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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham 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 8B032C43381 for ; Wed, 20 Feb 2019 09:30:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 621572070B for ; Wed, 20 Feb 2019 09:30:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727027AbfBTJag (ORCPT ); Wed, 20 Feb 2019 04:30:36 -0500 Received: from mga11.intel.com ([192.55.52.93]:11074 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725832AbfBTJaf (ORCPT ); Wed, 20 Feb 2019 04:30:35 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 20 Feb 2019 01:30:34 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,390,1544515200"; d="asc'?scan'208";a="145749931" Received: from pipin.fi.intel.com (HELO localhost) ([10.237.72.175]) by fmsmga004.fm.intel.com with ESMTP; 20 Feb 2019 01:30:32 -0800 From: Felipe Balbi To: Nicolas Saenz Julienne , Mathias Nyman Cc: oneukum@suse.com, Nicolas Saenz Julienne , Greg Kroah-Hartman , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] usb: xhci: add Immediate Data Transfer support In-Reply-To: <20190219162945.22889-1-nsaenzjulienne@suse.de> References: <20190219162945.22889-1-nsaenzjulienne@suse.de> Date: Wed, 20 Feb 2019 11:30:28 +0200 Message-ID: <87ftsidcy3.fsf@linux.intel.com> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha256; protocol="application/pgp-signature" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-=-= Content-Type: text/plain Content-Transfer-Encoding: quoted-printable Nicolas Saenz Julienne writes: > Immediate data transfers (IDT) allow the HCD to copy small chunks of > data (up to 8bytes) directly into its output transfer TRBs. This avoids > the somewhat expensive DMA mappings that are performed by default on > most URBs submissions. > > In the case an URB was suitable for IDT. The data is directly copied > into the "Data Buffer Pointer" region of the TRB and the IDT flag is > set. Instead of triggering memory accesses the HC will use the data > directly. > > The implementation could cover all kind of output endpoints. Yet > Isochronous endpoints are bypassed as I was unable to find one that > matched IDT's constraints. As we try to bypass the default DMA mappings > on URB buffers we'd need to find a Isochronous device with an > urb->transfer_buffer_length <=3D 8 bytes. > > The implementation takes into account that the 8 byte buffers provided > by the URB will never cross a 64KB boundary. > > Signed-off-by: Nicolas Saenz Julienne This looks good to my eyes. Reviewed-by: Felipe Balbi =2D-=20 balbi --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEElLzh7wn96CXwjh2IzL64meEamQYFAlxtHjQACgkQzL64meEa mQZV1w/+IWvj6mmAZihLtdfVlQUdk0NlgtBLeQhRjQY/p8hjFVukOqwxfxbwDD2b 0Ft0HQFq8kZ3RY7Y4jjlcv6ubnU/XC7ctl89r7ovbqohcOpkbBhVzqMUEfW5tWhD +oNuaWjDUkxFo5fLB8HJo2d9wtrXRooXgdYBbYUiGXzkgt8Hjq7CJAIkqWgoKX0B NaQNIfbhvRjrtV7ASmOlSGG7nrbyARUwySzOC2rJeQ1iuwPONJTTcd87nUf+1om9 0/2BI9p3tBZsXbcqD6blZzOKXuC/vChx6Hn9PhCnkOS7VaqUr5ZSecqwS2NlHWx7 kjpebnSEMKslEsbZwhlV1NcyphU5+g3mbQC36HtGvZaqVyE06TBJH1CzzDU/ZgRi +OOfl9VRUI4aAhXQ5QgTV6N+qFLGK+v7XSYWcHZ0+ps8DMYTE4/Q5P8bYkodbt45 dz1VP1chJJGTCAKhxQfq+P1Pkr+5+pNdKaX+Y+FmZWm7CmVbndhh1VOO8uLBSn3G dystvflcoTg2ZpLAqXRgQFWqWUFArQsreDNJqKQjjTX/+valPl+Mo5wTutg0QQ3i fBRDa9fMqidDN2FDhWDBSyk8YEgQknykqiRBOWzLUKSoQduvOHqcX8TwQKMASaqk kPpjj8Vc4roluTLZwXf2A8IQX+0CabvAXOB0VyzCdS+fWLPVcb4= =Hceh -----END PGP SIGNATURE----- --=-=-=--