[RESEND PATCH] arm64: dts: specify console via command line

[RESEND PATCH] arm64: dts: specify console via command line

[Chunyan Zhang]

From: Chunyan Zhang <chunyan.zhang@unisoc.com>

The SPRD serial driver need to know which serial port would be used as
console in an early period during initialization, otherwise console
init would fail since we added this feature[1].

So this patch add console to command line via devicetree.

[1] https://lore.kernel.org/lkml/20190826072929.7696-4-zhang.lyra@gmail.com/

Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
---
I guess no comments on this, so resending this and add soc@kernel.org,
hope Arnd or Olof can help to merge into arch_arm tree.

Thanks,
Chunyan
---
 arch/arm64/boot/dts/sprd/sp9863a-1h10.dts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/boot/dts/sprd/sp9863a-1h10.dts b/arch/arm64/boot/dts/sprd/sp9863a-1h10.dts
index 2047f7a74265..510f65f4d8b8 100644
--- a/arch/arm64/boot/dts/sprd/sp9863a-1h10.dts
+++ b/arch/arm64/boot/dts/sprd/sp9863a-1h10.dts
@@ -28,7 +28,7 @@
 
 	chosen {
 		stdout-path = "serial1:115200n8";
-		bootargs = "earlycon";
+		bootargs = "earlycon console=ttyS1";
 	};
 };
 
-- 
2.20.1

Re: [RESEND PATCH] arm64: dts: specify console via command line

[Arnd Bergmann]

On Wed, Mar 11, 2020 at 12:21 PM Chunyan Zhang <zhang.lyra@gmail.com> wrote:
>

> diff --git a/arch/arm64/boot/dts/sprd/sp9863a-1h10.dts b/arch/arm64/boot/dts/sprd/sp9863a-1h10.dts
> index 2047f7a74265..510f65f4d8b8 100644
> --- a/arch/arm64/boot/dts/sprd/sp9863a-1h10.dts
> +++ b/arch/arm64/boot/dts/sprd/sp9863a-1h10.dts
> @@ -28,7 +28,7 @@
>
>         chosen {
>                 stdout-path = "serial1:115200n8";
> -               bootargs = "earlycon";
> +               bootargs = "earlycon console=ttyS1";
>         };
>  };

Hi Chunyan,

I would expect that you need to either specify the stdout-path, or the console=
kernel parameter, but not both.

If earlycon was used, shouldn't the driver know which port is the console?

      Arnd

Re: [RESEND PATCH] arm64: dts: specify console via command line

[Chunyan Zhang]

Hi Arnd,

On Wed, 11 Mar 2020 at 22:31, Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Wed, Mar 11, 2020 at 12:21 PM Chunyan Zhang <zhang.lyra@gmail.com> wrote:
> >
>
> > diff --git a/arch/arm64/boot/dts/sprd/sp9863a-1h10.dts b/arch/arm64/boot/dts/sprd/sp9863a-1h10.dts
> > index 2047f7a74265..510f65f4d8b8 100644
> > --- a/arch/arm64/boot/dts/sprd/sp9863a-1h10.dts
> > +++ b/arch/arm64/boot/dts/sprd/sp9863a-1h10.dts
> > @@ -28,7 +28,7 @@
> >
> >         chosen {
> >                 stdout-path = "serial1:115200n8";
> > -               bootargs = "earlycon";
> > +               bootargs = "earlycon console=ttyS1";
> >         };
> >  };
>
> Hi Chunyan,
>
> I would expect that you need to either specify the stdout-path, or the console=
> kernel parameter, but not both.
>

Ok, now I know how to fix the problem without adding 'console=' :)
of_console_check() [1] can tell if a given port is the console by
reading 'stdout-path'.
I will address this issue in serial driver.

Thanks for your reminder,
Chunyan

[1] https://elixir.bootlin.com/linux/v5.6-rc5/source/drivers/of/base.c#L2135

> If earlycon was used, shouldn't the driver know which port is the console?
>
>       Arnd