From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934933AbcLNX7g (ORCPT ); Wed, 14 Dec 2016 18:59:36 -0500 Received: from pandora.armlinux.org.uk ([78.32.30.218]:60162 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934518AbcLNX7e (ORCPT ); Wed, 14 Dec 2016 18:59:34 -0500 Date: Wed, 14 Dec 2016 23:52:24 +0000 From: Russell King - ARM Linux To: Pali =?iso-8859-1?Q?Roh=E1r?= Cc: Arnd Bergmann , Robin Murphy , Linus Walleij , Ben Dooks , Tony Lindgren , Ivaylo Dimitrov , Sebastian Reichel , Aaro Koskinen , Pavel Machek , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] arm: dt: Initialize boot_command_line from CONFIG_CMDLINE in case DT does not provide /chosen/bootargs Message-ID: <20161214235224.GH14217@n2100.armlinux.org.uk> References: <1481749963-8664-1-git-send-email-pali.rohar@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1481749963-8664-1-git-send-email-pali.rohar@gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 14, 2016 at 10:12:43PM +0100, Pali Rohár wrote: > Commit 008a2ebcd677 ("ARM: dts: omap3: Remove skeleton.dtsi usage") broke > support for setting cmdline on Nokia N900 via CONFIG_CMDLINE. > > It is because arm code booted in DT mode parse cmdline only via function > early_init_dt_scan_chosen() and that function does not fill variable > boot_command_line when DTB does not contain /chosen entry. It is called > from function early_init_dt_scan_nodes() in setup_machine_fdt(). > > This patch fixes it by explicitly filling boot_command_line in function > setup_machine_fdt() after calling early_init_dt_scan_nodes() in case > boot_command_line still remains empty. This looks like a hack. First, the matter of the ATAGs compatibility. The decompressor relies on there being a pre-existing /chosen node to insert the command line and other parameters into. If we've dropped it (by dropping skeleton.dtsi) then we've just regressed more than just N900 - the decompressor won't be able to merge the ATAGs into the concatenated FDT. Second, CONFIG_CMDLINE has never been in place on DT systems - it's something atags_parse.c has been dealing with which isn't involved on DT. For DT, we expect the command line to be passed in. Now, given that, I find your commit message rather fishy. You seem to be claiming that CONFIG_CMDLINE used to work, but the fact is, we've never had it working on device tree systems. Instead, what I think was going on is that the bug you're seeing is that the removal of skeleton.dtsi results in the /chosen node being absent, which in turn prevents the decompressor picking the various parameters out of the ATAGs and dropping them into the DT blob. That, to me, sounds like a regression, and the fix is not to hack support for an unrelated feature, but to fix the original problem - and I think in this case, it's reasonable to ask for the offending commit to be reverted. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.