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 <[email protected]>
---
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 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 <[email protected]>
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 <[email protected]>
>
> 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
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 <[email protected]>
> >
> > 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
>