From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752381AbaFYA0H (ORCPT ); Tue, 24 Jun 2014 20:26:07 -0400 Received: from mail-ie0-f172.google.com ([209.85.223.172]:64629 "EHLO mail-ie0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751211AbaFYA0F (ORCPT ); Tue, 24 Jun 2014 20:26:05 -0400 Date: Tue, 24 Jun 2014 17:26:02 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Mark Salter cc: Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] arm64: fix CONFIG_ZONE_DMA on systems with no 32-bit addressable DRAM In-Reply-To: <1403499940-11258-1-git-send-email-msalter@redhat.com> Message-ID: References: <1403499940-11258-1-git-send-email-msalter@redhat.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 23 Jun 2014, Mark Salter wrote: > Commit 2d5a5612bc (arm64: Limit the CMA buffer to 32-bit if ZONE_DMA) > forces the CMA buffer to be 32-bit addressable if CONFIG_ZONE_DMA is > defined. This breaks CMA on platforms with no 32-bit addressable DRAM. > This patch checks to make sure there is 32-bit addressable DRAM before > setting the 32-bit limit. If there is none, no limit is placed on the > CMA buffer. This allows a single kernel (with CONFIG_ZONE_DMA defined) > to support platforms requiring the 32-bit limit and platforms with no > 32-bit limit. > > Signed-off-by: Mark Salter > --- > arch/arm64/mm/init.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > index c5415e2..2925576 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -149,8 +149,17 @@ void __init arm64_memblock_init(void) > early_init_fdt_scan_reserved_mem(); > > /* 4GB maximum for 32-bit only capable devices */ > - if (IS_ENABLED(CONFIG_ZONE_DMA)) > + if (IS_ENABLED(CONFIG_ZONE_DMA)) { > dma_phys_limit = dma_to_phys(NULL, DMA_BIT_MASK(32)) + 1; > + /* > + * If platform doesn't have DRAM within the dma_phys_limit, > + * remove the limit altogether. This allows one kernel (with > + * CONFIG_ZONE_DMA defined) to support platforms with 32-bit > + * only devices and platforms with no 32-bit DRAM. > + */ > + if (dma_phys_limit <= memblock_start_of_DRAM()) > + dma_phys_limit = 0; > + } > dma_contiguous_reserve(dma_phys_limit); > > memblock_allow_resize(); It is a shame that we have very similar logic, all dependent on memblock_start_of_DRAM(), in both zone_sizes_init() and arm64_memblock_init() and the latter having to be called before the former. I assume there's no way to make this cleaner in the bootstrap code so the dma_to_phys(NULL, DMA_BIT_MASK(32)) + 1 limit can be handled properly in a single location?