From: Michal Simek <monstr@monstr.eu>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de>,
linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org,
linux-mmc@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [Q] block / zynq: DMA bouncing
Date: Mon, 27 Jan 2014 18:57:50 +0100 [thread overview]
Message-ID: <52E69E1E.3020202@monstr.eu> (raw)
In-Reply-To: <20140127175231.GU15937@n2100.arm.linux.org.uk>
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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:
>> 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
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WARNING: multiple messages have this Message-ID (diff)
From: monstr@monstr.eu (Michal Simek)
To: linux-arm-kernel@lists.infradead.org
Subject: [Q] block / zynq: DMA bouncing
Date: Mon, 27 Jan 2014 18:57:50 +0100 [thread overview]
Message-ID: <52E69E1E.3020202@monstr.eu> (raw)
In-Reply-To: <20140127175231.GU15937@n2100.arm.linux.org.uk>
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
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
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next prev parent reply other threads:[~2014-01-27 17:57 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-27 15:13 [Q] block / zynq: DMA bouncing Guennadi Liakhovetski
2014-01-27 15:13 ` Guennadi Liakhovetski
2014-01-27 15:24 ` Ben Dooks
2014-01-27 15:24 ` Ben Dooks
2014-01-27 15:24 ` Ben Dooks
2014-01-27 15:35 ` Guennadi Liakhovetski
2014-01-27 15:35 ` Guennadi Liakhovetski
2014-01-27 17:02 ` Russell King - ARM Linux
2014-01-27 17:02 ` Russell King - ARM Linux
2014-01-27 17:45 ` Michal Simek
2014-01-27 17:45 ` Michal Simek
2014-01-27 17:52 ` Russell King - ARM Linux
2014-01-27 17:52 ` Russell King - ARM Linux
2014-01-27 17:57 ` Michal Simek [this message]
2014-01-27 17:57 ` Michal Simek
2014-01-27 22:34 ` Guennadi Liakhovetski
2014-01-27 22:34 ` Guennadi Liakhovetski
2014-01-28 13:28 ` Guennadi Liakhovetski
2014-01-28 13:33 ` Guennadi Liakhovetski
2014-01-28 13:48 ` Russell King - ARM Linux
2014-01-28 13:54 ` Michal Simek
2014-01-28 18:34 ` Jason Gunthorpe
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