[Q] block / zynq: DMA bouncing
From: Guennadi Liakhovetski <hidden>
Date: 2014-01-27 22:34:58
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linux-mmc, lkml
Hi Michal, Russell, On Mon, 27 Jan 2014, Michal Simek wrote:
On 01/27/2014 06:52 PM, Russell King - ARM Linux wrote:quoted
On Mon, Jan 27, 2014 at 06:45:50PM +0100, Michal Simek wrote:quoted
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.quoted
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/