From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752384AbcGSF0Y (ORCPT ); Tue, 19 Jul 2016 01:26:24 -0400 Received: from mga02.intel.com ([134.134.136.20]:49950 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752004AbcGSF0V (ORCPT ); Tue, 19 Jul 2016 01:26:21 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.28,388,1464678000"; d="scan'208";a="736447050" Date: Mon, 18 Jul 2016 22:30:38 -0700 From: Bin Gao To: Greg Kroah-Hartman Cc: Felipe Balbi , Heikki Krogerus , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Bin Gao , Chandra Sekhar Anagani Subject: Re: [PATCH 1/2] usb: typec: Add USB Power Delivery sink port support Message-ID: <20160719053038.GA90550@worksta> References: <20160715021405.GB128987@worksta> <87mvljgp9n.fsf@linux.intel.com> <20160715111141.GB23645@kroah.com> <87k2gngn8z.fsf@linux.intel.com> <20160715224110.GB159605@worksta> <20160715234953.GB30372@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160715234953.GB30372@kroah.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jul 16, 2016 at 08:49:53AM +0900, Greg Kroah-Hartman wrote: > On Fri, Jul 15, 2016 at 03:41:10PM -0700, Bin Gao wrote: > > On Fri, Jul 15, 2016 at 02:21:48PM +0300, Felipe Balbi wrote: > > > Greg Kroah-Hartman writes: > > > > On Fri, Jul 15, 2016 at 01:38:12PM +0300, Felipe Balbi wrote: > > > >> > > > >> Hi, > > > >> > > > >> Bin Gao writes: > > > >> > +static void print_message(int port, bool is_cmsg, u8 msg, bool recv) > > > >> > +{ > > > >> > + pr_info("sink port %d: %s message %s %s\n", port, > > > >> > + is_cmsg ? "Control" : "Data", > > > >> > + msg_to_string(is_cmsg, msg), > > > >> > + recv ? "received" : "sent(wait GOODCRC)"); > > > >> > +} > > > >> > > > >> this is problematic. By default, we're all using 115200 8N1 baud > > > >> rate. This message alone prints anywhere from 50 to 100 characters (I > > > >> didn't really count properly, these are rough numbers), and that takes: > > > >> > > > >> n50chars_time = 50 / (115200 / 10) = 4.3ms > > > >> n100chars_time = 100 / (115200 / 10) = 8.6ms > > > >> > > > >> Considering you have 30ms to reply with Power Request after GoodCRC, and > > > >> considering you're printing several of these messages, they become > > > >> really expensive and eat up valuable time from tSenderReply. > > > > > > > > printk() should be async, so it shouldn't be that big of a deal. > > > > > > I can actually see this causing problems ;-) With this pr_info(), > > > sometimes tSenderReply times out and Source gives a HardReset. Without > > > pr_info(), type-c analyzer tells me we reply in less than 1ms. > > > > > > > What is wrong is that this isn't using dev_info(). > > > > > > right, that too. > > > > > > -- > > > balbi > > > > When we don't have a struct device pointer for this driver, > > Then you should fix that, as this is a driver for hardware :) This is actualy a software stack to implement the USB PD spec. Only the USB Type-C phy driver has a device pointer. The PD stack vs. USB Type-C phy driver is similar to TCP/IP stack vs. ethernet driver in the kernel. We don't have a device pointer for TCP/IP stack code either. Thanks, Bin > > thanks, > > greg k-h