[Q] block / zynq: DMA bouncing
From: monstr@monstr.eu (Michal Simek)
Date: 2014-01-27 17:57:56
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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: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.
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 Thanks, Michal -- Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91 w: www.monstr.eu p: +42-0-721842854 Maintainer of Linux kernel - Microblaze cpu - http://www.monstr.eu/fdt/ Maintainer of Linux kernel - Xilinx Zynq ARM architecture Microblaze U-BOOT custodian and responsible for u-boot arm zynq platform -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 263 bytes Desc: OpenPGP digital signature URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20140127/f6b2b00c/attachment.sig>