.org/lkml/2014/2/5/30 >>>>> >>>>> I didn't see the original post unfortunately, but I fear we have to >>>>> revert it and come up with a better solution, ... >>>> >>>> Sounds like I should drop the following patches from my pci/host-rcar >>>> branch for now? >>>> >>>> PCI: rcar: Add DMABOUNCE support >>>> PCI: rcar: Enable BOUNCE in case of HIGHMEM >>>> PCI: rcar: Make the Kconfig dependencies more generic >>> >>> Sounds good to me. The last patch is actually fine, but you'll have to >>> fix the context to apply it without the other two. >> >> As a note, if we now boot a Lager with DT on 3.14-rc3 series the USB >> controllers no longer work with full 2GiB RAM enabled in the device >> tree. >> >> Could we work around this by having 1GiB of memory defined in the >> 32bit memory and then add the rest of the 3GiB from the >32bit >> area via LPAE? Will the kernel ever try to allocate DMA memory from >> anything >32bit? > > Ignore highmem. What is the actual hardware restriction concerning memory > it can access? If the window is set to 2GiB it can only access 2GiB aligned to 2GiB boundary, however DRAM spans a 2GiB boundary (being at 1-3GiB) -- Ben Dooks http://www.codethink.co.uk/ Senior Engineer Codethink - Providing Genius