From patchwork Tue Nov 25 12:07:29 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ian Campbell X-Patchwork-Id: 5378071 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 2C1CAC11AC for ; Tue, 25 Nov 2014 12:10:18 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 01B4A20149 for ; Tue, 25 Nov 2014 12:10:17 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 05DF6200E1 for ; Tue, 25 Nov 2014 12:10:15 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1XtEuY-0000dw-C9; Tue, 25 Nov 2014 12:08:02 +0000 Received: from [2001:41c8:1:628a::89] (helo=benson.vm.bytemark.co.uk) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1XtEuT-0000a8-TD for linux-arm-kernel@lists.infradead.org; Tue, 25 Nov 2014 12:07:58 +0000 Received: from [185.25.64.249] (helo=kazak) by benson.vm.bytemark.co.uk with esmtpsa (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.72) (envelope-from ) id 1XtEu3-0003Zd-CG; Tue, 25 Nov 2014 12:07:31 +0000 Message-ID: <1416917249.32327.15.camel@debian.org> Subject: Re: [PATCH] of: support passing console options with stdout-path From: Ian Campbell To: Leif Lindholm Date: Tue, 25 Nov 2014 12:07:29 +0000 In-Reply-To: <20141125111724.GC2361@bivouac.eciton.net> References: <1416867838-18652-1-git-send-email-leif.lindholm@linaro.org> <20141125103504.GA21525@leverpostej> <20141125111724.GC2361@bivouac.eciton.net> X-Mailer: Evolution 3.12.7-1 Mime-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20141125_040758_283293_6B4AD75E X-CRM114-Status: GOOD ( 24.50 ) X-Spam-Score: 1.3 (+) Cc: Mark Rutland , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "robh+dt@kernel.org" , "grant.likely@linaro.org" , "plagnioj@jcrosoft.com" , "linux-arm-kernel@lists.infradead.org" X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_LOW, T_RP_MATCHES_RCVD,UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Tue, 2014-11-25 at 11:17 +0000, Leif Lindholm wrote: > On Tue, Nov 25, 2014 at 10:35:04AM +0000, Mark Rutland wrote: > > On Mon, Nov 24, 2014 at 10:23:58PM +0000, Leif Lindholm wrote: > > > Support specifying console options (like with console=ttyXN,) > > > by appending them to the stdout-path property after a separating ':'. > > > > > > Example: > > > stdout-path = "uart0:115200"; > > > > I would very much like to be able to use this -- it will allow > > distributions to boot on a board without having to know _anything_ about > > the console UART until userspace is up, which would make it possible to > > have a completely generic installer image, without requiring the > > platform to provide bootargs. > > > > My only concern is that this conflates the set of kernel command line > > options for the UART wit the DT binding for it. I don't know how good > > people are at keeping those options stable, and I know they are > > currently not documented -- we would need to add a stdout-path options > > section to relevant UART bindings. > > I don't disagree. > > Current options are fairly well defined and stable, at least for any > driver that uses uart_parse_options() (documented in > Documentation/serial/driver). My concern is that this is Linux specific, other OSes may have different ideas about how stdout options should be formatted within this property. (At least I don't know of any standardisation of the 115200n8 thing -- I'd love to be corrected!) If I were a firmware author I'd be wary of specifying a stdout-path with a Linux specific suffix. Search ePAPR for baud it seems that the generic serial binding includes a current-speed property in 6.2.1.2. It then goes on a bit ambiguously to talk about the NS16550 in 6.2.2 but I think 6.2.1.2 was intended to be generic. No mention of stop-bits/parity etc though, they are assumed to be set already I think One thought I had was to define a dt-stdout "pseudo-console" so that console=dt-stdout,115200n8 or something could be used. Anyway I applied your patch to v3.18-rc5 and ran it on a Mustang and it didn't work for some reason. I'm using: fdt set /chosen stdout-path "/soc/serial@1c020000:115200" setenv bootargs "earlycon=uart8250,mmio32,0x1c020000 root=/dev/sda3 rw debug" So I get earlycon but then no proper console. Removing earlycon just makes that stop working. With: I can see in dmesg: [ 0.000000] of_alias_scan: name=/soc/serial@1c020000:115200 of_stdout= (null) options=115200 So it seems like of_find_node_by_path() is confused by the ":". I've not tried it but I'd have expected something more like: if (name) { of_stdout_options = strchr(name, ':'); if (of_stdout_options != NULL) { *of_stdout_options = '0'; of_stdout_options++; } of_stdout = of_find_node_by_path(name); } i.e. strip the options then do the patch lookup. name is const so this won't actually work, but something like it... Ian. diff --git a/drivers/of/base.c b/drivers/of/base.c index 89c6b33..5dc1718 100644 --- a/drivers/of/base.c +++ b/drivers/of/base.c @@ -1840,6 +1840,8 @@ void of_alias_scan(void * (*dt_alloc)(u64 size, u64 align)) of_stdout_options = strchr(name, ':'); if (of_stdout_options != NULL) of_stdout_options++; + printk(KERN_CRIT "%s: name=%s of_stdout=%p options=%s\n", + __func__, name, of_stdout, of_stdout_options); } }