From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 79655B7B68 for ; Thu, 17 Sep 2009 07:31:35 +1000 (EST) Subject: Re: RFC: delete UART current-speed from 4xx DTS? From: Benjamin Herrenschmidt To: Josh Boyer In-Reply-To: <20090916131943.GA14261@zod.rchland.ibm.com> References: <20090915143135.GA7015@windriver.com> <20090915153220.GG12372@zod.rchland.ibm.com> <1253051047.8375.232.camel@pasglop> <20090916131943.GA14261@zod.rchland.ibm.com> Content-Type: text/plain Date: Thu, 17 Sep 2009 07:31:06 +1000 Message-Id: <1253136666.8375.288.camel@pasglop> Mime-Version: 1.0 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: , > 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. Well, I've always wondered why we just don't put the probe in the 8250 driver... I proposed it on the list a while back and there was no serious objection, but then forgot about it :-) We should do it, and check if the result is sane (looks like a standard speed). If it is, we should then just used it. Ben.