From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 478ADC47082 for ; Tue, 8 Jun 2021 16:11:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2E2B461027 for ; Tue, 8 Jun 2021 16:11:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232901AbhFHQNf (ORCPT ); Tue, 8 Jun 2021 12:13:35 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.85.151]:37271 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232131AbhFHQNL (ORCPT ); Tue, 8 Jun 2021 12:13:11 -0400 Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-234-62pR9OyRO-SSSIbw5JosqQ-1; Tue, 08 Jun 2021 17:11:16 +0100 X-MC-Unique: 62pR9OyRO-SSSIbw5JosqQ-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.18; Tue, 8 Jun 2021 17:11:15 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.018; Tue, 8 Jun 2021 17:11:15 +0100 From: David Laight To: 'Christoph Hellwig' CC: Guo Ren , Nick Kossifidis , "Drew Fustini" , Anup Patel , "Palmer Dabbelt" , "wefu@redhat.com" , =?utf-8?B?V2VpIFd1ICjlkLTkvJ8p?= , linux-riscv , Linux Kernel Mailing List , linux-arch , "linux-sunxi@lists.linux.dev" , Guo Ren , Paul Walmsley , Benjamin Koch , Matteo Croce , Wei Fu Subject: RE: [PATCH RFC 0/3] riscv: Add DMA_COHERENT support Thread-Topic: [PATCH RFC 0/3] riscv: Add DMA_COHERENT support Thread-Index: AQHXW2Yf+E+HbgFRkkm3Xv2DTkp7y6sKNaKQ///5qoCAABnpEA== Date: Tue, 8 Jun 2021 16:11:15 +0000 Message-ID: <7a11939f4c7f4494a7d86b8d5f1bb702@AcuMS.aculab.com> References: <20210519064435.GA3076809@x1> <20210519065352.GA31590@lst.de> <29733b0931d9dd6a2f0b6919067c7efe@mailhost.ics.forth.gr> <20210607062701.GB24060@lst.de> <2db975b5f24149b19191120b9f0f506b@AcuMS.aculab.com> <20210608153203.GA6802@lst.de> In-Reply-To: <20210608153203.GA6802@lst.de> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: base64 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org RnJvbTogJ0NocmlzdG9waCBIZWxsd2lnJw0KPiBTZW50OiAwOCBKdW5lIDIwMjEgMTY6MzINCj4g DQo+IE9uIFR1ZSwgSnVuIDA4LCAyMDIxIGF0IDAzOjAwOjE3UE0gKzAwMDAsIERhdmlkIExhaWdo dCB3cm90ZToNCj4gPiBJdCBpcyBhbG1vc3QgaW1wb3NzaWJsZSB0byBpbnRlcmZhY2UgdG8gbWFu eSBldGhlcm5ldCBjaGlwcyB3aXRob3V0DQo+ID4gZWl0aGVyIGNvaGVyZW50IG9yIHVuY2FjaGVk IG1lbW9yeSBmb3IgdGhlIGRlc2NyaXB0b3IgcmluZ3MuDQo+ID4gVGhlIHN0YXR1cyBiaXRzIG9u IHRoZSB0cmFuc21pdCByaW5nIGFyZSBwYXJ0aWN1bGFybHkgcHJvYmxlbWF0aWMuDQo+ID4NCj4g PiBUaGUgcmVjZWl2ZSByaW5nIGNhbiBiZSBkb25lIHdpdGggd3JpdGViYWNrK2ludmFsaWRhdGUg cHJvdmlkZWQgeW91DQo+ID4gZmlsbCBhIGNhY2hlIGxpbmUgYXQgYSB0aW1lLg0KPiANCj4gSXQg aXMgaG9ycmlibGUsIGJ1dCBpdCBoYXMgYmVlbiBkb25lLiAgVGFrZSBhIGxvb2sgYXQ6DQo+IA0K PiBkcml2ZXJzL25ldC9ldGhlcm5ldC9pODI1eHgvbGFzaV84MjU5Ni5jIGFuZA0KPiBkcml2ZXJz L25ldC9ldGhlcm5ldC9zZWVxL3NnaXNlZXEuYw0KDQpJIGd1ZXNzIHRoYXQgZWFjaCB0cmFuc21p dCBoYXMgdG8gYmUgc3BsaXQgaW50byBlbm91Z2gNCmZyYWdtZW50cyB0aGF0IHRoZXkgZmlsbCBh IGNhY2hlIGxpbmUuDQpUaGF0IHdvbid0IHdvcmsgd2l0aCBzb21lIChwcm9iYWJseSBvbGQgbm93 KSBkZXZpY2VzIHRoYXQNCnJlcXVpcmUgdGhlIGZpcnN0IGZyYWdtZW50IHRvIGJlIDY0IGJ5dGVz IGJlY2F1c2UgaXQgd29uJ3QNCmJhY2stdXAgdGhlIGRlc2NyaXB0b3JzIGFmdGVyIGEgY29sbGlz aW9uLg0KDQpJdCdzIGFsbCBhcyBob3JyaWQgYXMgYSBEU1Agd2UgaGF2ZSB0aGF0IGNhbid0IHJl Y2VpdmUgZXRoZXJuZXQNCmZyYW1lcyBvbnRvIGEgNG4rMiBib3VuZGFyeSBhbmQgZG9lc24ndCBz dXBwb3J0IG1pc2FsaWduZWQgYWNjZXNzZXMuDQoNCk1pbmQgeW91LCBTdW4ncyBvcmlnaW5hbCBT YnVzIGV0aGVybmV0IGJvYXJkIGhhZCB0byBiZSBnaXZlbg0KYSA0biBhbGlnbmVkIHJ4IGJ1ZmZl ciBhbmQgdGhlbiBhIG1pc2FsaWduZWQgY29weSBkb25lIGluIGtlcm5lbA0KaW4gb3JkZXIgdG8g bm90IGRyb3AgcGFja2V0cyENCg0KCURhdmlkDQoNCi0NClJlZ2lzdGVyZWQgQWRkcmVzcyBMYWtl c2lkZSwgQnJhbWxleSBSb2FkLCBNb3VudCBGYXJtLCBNaWx0b24gS2V5bmVzLCBNSzEgMVBULCBV Sw0KUmVnaXN0cmF0aW9uIE5vOiAxMzk3Mzg2IChXYWxlcykNCg== From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 13702C47082 for ; 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Tue, 8 Jun 2021 17:11:15 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.018; Tue, 8 Jun 2021 17:11:15 +0100 From: David Laight To: 'Christoph Hellwig' CC: Guo Ren , Nick Kossifidis , "Drew Fustini" , Anup Patel , "Palmer Dabbelt" , "wefu@redhat.com" , =?utf-8?B?V2VpIFd1ICjlkLTkvJ8p?= , linux-riscv , Linux Kernel Mailing List , linux-arch , "linux-sunxi@lists.linux.dev" , Guo Ren , Paul Walmsley , Benjamin Koch , Matteo Croce , Wei Fu Subject: RE: [PATCH RFC 0/3] riscv: Add DMA_COHERENT support Thread-Topic: [PATCH RFC 0/3] riscv: Add DMA_COHERENT support Thread-Index: AQHXW2Yf+E+HbgFRkkm3Xv2DTkp7y6sKNaKQ///5qoCAABnpEA== Date: Tue, 8 Jun 2021 16:11:15 +0000 Message-ID: <7a11939f4c7f4494a7d86b8d5f1bb702@AcuMS.aculab.com> References: <20210519064435.GA3076809@x1> <20210519065352.GA31590@lst.de> <29733b0931d9dd6a2f0b6919067c7efe@mailhost.ics.forth.gr> <20210607062701.GB24060@lst.de> <2db975b5f24149b19191120b9f0f506b@AcuMS.aculab.com> <20210608153203.GA6802@lst.de> In-Reply-To: <20210608153203.GA6802@lst.de> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210608_091122_603264_8681D9E0 X-CRM114-Status: GOOD ( 14.45 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org From: 'Christoph Hellwig' > Sent: 08 June 2021 16:32 > > On Tue, Jun 08, 2021 at 03:00:17PM +0000, David Laight wrote: > > It is almost impossible to interface to many ethernet chips without > > either coherent or uncached memory for the descriptor rings. > > The status bits on the transmit ring are particularly problematic. > > > > The receive ring can be done with writeback+invalidate provided you > > fill a cache line at a time. > > It is horrible, but it has been done. Take a look at: > > drivers/net/ethernet/i825xx/lasi_82596.c and > drivers/net/ethernet/seeq/sgiseeq.c I guess that each transmit has to be split into enough fragments that they fill a cache line. That won't work with some (probably old now) devices that require the first fragment to be 64 bytes because it won't back-up the descriptors after a collision. It's all as horrid as a DSP we have that can't receive ethernet frames onto a 4n+2 boundary and doesn't support misaligned accesses. Mind you, Sun's original Sbus ethernet board had to be given a 4n aligned rx buffer and then a misaligned copy done in kernel in order to not drop packets! David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales) _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv