From mboxrd@z Thu Jan 1 00:00:00 1970 From: alexandre.belloni@bootlin.com (Alexandre Belloni) Date: Tue, 17 Jul 2018 22:31:53 +0200 Subject: [PATCH] ARM: early_printk: respect keep parameter In-Reply-To: References: <20180711183239.21023-1-alexandre.belloni@bootlin.com> Message-ID: <20180717203153.GC3211@piout.net> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 17/07/2018 16:16:44-0400, Nicolas Pitre wrote: > On Wed, 11 Jul 2018, Alexandre Belloni wrote: > > > Parse and use the keep parameter of earlyprintk to avoid having the kernel > > output stop with: > > > > Console: colour dummy device 80x30 > > console [tty0] enabled > > bootconsole [earlycon0] disabled > > > > This happens because once tty0, the virtual terminal console is registered, > > it is selected as the default console, disregarding an existing stdout-path > > DT property and the early console is shutdown before the console driver is > > probed. > > > > Signed-off-by: Alexandre Belloni > > Why can't you have a real console driver that takes over at that point > which respects whatever DT property you give it? > See Russell's analysis here: https://www.spinics.net/lists/linux-serial/msg25363.html > The early_printk code is very raw and inefficient, and it shouldn't be > used for anything but the debugging of early boot hangs. > The issue I had is that he pinctrl driver wasn't probing so the real console driver could never probe. I think this fits the use case. Also, atmel_serial doesn't yet have earlycon support. > > --- > > arch/arm/kernel/early_printk.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/arch/arm/kernel/early_printk.c b/arch/arm/kernel/early_printk.c > > index 9257736ec9fa..bbb10150b11a 100644 > > --- a/arch/arm/kernel/early_printk.c > > +++ b/arch/arm/kernel/early_printk.c > > @@ -42,6 +42,9 @@ static struct console early_console_dev = { > > > > static int __init setup_early_printk(char *buf) > > { > > + if (buf && strstr(buf, "keep")) > > + early_console_dev.flags &= ~CON_BOOT; > > + > > early_console = &early_console_dev; > > register_console(&early_console_dev); > > return 0; > > -- > > 2.18.0 > > > > > -- Alexandre Belloni, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com