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Date: Mon, 27 Jan 2014 23:34:46 +0100 (CET) From: Guennadi Liakhovetski <g.liakhovetski@....de> To: Michal Simek <monstr@...str.eu> cc: Russell King - ARM Linux <linux@....linux.org.uk>, linux-kernel@...r.kernel.org, dmaengine@...r.kernel.org, linux-mmc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org Subject: Re: [Q] block / zynq: DMA bouncing Hi Michal, Russell, On Mon, 27 Jan 2014, Michal Simek wrote: > On 01/27/2014 06:52 PM, Russell King - ARM Linux wrote: > > On Mon, Jan 27, 2014 at 06:45:50PM +0100, Michal Simek wrote: > >> Why 0x4000? IRC Linux for ARM is using space for any purpose. > >> Russell knows this much better than I. > > > > Probably because as the kernel is loaded at 0x8000, it will place the > > swapper page table at 0x4000, thus covering from 0x4000 upwards. > > Ah yeah swapper. > > > > > Thus, the majority of your un-DMA-able memory will be kernel text or > > swapper page tables. > > Yes, exactly. > 0x0 - 0x4000 - reserving not to be used by DMA > 0x4000 - 0x8000 swapper page table > 0x8000 - 0x80000 kernel text + up Good, thanks for the explanations and examples, we'll do the same then! Thanks Guennadi --- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer http://www.open-technology.de/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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