From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753295AbbCJQh5 (ORCPT ); Tue, 10 Mar 2015 12:37:57 -0400 Received: from mail-la0-f41.google.com ([209.85.215.41]:41362 "EHLO mail-la0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753009AbbCJQhy (ORCPT ); Tue, 10 Mar 2015 12:37:54 -0400 From: "Grygorii.Strashko@linaro.org" X-Google-Original-From: "Grygorii.Strashko@linaro.org" Message-ID: <54FF1DDD.6060707@linaro.org> Date: Tue, 10 Mar 2015 18:37:49 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Russell King - ARM Linux , "Grygorii.Strashko@linaro.org" CC: Andrew Morton , Arnd Bergmann , Tejun Heo , Tony Lindgren , "linux-mm@kvack.org" , linux-arm , "linux-omap@vger.kernel.org" , Laura Abbott , open list , Santosh Shilimkar , Catalin Marinas , Peter Ujfalusi Subject: Re: ARM: OMPA4+: is it expected dma_coerce_mask_and_coherent(dev, DMA_BIT_MASK(64)); to fail? References: <54F8A68B.3080709@linaro.org> <20150305201753.GG29584@n2100.arm.linux.org.uk> <54FA2084.8050803@linaro.org> <20150310110538.GK29584@n2100.arm.linux.org.uk> In-Reply-To: <20150310110538.GK29584@n2100.arm.linux.org.uk> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Russell, On 03/10/2015 01:05 PM, Russell King - ARM Linux wrote: > On Fri, Mar 06, 2015 at 11:47:48PM +0200, Grygorii.Strashko@linaro.org wrote: >> On 03/05/2015 10:17 PM, Russell King - ARM Linux wrote: >>> On Thu, Mar 05, 2015 at 08:55:07PM +0200, Grygorii.Strashko@linaro.org wrote: >>>> The dma_coerce_mask_and_coherent() will fail in case 'Example 3' and succeed in cases 1,2. >>>> dma-mapping.c --> __dma_supported() >>>> if (sizeof(mask) != sizeof(dma_addr_t) && <== true for all OMAP4+ >>>> mask > (dma_addr_t)~0 && <== true for DMA_BIT_MASK(64) >>>> dma_to_pfn(dev, ~0) < max_pfn) { <== true only for Example 3 >>> >>> Hmm, I think this may make more sense to be "< max_pfn - 1" here, as >>> that would be better suited to our intention. >>> >>> The result of dma_to_pfn(dev, ~0) is the maximum PFN which we could >>> address via DMA, but we're comparing it with the maximum PFN in the >>> system plus 1 - so we need to subtract one from it. >> >> Ok. I'll try it. > > Any news on this - I think it is a real off-by-one bug which we should > fix in any case. Sorry for delay, there was a day-off on my side. As per my test results - with above change dma_coerce_mask_and_coherent(DMA_BIT_MASK(64)) and friends will succeed always. =========== Test results: ==== Test case 1: Input data: - RAM: start = 0x80000000 size = 0x80000000 - CONFIG_ARM_LPAE=n and sizeof(phys_addr_t) = 4 a) NO changes: memory registered within memblock as: memory.cnt = 0x1 memory[0x0] [0x00000080000000-0x000000fffffffe], 0x7fffffff bytes flags: 0x0 max_pfn = 0xFFFFF max_mapnr = 0x7FFFF dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)); -- succeeded b) with change in __dma_supported(): if (sizeof(mask) != sizeof(dma_addr_t) && mask > (dma_addr_t)~0 && - dma_to_pfn(dev, ~0) < max_pfn) { + dma_to_pfn(dev, ~0) < (max_pfn - 1)) { if (warn) { memory registered within memblock as: memory.cnt = 0x1 memory[0x0] [0x00000080000000-0x000000fffffffe], 0x7fffffff bytes flags: 0x0 max_pfn = 0xFFFFF max_mapnr = 0x7FFFF dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)); -- succeeded ==== Test case 2: Input data: - RAM: start = 0x80000000 size = 0x80000000 - CONFIG_ARM_LPAE=y and sizeof(phys_addr_t) = 8 a) NO changes: memory registered within memblock as: memory.cnt = 0x1 memory[0x0] [0x00000080000000-0x000000ffffffff], 0x80000000 bytes flags: 0x0 max_pfn = 0x100000 max_mapnr = 0x80000 dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)); -- failed [ 5.468470] asoc-simple-card sound@0: Coherent DMA mask 0xffffffffffffffff is larger than dma_addr_t allows [ 5.478706] asoc-simple-card sound@0: Driver did not use or check the return value from dma_set_coherent_mask()? [ 5.496620] davinci-mcasp 48468000.mcasp: ASoC: pcm constructor failed: -5 [ 5.503844] asoc-simple-card sound@0: ASoC: can't create pcm davinci-mcasp.0-tlv320aic3x-hifi :-5 b) with change in __dma_supported(): if (sizeof(mask) != sizeof(dma_addr_t) && mask > (dma_addr_t)~0 && - dma_to_pfn(dev, ~0) < max_pfn) { + dma_to_pfn(dev, ~0) < (max_pfn - 1)) { if (warn) { memory registered within memblock as: memory.cnt = 0x1 memory[0x0] [0x00000080000000-0x000000ffffffff], 0x80000000 bytes flags: 0x0 max_pfn = 0x100000 max_mapnr = 0x80000 dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)); -- succeeded regards, -grygorii -- regards, -grygorii