From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Simek Subject: Re: [Q] block / zynq: DMA bouncing Date: Mon, 27 Jan 2014 18:57:50 +0100 Message-ID: <52E69E1E.3020202@monstr.eu> References: <20140127170230.GQ15937@n2100.arm.linux.org.uk> <52E69B4E.5010604@monstr.eu> <20140127175231.GU15937@n2100.arm.linux.org.uk> Reply-To: monstr@monstr.eu Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="uFFiXq1NItkHisFCj743jDDeUTD4WRL1R" Return-path: Received: from mail-ee0-f46.google.com ([74.125.83.46]:47180 "EHLO mail-ee0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753804AbaA0R5y (ORCPT ); Mon, 27 Jan 2014 12:57:54 -0500 Received: by mail-ee0-f46.google.com with SMTP id c13so2411035eek.19 for ; Mon, 27 Jan 2014 09:57:53 -0800 (PST) In-Reply-To: <20140127175231.GU15937@n2100.arm.linux.org.uk> Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Russell King - ARM Linux Cc: Guennadi Liakhovetski , linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org, linux-mmc@vger.kernel.org, linux-arm-kernel@lists.infradead.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --uFFiXq1NItkHisFCj743jDDeUTD4WRL1R Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable 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. >=20 > 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. >=20 > 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 --=20 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 --uFFiXq1NItkHisFCj743jDDeUTD4WRL1R Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iEYEARECAAYFAlLmnh8ACgkQykllyylKDCHf0gCeLPB3O2+U+u37SyE1sIAVO4np WpkAn1VPgiAYBbDuJClZRZKL901DDQ15 =MZGi -----END PGP SIGNATURE----- --uFFiXq1NItkHisFCj743jDDeUTD4WRL1R-- From mboxrd@z Thu Jan 1 00:00:00 1970 From: monstr@monstr.eu (Michal Simek) Date: Mon, 27 Jan 2014 18:57:50 +0100 Subject: [Q] block / zynq: DMA bouncing In-Reply-To: <20140127175231.GU15937@n2100.arm.linux.org.uk> References: <20140127170230.GQ15937@n2100.arm.linux.org.uk> <52E69B4E.5010604@monstr.eu> <20140127175231.GU15937@n2100.arm.linux.org.uk> Message-ID: <52E69E1E.3020202@monstr.eu> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 263 bytes Desc: OpenPGP digital signature URL: