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Wed, 4 Dec 2019 07:11:04 +0000 From: Jisheng Zhang To: Christoph Hellwig CC: Jun Nie , "ulf.hansson@linaro.org" , "robh+dt@kernel.org" , "mark.rutland@arm.com" , "adrian.hunter@intel.com" , "linux-mmc@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-block@vger.kernel.org" , "linux-ide@vger.kernel.org" Subject: Re: [PATCH 4/4] mmc: sdhci: Add DMA memory boundary workaround Thread-Topic: [PATCH 4/4] mmc: sdhci: Add DMA memory boundary workaround Thread-Index: AQHVqR6bSNy8xcyAyESfm+a1vx+I5KensdkAgAAQtICAAFjjgIAAB4wAgAAE9QCAADqtgIABKzyA Date: Wed, 4 Dec 2019 07:11:04 +0000 Message-ID: <20191204145709.34e42f56@xhacker.debian> References: <20191202144104.5069-1-jun.nie@linaro.org> <20191202144104.5069-5-jun.nie@linaro.org> <20191203103320.273a7309@xhacker.debian> <20191203165123.4e6f9e28@xhacker.debian> <20191203091824.GA4685@infradead.org> <20191203172434.39b2c2c2@xhacker.debian> <20191203130609.GA2144@infradead.org> In-Reply-To: <20191203130609.GA2144@infradead.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [124.74.246.114] x-clientproxiedby: TYAPR01CA0092.jpnprd01.prod.outlook.com (2603:1096:404:2c::32) To BYAPR03MB4773.namprd03.prod.outlook.com (2603:10b6:a03:139::21) authentication-results: spf=none (sender IP is ) smtp.mailfrom=Jisheng.Zhang@synaptics.com; 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received-spf: None (protection.outlook.com: synaptics.com does not designate permitted sender hosts) x-ms-exchange-senderadcheck: 1 x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: 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 x-ms-exchange-transport-forked: True Content-Type: text/plain; charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: synaptics.com X-MS-Exchange-CrossTenant-Network-Message-Id: e162b7c2-71dd-4716-09af-08d778892041 X-MS-Exchange-CrossTenant-originalarrivaltime: 04 Dec 2019 07:11:04.7208 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 335d1fbc-2124-4173-9863-17e7051a2a0e X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: 4uChLndwhnd1rnS2jyMw19g9LhW43/p84TMgBC+m80kYLBb9248nLrt7qujY2kv6RJIqp6N/o5Acfr3+aSStIA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR03MB3719 Sender: linux-mmc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mmc@vger.kernel.org Hi Christoph On Tue, 3 Dec 2019 05:06:09 -0800 Christoph Hellwig wrote: >=20 > On Tue, Dec 03, 2019 at 09:49:49AM +0000, Jisheng Zhang wrote: > > > As in exactly one boundary and not an alignment? Where the one > > > boundary is not a power of two and thus can't be expressed? =20 > > > > Take drivers/mmc/host/sdhci-of-dwcmshc.c for example, target physical D= MA addr > > can't span 128MB, 256MB, 128*3MB, ...128*nMB > > > > I'm not sure whether blk_queue_segment_boundary could solve this limita= tion. =20 >=20 > That is exaxtly the kind of limitation blk_queue_segment_boundary is > intended for. Until after dma_map_sg(), we can't know the physical DMA address range, so how does block layer know and check the DMA range beforehand? I'm a newbie = on block layer, could you please teach me? At the same time I'm reading the code as well. Thanks in advance