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Darwish" , stable@vger.kernel.org, Thomas Gleixner , Andy Shevchenko Content-Transfer-Encoding: base64 Content-Type: text/plain; charset="utf-8"; Format="flowed" Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" CgpBbSAxOS4wMi4yMSB1bSAxNjo1MyBzY2hyaWViIEFsYW4gU3Rlcm46Cj4gT24gRnJpLCBGZWIg MTksIDIwMjEgYXQgMDI6NDU6NTRQTSArMDEwMCwgQ2hyaXN0aWFuIEvDtm5pZyB3cm90ZToKPj4g V2VsbCBhcyBmYXIgYXMgSSBjYW4gc2VlIHRoaXMgaXMgYSByZWxhdGl2ZSBjbGVhciBOQUsuCj4+ Cj4+IFdoZW4gYSBkZXZpY2UgY2FuJ3QgZG8gRE1BIGFuZCBoYXMgbm8gRE1BIG1hc2sgdGhlbiB3 aHkgaXQgaXMgcmVxdWVzdGluZyBhbgo+PiBzZy10YWJsZSBpbiB0aGUgZmlyc3QgcGxhY2U/Cj4g VGhpcyBtYXkgbm90IGJlIGltcG9ydGFudCBmb3IgeW91ciBkaXNjdXNzaW9uLCBidXQgSSdkIGxp a2UgdG8gZ2l2ZSBhbgo+IGFuc3dlciB0byB0aGUgcXVlc3Rpb24gLS0gYXQgbGVhc3QsIGZvciB0 aGUgY2FzZSBvZiBVU0IuCj4KPiBBIFVTQiBkZXZpY2UgY2Fubm90IGRvIERNQSBhbmQgaGFzIG5v IERNQSBtYXNrLiAgTmV2ZXJ0aGVsZXNzLCBpZiB5b3UKPiB3YW50IHRvIHNlbmQgbGFyZ2UgYW1v dW50cyBvZiBidWxrIGRhdGEgdG8vZnJvbSBhIFVTQiBkZXZpY2UgdGhlbiB1c2luZwo+IGFuIFNH IHRhYmxlIGlzIG9mdGVuIGEgZ29vZCB3YXkgdG8gZG8gaXQuICBUaGUgcmVhc29uIGlzIHNpbXBs ZTogQWxsCj4gY29tbXVuaWNhdGlvbiB3aXRoIGEgVVNCIGRldmljZSBoYXMgdG8gZ28gdGhyb3Vn aCBhIFVTQiBob3N0IGNvbnRyb2xsZXIsCj4gYW5kIG1hbnkgKHRob3VnaCBub3QgYWxsKSBob3N0 IGNvbnRyb2xsZXJzIF9jYW5fIGRvIERNQSBhbmQgX2RvXyBoYXZlIGEKPiBETUEgbWFzay4KPgo+ IFRoZSBVU0IgbWFzcy1zdG9yYWdlIGFuZCB1YXMgZHJpdmVycyBpbiBwYXJ0aWN1bGFyIG1ha2Ug aGVhdnkgdXNlIG9mCj4gdGhpcyBtZWNoYW5pc20uCgpZZWFoLCBJIHdhcyBhc3N1bWluZyBzb21l dGhpbmcgbGlrZSB0aGF0IHdvdWxkIHdvcmsuCgpCdXQgaW4gdGhpcyBjYXNlIHRoZSBVU0IgZGV2 aWNlIHNob3VsZCBnaXZlIHRoZSBob3N0IGNvbnRyb2xsZXJzIGRldmljZSAKc3RydWN0dXJlIHRv IHRoZSBkbWFfYnVmX2F0dGFjaCBmdW5jdGlvbiBzbyB0aGF0IHRoZSBzZ190YWJsZSBjYW4gYmUg CmZpbGxlZCBpbiB3aXRoIERNQSBhZGRyZXNzZXMgcHJvcGVybHkuCgpSZWdhcmRzLApDaHJpc3Rp YW4uCgo+Cj4gQWxhbiBTdGVybgoKX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fX18KZHJpLWRldmVsIG1haWxpbmcgbGlzdApkcmktZGV2ZWxAbGlzdHMuZnJlZWRl c2t0b3Aub3JnCmh0dHBzOi8vbGlzdHMuZnJlZWRlc2t0b3Aub3JnL21haWxtYW4vbGlzdGluZm8v ZHJpLWRldmVsCg== 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=-7.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MSGID_FROM_MTA_HEADER,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 A2174C433E0 for ; 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dkim=none (message not signed) header.d=none;vger.kernel.org; dmarc=none action=none header.from=amd.com; Received: from MN2PR12MB3775.namprd12.prod.outlook.com (2603:10b6:208:159::19) by BL0PR12MB4930.namprd12.prod.outlook.com (2603:10b6:208:1c8::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3846.27; Fri, 19 Feb 2021 15:56:25 +0000 Received: from MN2PR12MB3775.namprd12.prod.outlook.com ([fe80::c1ff:dcf1:9536:a1f2]) by MN2PR12MB3775.namprd12.prod.outlook.com ([fe80::c1ff:dcf1:9536:a1f2%2]) with mapi id 15.20.3846.038; Fri, 19 Feb 2021 15:56:25 +0000 Subject: Re: [PATCH] drm/prime: Only call dma_map_sgtable() for devices with DMA support To: Alan Stern Cc: Thomas Zimmermann , daniel@ffwll.ch, airlied@linux.ie, maarten.lankhorst@linux.intel.com, mripard@kernel.org, sumit.semwal@linaro.org, gregkh@linuxfoundation.org, dri-devel@lists.freedesktop.org, noralf@tronnes.org, Christoph Hellwig , Johan Hovold , Andy Shevchenko , Sebastian Andrzej Siewior , "Ahmed S. Darwish" , Mathias Nyman , Oliver Neukum , Felipe Balbi , Thomas Gleixner , stable@vger.kernel.org References: <20210219134014.7775-1-tzimmermann@suse.de> <02a45c11-fc73-1e5a-3839-30b080950af8@amd.com> <20210219155328.GA1111829@rowland.harvard.edu> From: =?UTF-8?Q?Christian_K=c3=b6nig?= Message-ID: Date: Fri, 19 Feb 2021 16:56:16 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 In-Reply-To: <20210219155328.GA1111829@rowland.harvard.edu> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [2a02:908:1252:fb60:eb81:6e66:649f:1820] X-ClientProxiedBy: AM3PR04CA0139.eurprd04.prod.outlook.com (2603:10a6:207::23) To MN2PR12MB3775.namprd12.prod.outlook.com (2603:10b6:208:159::19) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [IPv6:2a02:908:1252:fb60:eb81:6e66:649f:1820] (2a02:908:1252:fb60:eb81:6e66:649f:1820) by AM3PR04CA0139.eurprd04.prod.outlook.com (2603:10a6:207::23) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3868.27 via Frontend Transport; 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Nevertheless, if you > want to send large amounts of bulk data to/from a USB device then using > an SG table is often a good way to do it. The reason is simple: All > communication with a USB device has to go through a USB host controller, > and many (though not all) host controllers _can_ do DMA and _do_ have a > DMA mask. > > The USB mass-storage and uas drivers in particular make heavy use of > this mechanism. Yeah, I was assuming something like that would work. But in this case the USB device should give the host controllers device structure to the dma_buf_attach function so that the sg_table can be filled in with DMA addresses properly. Regards, Christian. > > Alan Stern