From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752295AbaIAC31 (ORCPT ); Sun, 31 Aug 2014 22:29:27 -0400 Received: from mail-pa0-f42.google.com ([209.85.220.42]:65101 "EHLO mail-pa0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752056AbaIAC3Z (ORCPT ); Sun, 31 Aug 2014 22:29:25 -0400 From: Sahara X-Google-Original-From: Sahara Date: Mon, 1 Sep 2014 11:28:47 +0900 (KST) To: Stephen Warren cc: Sahara , Thierry Reding , akpm@linux-foundation.org, keun-o.park@windriver.com, hpa@zytor.com, rafael.j.wysocki@intel.com, peterz@infradead.org, rusty@rustcorp.com.au, kirill.shutemov@linux.intel.com, oleg@redhat.com, prarit@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] earlyprintk: re-enable earlyprintk calling early_param In-Reply-To: <5400A2BD.8080508@wwwdotorg.org> Message-ID: References: <1408011216-8621-1-git-send-email-kpark3469@gmail.com> <20140827151504.GA22824@ulmo> <5400A2BD.8080508@wwwdotorg.org> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 29 Aug 2014, Stephen Warren wrote: > On 08/28/2014 11:28 PM, Sahara wrote: >> >> >> On Wed, 27 Aug 2014, Thierry Reding wrote: >> >>> On Thu, Aug 14, 2014 at 07:13:36PM +0900, kpark3469@gmail.com wrote: >>>> From: Sahara >>>> >>>> Although there are many obs_kernel_param and its names are >>>> earlyprintk and also EARLY_PRINTK is also enabled, we could not >>>> see the early_printk output properly until now. This patch >>>> considers earlycon as well as earlyprintk. >>>> >>>> Signed-off-by: Sahara >>>> --- >>>> init/main.c | 3 ++- >>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/init/main.c b/init/main.c >>>> index bb1aed9..235d248 100644 >>>> --- a/init/main.c >>>> +++ b/init/main.c >>>> @@ -426,7 +426,8 @@ static int __init do_early_param(char *param, char >> *val, const char *unused) >>>> for (p = __setup_start; p < __setup_end; p++) { >>>> if ((p->early && parameq(param, p->str)) || >>>> (strcmp(param, "console") == 0 && >>>> - strcmp(p->str, "earlycon") == 0) >>>> + ((strcmp(p->str, "earlycon") == 0) || >>>> + (strcmp(p->str, "earlyprintk") == 0))) >>>> ) { >>>> if (p->setup_func(val) != 0) >>>> pr_warn("Malformed early option '%s'\n", >> param); >>> >>> It seems like this patch causes the following warning for me during >>> boot: >>> >>> [ 0.000000] Booting Linux on physical CPU 0x0 >>> [ 0.000000] Initializing cgroup subsys cpu >>> [ 0.000000] Initializing cgroup subsys cpuacct >>> [ 0.000000] Linux version 3.17.0-rc2-next-20140827 >> (thierry.reding@ulmo) (gcc version 4.9.0 (GCC) ) #18 SMP PREEMPT Wed Aug >> 27 17:08:12 CEST 2014 >>> [ 0.000000] CPU: ARMv7 Processor [413fc0f3] revision 3 (ARMv7), >> cr=10c5387d >>> [ 0.000000] CPU: PIPT / VIPT nonaliasing data cache, PIPT instruction >> cache >>> [ 0.000000] Machine model: NVIDIA Tegra124 Jetson TK1 >>> [ 0.000000] bootconsole [earlycon0] enabled >>> [ 0.000000] debug: ignoring loglevel setting. >>> [ 0.000000] ------------[ cut here ]------------ >>> [ 0.000000] WARNING: CPU: 0 PID: 0 at >> /home/thierry.reding/src/kernel/linux-work.git/kernel/printk/printk.c:2402 >> register_console+0x60/0x37c() >>> [ 0.000000] console 'earlycon0' already registered >>> [ 0.000000] Modules linked in: >>> [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted >> 3.17.0-rc2-next-20140827 #18 >>> [ 0.000000] [] (unwind_backtrace) from [] >> (show_stack+0x10/0x14) >>> [ 0.000000] [] (show_stack) from [] >> (dump_stack+0x98/0xd8) >>> [ 0.000000] [] (dump_stack) from [] >> (warn_slowpath_common+0x70/0x8c) >>> [ 0.000000] [] (warn_slowpath_common) from [] >> (warn_slowpath_fmt+0x30/0x40) >>> [ 0.000000] [] (warn_slowpath_fmt) from [] >> (register_console+0x60/0x37c) >>> [ 0.000000] [] (register_console) from [] >> (setup_early_printk+0x20/0x28) >>> [ 0.000000] [] (setup_early_printk) from [] >> (do_early_param+0x6c/0xd0) >>> [ 0.000000] [] (do_early_param) from [] >> (parse_args+0x238/0x3d0) >>> [ 0.000000] [] (parse_args) from [] >> (parse_early_options+0x38/0x40) >>> [ 0.000000] [] (parse_early_options) from [] >> (parse_early_param+0x30/0x40) >>> [ 0.000000] [] (parse_early_param) from [] >> (setup_arch+0x4b4/0x974) >>> [ 0.000000] [] (setup_arch) from [] >> (start_kernel+0x98/0x3a8) >>> [ 0.000000] [] (start_kernel) from [<80008074>] >> (0x80008074) >>> [ 0.000000] ---[ end trace cb88537fdc8fa200 ]--- >>> [ 0.000000] cma: Reserved 128 MiB at a7800000 >>> [ 0.000000] Memory policy: Data cache writealloc >>> [ 0.000000] On node 0 totalpages: 524032 >>> [ 0.000000] free_area_init_node: node 0, pgdat c091cc00, node_mem_map >> e67b7000 >>> [ 0.000000] Normal zone: 1520 pages used for memmap >>> [ 0.000000] Normal zone: 0 pages reserved >>> [ 0.000000] Normal zone: 194560 pages, LIFO batch:31 >>> [ 0.000000] HighMem zone: 2574 pages used for memmap >>> [ 0.000000] HighMem zone: 329472 pages, LIFO batch:31 >>> [ 0.000000] PERCPU: Embedded 8 pages/cpu @e6767000 s8832 r8192 d15744 >> u32768 >>> [ 0.000000] pcpu-alloc: s8832 r8192 d15744 u32768 alloc=8*4096 >>> [ 0.000000] pcpu-alloc: [0] 0 [0] 1 [0] 2 [0] 3 >>> [ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. >> Total pages: 522512 >>> [ 0.000000] Kernel command line: console=ttyS0,115200n8 >> ignore_loglevel rootwait ro earlyprintk ip=:::::eth0:dhcp root=/dev/nfs >> nfsroot=192.168.69.100:/srv/nfs/tegra124 drm.debug=0xf cma=128M >>> >>> Reverting the patch eliminates the warning. earlyprintk does work fine >>> for me without this patch. >>> >>> Thierry >> >> >> This warning message is caused by specifying 'earlyprintk' in >> your command line args. Same problem may happen if you specify 'earlycon' >> in your command line args and enable CONFIG_SERIAL_EARLYCON with >> the current code without this patch. I think it's appropriate result >> letting a developer know that both ways of using earlyprintk are enabled. >> With current code, although a developer enables CONFIG_EARLY_PRINTK and >> has "console=" arg in command line args, he/she should specify the >> 'earlyprintk' in command line args also to see early_printk() outputs. >> With this patch, simply enabling CONFIG_EARLY_PRINTK and having 'console=' >> line make you be able to the early_printk(). >> >> Nonetheless I want to retract this patch. It's good for ARM, but not good >> for other architectures such as x86. And, because CONFIG_EARLY_PRINTK is >> depending on DEBUG_LL in ARM, making a relation with "console=" is absurd. >> (see strcmp(param, "console") == 0 && strcmp(p->str, "earlyprintk") == 0) > > Even on ARM, this patch feels like the wrong thing. After all, I can build a > DEBUG_LL enabled multi-platform kernel, and boot it on a bunch of different > SoCs. However, earlyprintk will only work on one (or zero) of those SoCs, and > hence shouldn't automatically enable itself; specifically requesting > activation using the earlyprintk kernel command-line parameter is the correct > approach. > So you are saying, because DEBUG_LL didn't work on several SoCs, using the earlyprintk in command line args is the correct approach? You are misunderstanding how it works. On ARM with enabling multi-platform kernel, you should choose a specific low-level debug port for DEBUG_LL. For example, if you have OMAP ZOOM3, you should select CONFIG_DEBUG_ZOOM_UART from menu. If you chose a right port for your SoCs and if it didn't work properly, that means its port code should be fixed. (Please report it.) All the code for low-level debugging is located at arch/arm/include/debug. - Sahara