From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e5.ny.us.ibm.com (e5.ny.us.ibm.com [32.97.182.145]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e5.ny.us.ibm.com", Issuer "Equifax" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id 11E5CB7B7D for ; Wed, 16 Sep 2009 23:19:49 +1000 (EST) Received: from d01relay04.pok.ibm.com (d01relay04.pok.ibm.com [9.56.227.236]) by e5.ny.us.ibm.com (8.14.3/8.13.1) with ESMTP id n8GDAuGQ004155 for ; Wed, 16 Sep 2009 09:10:56 -0400 Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id n8GDJkR5224964 for ; Wed, 16 Sep 2009 09:19:46 -0400 Received: from d01av04.pok.ibm.com (loopback [127.0.0.1]) by d01av04.pok.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id n8GDJjOw005979 for ; Wed, 16 Sep 2009 09:19:45 -0400 Date: Wed, 16 Sep 2009 09:19:43 -0400 From: Josh Boyer To: Benjamin Herrenschmidt Subject: Re: RFC: delete UART current-speed from 4xx DTS? Message-ID: <20090916131943.GA14261@zod.rchland.ibm.com> References: <20090915143135.GA7015@windriver.com> <20090915153220.GG12372@zod.rchland.ibm.com> <1253051047.8375.232.camel@pasglop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1253051047.8375.232.camel@pasglop> Cc: Paul Gortmaker , linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, Sep 16, 2009 at 07:44:07AM +1000, Benjamin Herrenschmidt wrote: >On Tue, 2009-09-15 at 11:32 -0400, Josh Boyer wrote: >> On Tue, Sep 15, 2009 at 10:31:36AM -0400, Paul Gortmaker wrote: >> >One of the guys here was getting a messed up console on a bamboo board >> >(on linux boot), which he traced to the fact that the default dts has a >> >9600 baudrate coded into it (board was running 115k2, not 9600). Either >> >deleting the line, or replacing the 9600 with zero fixed the problem. >> >> Once booted, was there a valid current-speed property in /proc/device-tree >> for the serial node? I'm curious if U-Boot created it, or if the kernel >> just used whatever baud was present already. >> >> When I did the bamboo port a while ago, I recall having issues with either >> a missing clock-frequency or current-speed (or both perhaps) and the bootloader >> on the board was the original PIBS. It might have been an issue with PIBS >> but I'm guessing the rest of the 4xx boards copied from either Ebony or >> Bamboo in their ports and hence contain that property. > >I think I recently added code to legacy_serial probe the speed from the >HW if the property is absent, which should help. Ok, so I think that is related to what I originally hit. I played around with removing the current-speed property on canyonlands today, and noticed that I would get no console output at all unless I specified a baudrate with console=ttyS0,115200. That was sort of contrary to what I found with bamboo, so I diffed the configs to see why. Bamboo has udbg enabled and hence has legacy_serial builtin, whereas canyonlands just has of_serial. So on boards where of_serial is the only serial driver, we need either an accurate current-speed property, or a specific baudrate on the command line. That makes a bit more tenuous to remove the properties entirely, because if people disable udbg and are relying on that behavior they get no more console output. Need to think on that a bit I guess. Alternatively, we could try patching of_serial.c to do the baudrate probe as well. josh