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 52F48C43381 for ; Tue, 19 Mar 2019 08:13:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2D58A20850 for ; Tue, 19 Mar 2019 08:13:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727720AbfCSINI (ORCPT ); Tue, 19 Mar 2019 04:13:08 -0400 Received: from mga06.intel.com ([134.134.136.31]:17178 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727395AbfCSINI (ORCPT ); Tue, 19 Mar 2019 04:13:08 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 19 Mar 2019 01:13:07 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,497,1544515200"; d="scan'208";a="123866441" Received: from mattu-haswell.fi.intel.com (HELO [10.237.72.164]) ([10.237.72.164]) by orsmga007.jf.intel.com with ESMTP; 19 Mar 2019 01:13:05 -0700 Subject: Re: [PATCH] usb: xhci: add Immediate Data Transfer support To: Nicolas Saenz Julienne , Mathias Nyman Cc: felipe.balbi@linux.intel.com, oneukum@suse.com, Greg Kroah-Hartman , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org References: <20190219162945.22889-1-nsaenzjulienne@suse.de> <31a3530dbd75771c82bfb41a357370b90d7981d2.camel@suse.de> From: Mathias Nyman Message-ID: <1fe79a10-16d4-8d06-4c9b-7e5a3d3807cf@linux.intel.com> Date: Tue, 19 Mar 2019 10:15:18 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <31a3530dbd75771c82bfb41a357370b90d7981d2.camel@suse.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15.3.2019 14.51, Nicolas Saenz Julienne wrote: > On Tue, 2019-02-19 at 17:29 +0100, Nicolas Saenz Julienne wrote: >> 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 <= 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 > > > Friendly ping, any more comments on this? :) > Looks good, adding to queue, thanks -Mathias