Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752252AbaL2TKD (ORCPT ); Mon, 29 Dec 2014 14:10:03 -0500 Received: from mout.kundenserver.de ([212.227.17.13]:58678 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751061AbaL2TKA (ORCPT ); Mon, 29 Dec 2014 14:10:00 -0500 From: Arnd Bergmann To: Eddie Huang Cc: Rob Herring , Mark Rutland , Greg Kroah-Hartman , Matthias Brugger , srv_heupstream@mediatek.com, Rob Herring , Pawel Moll , Ian Campbell , Kumar Gala , Catalin Marinas , Will Deacon , Jiri Slaby , Alan Cox , "devicetree@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-serial@vger.kernel.org" , Sascha Hauer , yingjoe.chen@mediatek.com, yh.chen@mediatek.com Subject: Re: [PATCH 1/2] tty: serial: 8250_mtk: Add earlycon Date: Mon, 29 Dec 2014 20:08:59 +0100 Message-ID: <16342339.NQnBcp9YuE@wuerfel> User-Agent: KMail/4.11.5 (Linux/3.16.0-10-generic; KDE/4.11.5; x86_64; ; ) In-Reply-To: <1419827096.6184.128.camel@mtksdaap41> References: <1418891601-53769-1-git-send-email-eddie.huang@mediatek.com> <1419827096.6184.128.camel@mtksdaap41> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V03:K0:SucAS9NHwG6g20ibYlhYkgo45o4oHBhypLs6z0u4GehEFiAtLJP XbXi4ZDq2bHA2j5C/G7pszX5slV5feFRH3RG1d/BzBC7qllPlYR4xeUHa2WtoymiJb1DLym FIhwOCDNY3KQP9gjKsiIYhsStwonv5JeAsJI320EYX8NDHI0srGHmEcAH4fAgY9zwLpBrBQ HpDjQO+BgaJxL+fHi/Ckw== X-UI-Out-Filterresults: notjunk:1; Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday 29 December 2014 12:24:56 Eddie Huang wrote: > Hi Rob, > > On Fri, 2014-12-26 at 15:24 -0600, Rob Herring wrote: > > On Thu, Dec 18, 2014 at 2:33 AM, Eddie Huang wrote: > > > Mediatek UART has highspeed register, but 8250_early.c doesn't > > > support this, so add earlycon in 8250_mtk.c > > > > I don't see any highspeed register setup here. More generically, > > aren't you just skipping any UART setup? That may be useful on other > > platforms with 8250s, too. With the kernel command line version, you > > could perhaps add a "noinit" flag. The DT case is harder, and I'm not > > sure how we should handle that. We could perhaps add a > > "stdout-path-initialized" flag to chosen. > > > > Yes, I skipped UART setup same as msm_serial.c and amba-pl011.c > (although they are standalone serial driver). Just like earlyprintk, I > think earlycon should reuse UART setting in loader. Since some other > platforms with 8250 already depend on this, it's ok to add flags to > distinguish whether 8250 earlycon driver should init hw or not. As you > said, add "noinit" flag is simple, but "stdout-path-initialized" need > more discussion. It would definitely be nice to have consistent behavior, and I also think it would be good to default to noinit for the console, because that is the more likely case. Basically anything that can do debug_ll on ARM already depends on this behavior because the debug_ll infrastructure does not initialize the console before using it. I believe the same is true for powerpc udbg. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/