2017-09-19 14:00:32

by Stafford Horne

Subject: [PATCH] openrisc: dts: or1ksim: Add stdout-path

During reviews of the OpenRISC SMP patch series it was suggested to add
stdout-path to the SMP dts file. Add stdout-path to our other dts files
to be a good example.

Signed-off-by: Stafford Horne <[email protected]>
---
arch/openrisc/boot/dts/or1ksim.dts | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/openrisc/boot/dts/or1ksim.dts b/arch/openrisc/boot/dts/or1ksim.dts
index 5d4f9027afaf..ecc30968cbcb 100644
--- a/arch/openrisc/boot/dts/or1ksim.dts
+++ b/arch/openrisc/boot/dts/or1ksim.dts
@@ -7,6 +7,7 @@

chosen {
bootargs = "console=uart,mmio,0x90000000,115200";
+ stdout-path = &serial0;
};

memory@0 {
--
2.13.5

2017-09-19 16:49:51

by Geert Uytterhoeven

Subject: Re: [PATCH] openrisc: dts: or1ksim: Add stdout-path

Hi Stafford,

On Tue, Sep 19, 2017 at 4:00 PM, Stafford Horne <[email protected]> wrote:
> During reviews of the OpenRISC SMP patch series it was suggested to add
> stdout-path to the SMP dts file. Add stdout-path to our other dts files
> to be a good example.
>
> Signed-off-by: Stafford Horne <[email protected]>
> ---
> arch/openrisc/boot/dts/or1ksim.dts | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/openrisc/boot/dts/or1ksim.dts b/arch/openrisc/boot/dts/or1ksim.dts
> index 5d4f9027afaf..ecc30968cbcb 100644
> --- a/arch/openrisc/boot/dts/or1ksim.dts
> +++ b/arch/openrisc/boot/dts/or1ksim.dts
> @@ -7,6 +7,7 @@
>
> chosen {
> bootargs = "console=uart,mmio,0x90000000,115200";
> + stdout-path = &serial0;

I think that should be:

- bootargs = "console=uart,mmio,0x90000000,115200";
+ stdout-path = "serial0:115200";

If stdout-path is present, it will become the default console.
All other UART parameters except for the serial speed are derived from
the serial0 node (= serial@90000000) in DT.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

2017-09-20 14:04:47

by Stafford Horne

Subject: Re: [PATCH] openrisc: dts: or1ksim: Add stdout-path

Hi Geert,

On Tue, Sep 19, 2017 at 06:49:48PM +0200, Geert Uytterhoeven wrote:
> Hi Stafford,
>
> On Tue, Sep 19, 2017 at 4:00 PM, Stafford Horne <[email protected]> wrote:
> > During reviews of the OpenRISC SMP patch series it was suggested to add
> > stdout-path to the SMP dts file. Add stdout-path to our other dts files
> > to be a good example.
> >
> > Signed-off-by: Stafford Horne <[email protected]>
> > ---
> > arch/openrisc/boot/dts/or1ksim.dts | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/openrisc/boot/dts/or1ksim.dts b/arch/openrisc/boot/dts/or1ksim.dts
> > index 5d4f9027afaf..ecc30968cbcb 100644
> > --- a/arch/openrisc/boot/dts/or1ksim.dts
> > +++ b/arch/openrisc/boot/dts/or1ksim.dts
> > @@ -7,6 +7,7 @@
> >
> > chosen {
> > bootargs = "console=uart,mmio,0x90000000,115200";
> > + stdout-path = &serial0;
>
> I think that should be:
>
> - bootargs = "console=uart,mmio,0x90000000,115200";
> + stdout-path = "serial0:115200";
>
> If stdout-path is present, it will become the default console.
> All other UART parameters except for the serial speed are derived from
> the serial0 node (= serial@90000000) in DT.

Thanks for the tip. I have seen examples using alias `&serial0;` and using
the name directly `serio0:115200', but I guess I didnt really understand
what was going on. I read through as much of the console initialization,
of, earlycon and printk code as I needed to refresh my memory on this...

It seems there are a few other issues here:
- To use "serial0:115200" we will need an alias to the path (or specify
the full path)
- It looks like we can't use console= and stdout-path at the same time
- We still need "earlycon" to define that we want to initialize early
printk

I think updating to something like the below works, but its a few extra
lines:


diff --git a/arch/openrisc/boot/dts/or1ksim.dts b/arch/openrisc/boot/dts/or1ksim.dts
index ecc30968cbcb..37779a45947c 100644
--- a/arch/openrisc/boot/dts/or1ksim.dts
+++ b/arch/openrisc/boot/dts/or1ksim.dts
@@ -5,9 +5,13 @@
#size-cells = <1>;
interrupt-parent = <&pic>;

+ aliases {
+ uart0 = &serial0;
+ };
+
chosen {
- bootargs = "console=uart,mmio,0x90000000,115200";
- stdout-path = &serial0;
+ bootargs = "earlycon";
+ stdout-path = "uart0:115200";
};

memory@0 {


The boot prompt before showed:

Kernel command line: console=uart,mmio,0x90000000,115200
earlycon: uart0 at MMIO 0x90000000 (options '115200')
bootconsole [uart0] enabled

Now it shows:

Kernel command line: earlycon
earlycon: ns16550a0 at MMIO 0x90000000 (options '115200')
bootconsole [ns16550a0] enabled

-Stafford