From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752786AbcHIMun (ORCPT ); Tue, 9 Aug 2016 08:50:43 -0400 Received: from mailapp01.imgtec.com ([195.59.15.196]:52474 "EHLO mailapp01.imgtec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752345AbcHIMui (ORCPT ); Tue, 9 Aug 2016 08:50:38 -0400 From: Paul Burton To: CC: Ralf Baechle , Paul Burton , Tejun Heo , Sergey Senozhatsky , Tony Luck , Jiri Slaby , Daniel Vetter , Russell King , Emil Velikov , Ivan Delalande , Thierry Reding , Petr Mladek , , Geliang Tang , Dave Young , Greg Kroah-Hartman , , Rob Herring , Frank Rowand , Mathias Krause , Andrew Morton Subject: [PATCH] console: Don't prefer first registered if DT specifies stdout-path Date: Tue, 9 Aug 2016 13:50:10 +0100 Message-ID: <20160809125010.14150-1-paul.burton@imgtec.com> X-Mailer: git-send-email 2.9.2 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.100.200.230] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If a device tree specifies a preferred device for kernel console output via the stdout-path or linux,stdout-path chosen node properties or the stdout alias then the kernel ought to honor it & output the kernel console to that device. As it stands, this isn't the case. Whilst we parse the stdout-path properties & set an of_stdout variable from of_alias_scan(), and use that from of_console_check() to determine whether to add a console device as a preferred console whilst registering it, we also prefer the first registered console if no other has been selected at the time of its registration. This means that if a console other than the one the device tree selects via stdout-path is registered first, we will switch to using it & when the stdout-path console is later registered the call to add_preferred_console() via of_console_check() is too late to do anything useful. In practice this seems to mean that we switch to the dummy console device fairly early & see no further console output: Console: colour dummy device 80x25 console [tty0] enabled bootconsole [ns16550a0] disabled Fix this by not automatically preferring the first registered console if one is specified by the device tree. This allows consoles to be registered but not enabled, and once the driver for the console selected by stdout-path calls of_console_check() the driver will be added to the list of preferred consoles before any other console has been enabled. When that console is then registered via register_console() it will be enabled as expected. Signed-off-by: Paul Burton --- drivers/of/base.c | 2 ++ include/linux/console.h | 6 ++++++ kernel/printk/printk.c | 13 ++++++++++++- 3 files changed, 20 insertions(+), 1 deletion(-) diff --git a/drivers/of/base.c b/drivers/of/base.c index ebf84e3..2ea6877 100644 --- a/drivers/of/base.c +++ b/drivers/of/base.c @@ -1974,6 +1974,8 @@ void of_alias_scan(void * (*dt_alloc)(u64 size, u64 align)) name = of_get_property(of_aliases, "stdout", NULL); if (name) of_stdout = of_find_node_opts_by_path(name, &of_stdout_options); + if (of_stdout) + console_set_by_of(); } if (!of_aliases) diff --git a/include/linux/console.h b/include/linux/console.h index 98c8615..71cc04f 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -166,6 +166,12 @@ static inline void console_sysfs_notify(void) #endif extern bool console_suspend_enabled; +#ifdef CONFIG_OF +extern void console_set_by_of(void); +#else +static inline void console_set_by_of(void); +#endif + /* Suspend and resume console messages over PM events */ extern void suspend_console(void); extern void resume_console(void); diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 60cdf63..f1f03ca 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -149,6 +149,17 @@ static int preferred_console = -1; int console_set_on_cmdline; EXPORT_SYMBOL(console_set_on_cmdline); +#ifdef CONFIG_OF +static bool of_specified_console; + +void console_set_by_of(void) +{ + of_specified_console = true; +} +#else +# define of_specified_console false +#endif + /* Flag: console code may call schedule() */ static int console_may_schedule; @@ -2509,7 +2520,7 @@ void register_console(struct console *newcon) * didn't select a console we take the first one * that registers here. */ - if (preferred_console < 0) { + if (preferred_console < 0 && !of_specified_console) { if (newcon->index < 0) newcon->index = 0; if (newcon->setup == NULL || -- 2.9.2