| Message ID | 20180711183239.21023-1-alexandre.belloni@bootlin.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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 <alexandre.belloni@bootlin.com> Why can't you have a real console driver that takes over at that point which respects whatever DT property you give it? The early_printk code is very raw and inefficient, and it shouldn't be used for anything but the debugging of early boot hangs. > --- > 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 > >
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 <alexandre.belloni@bootlin.com> > > 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 > > > > >
On Tue, 17 Jul 2018, Alexandre Belloni wrote: > 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 <alexandre.belloni@bootlin.com> > > > > 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 That is a good analysis, but not necessarily a good argument for this particular patch. > > 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. Yes, that certainly fits. This is not what your commit log message is saying though. > Also, atmel_serial doesn't yet have earlycon support. Fair enough, and probably something you should mention too. > > > --- > > > 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 >
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;
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 <alexandre.belloni@bootlin.com> --- arch/arm/kernel/early_printk.c | 3 +++ 1 file changed, 3 insertions(+)