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=-2.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,USER_AGENT_MUTT 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 B678AC65BAF for ; Wed, 12 Dec 2018 15:53:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 757382084E for ; Wed, 12 Dec 2018 15:53:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ti.com header.i=@ti.com header.b="GYOAd30v" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 757382084E Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=ti.com 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 S1727847AbeLLPxg (ORCPT ); Wed, 12 Dec 2018 10:53:36 -0500 Received: from lelv0143.ext.ti.com ([198.47.23.248]:40758 "EHLO lelv0143.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726358AbeLLPxg (ORCPT ); Wed, 12 Dec 2018 10:53:36 -0500 Received: from lelv0265.itg.ti.com ([10.180.67.224]) by lelv0143.ext.ti.com (8.15.2/8.15.2) with ESMTP id wBCFrEvd128567; Wed, 12 Dec 2018 09:53:14 -0600 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1544629994; bh=IRkFaSyvsOf5vf2b5eQr89QFmegthVjV9uUCXEA+Xjg=; h=Date:From:To:CC:Subject:References:In-Reply-To; b=GYOAd30vU8iOqki+2sgJMJ09Hg+Mu1ffTPETbehi14Xy75dzJB1WGqfYE3vMc67e+ oxfxSVw0zFvTOkQ9JC3/R5FyY+g6Xpl5WEfQALr36dmYPMig3tUrIwaV81MwdsdpWA BpGActErhYKyOFsR+se4YPbndS3bIE2j/+E1jbjg= Received: from DLEE101.ent.ti.com (dlee101.ent.ti.com [157.170.170.31]) by lelv0265.itg.ti.com (8.15.2/8.15.2) with ESMTPS id wBCFrDkP051833 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Wed, 12 Dec 2018 09:53:13 -0600 Received: from DLEE107.ent.ti.com (157.170.170.37) by DLEE101.ent.ti.com (157.170.170.31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1591.10; Wed, 12 Dec 2018 09:53:13 -0600 Received: from dflp32.itg.ti.com (10.64.6.15) by DLEE107.ent.ti.com (157.170.170.37) with Microsoft SMTP Server (version=TLS1_0, cipher=TLS_RSA_WITH_AES_256_CBC_SHA) id 15.1.1591.10 via Frontend Transport; Wed, 12 Dec 2018 09:53:13 -0600 Received: from localhost (ileax41-snat.itg.ti.com [10.172.224.153]) by dflp32.itg.ti.com (8.14.3/8.13.8) with ESMTP id wBCFrDBg032099; Wed, 12 Dec 2018 09:53:13 -0600 Date: Wed, 12 Dec 2018 09:53:13 -0600 From: Bin Liu To: Peter Chen CC: , , , Greg Kroah-Hartman , , , lkml , , , , , , , , Subject: Re: [PATCH v1 2/2] usb:cdns3 Add Cadence USB3 DRD Driver Message-ID: <20181212155313.GA6502@uda0271908> Mail-Followup-To: Bin Liu , Peter Chen , pawell@cadence.com, balbi@kernel.org, devicetree@vger.kernel.org, Greg Kroah-Hartman , linux-usb@vger.kernel.org, rogerq@ti.com, lkml , adouglas@cadence.com, jbergsagel@ti.com, nsekhar@ti.com, nm@ti.com, sureshp@cadence.com, peter.chen@nxp.com, pjez@cadence.com, kurahul@cadence.com References: <1544445555-17325-1-git-send-email-pawell@cadence.com> <1544445555-17325-3-git-send-email-pawell@cadence.com> <87h8fkmfar.fsf@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter, On Wed, Dec 12, 2018 at 10:04:25AM +0800, Peter Chen wrote: [snip] > > >I strongly advise against using dev_dbg() for debugging. Even more so > > >inside your IRQ handler. > > Felipe, I use Dynamic Debug for debugging, and show debug messages with > "dmesg" after testing/debugging. I see dwc3 using trace, any benefits > for switching > to trace? The benefits I see are - *by default*, the debug log doesn't have to go through uart console, which is slow. I typically 'cat trace_pipe' from a telnet which is much faster then uart. But Dynamic Debug log by default got printed on uart, I have to set printk level to not print them, which is an extra step. - tracepoint uses one place to decode the message vs DD has to repeat the similar print statement in the code; and tracepoint decodes it offline which reduce the kernel runtime overhead too. - with tracepoint, it is easier to turn on debug for a specific group of messages. - you can adjust the ftrace buffer size at runtime. can we do that for printk? I don't remember. Regards, -Bin.