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 8E4BCC43441 for ; Fri, 16 Nov 2018 12:54:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5858D2087A for ; Fri, 16 Nov 2018 12:54:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5858D2087A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=codethink.co.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389749AbeKPXGS (ORCPT ); Fri, 16 Nov 2018 18:06:18 -0500 Received: from imap1.codethink.co.uk ([176.9.8.82]:50426 "EHLO imap1.codethink.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389692AbeKPXGR (ORCPT ); Fri, 16 Nov 2018 18:06:17 -0500 Received: from [78.40.148.180] (helo=[0.0.0.0]) by imap1.codethink.co.uk with esmtpsa (Exim 4.84_2 #1 (Debian)) id 1gNddG-0006uA-G4; Fri, 16 Nov 2018 12:53:58 +0000 Subject: Re: [PATCH] USB: host: ehci: allow tine of highspeed nak-count To: Alan Stern , Ben Dooks Cc: gregkh@linuxfoundation.org, linux-usb@vger.kernel.org, linux-kernel@lists.codethink.co.uk, linux-kernel@vger.kernel.org References: From: Ben Dooks Organization: Codethink Limited. Message-ID: <39eb9e8b-2b5d-ea75-3232-be77c3743dbc@codethink.co.uk> Date: Fri, 16 Nov 2018 12:53:57 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14/11/18 18:47, Alan Stern wrote: > On Wed, 14 Nov 2018, Ben Dooks wrote: > >> From: Ben Dooks >> >> At least some systems benefit with less scheduling if the NAK count >> value is set higher than the default 4. For instance a Tegra3 with >> an SMSC9512 showed less interrupt load when this was changed to 14. > > Interesting. Why do you think this is? In theory, increasing the NAK > count RL value should cause a higher memory bus load and perhaps a > slight rise in the interrupt load (transfers will complete a little > more quickly because the controller tries harder to poll the endpoints > and see if they are ready). I thought the NAK counter was decremented until the transfer is given up on. I'm going to have to go back and get some actual figures from a running system as this was originally done over a year ago with the SMSC9512 (IIRC) network driver. >> To allow the changing of this value, add a sysfs node to each of >> the controllers to allow run-time changing. >> >> Signed-off-by: Ben Dooks > > The patch looks okay to me. I'll look at getting some tracing from the SMSC driver to see what is going on. -- Ben Dooks http://www.codethink.co.uk/ Senior Engineer Codethink - Providing Genius https://www.codethink.co.uk/privacy.html