[PATCH 0/3] ARM: dts: Define stdout-patch for Exynos Chromebooks

[PATCH 0/3] ARM: dts: Define stdout-patch for Exynos Chromebooks

[Javier Martinez Canillas]

The kernel can use as the default console a serial port if is defined
as stdout device in the Device Tree.
    
This allows a board to be booted without the need of having a console
parameter in the kernel command line.

This small series add a stdout-path property for Exynos5 Chromebooks and
is composed of the following patches:

Javier Martinez Canillas (3):
  ARM: dts: Define stdout-path property for Peach boards
  ARM: dts: Define stdout-path property for Snow board
  ARM: dts: Define stdout-path property for Spring board

 arch/arm/boot/dts/exynos5250-snow.dts      | 1 +
 arch/arm/boot/dts/exynos5250-spring.dts    | 1 +
 arch/arm/boot/dts/exynos5420-peach-pit.dts | 4 ++++
 arch/arm/boot/dts/exynos5800-peach-pi.dts  | 4 ++++
 4 files changed, 10 insertions(+)

Best regards,
Javier

[PATCH 1/3] ARM: dts: Define stdout-path property for Peach boards

[Javier Martinez Canillas]

The kernel can use as the default console a serial port if is defined
as stdout device in the Device Tree.

This allows a board to be booted without the need of having a console
parameter in the kernel command line.

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
---
 arch/arm/boot/dts/exynos5420-peach-pit.dts | 4 ++++
 arch/arm/boot/dts/exynos5800-peach-pi.dts  | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/arch/arm/boot/dts/exynos5420-peach-pit.dts b/arch/arm/boot/dts/exynos5420-peach-pit.dts
index d0ee55f4d09f..3f4e2feaa927 100644
--- a/arch/arm/boot/dts/exynos5420-peach-pit.dts
+++ b/arch/arm/boot/dts/exynos5420-peach-pit.dts
@@ -43,6 +43,10 @@
 		pinctrl-names = "default";
 	};
 
+	chosen {
+		stdout-path = "serial3:115200n8";
+	};
+
 	fixed-rate-clocks {
 		oscclk {
 			compatible = "samsung,exynos5420-oscclk";
diff --git a/arch/arm/boot/dts/exynos5800-peach-pi.dts b/arch/arm/boot/dts/exynos5800-peach-pi.dts
index 7ea1d66dd719..c833bacf873b 100644
--- a/arch/arm/boot/dts/exynos5800-peach-pi.dts
+++ b/arch/arm/boot/dts/exynos5800-peach-pi.dts
@@ -42,6 +42,10 @@
 		pinctrl-names = "default";
 	};
 
+	chosen {
+		stdout-path = "serial3:115200n8";
+	};
+
 	fixed-rate-clocks {
 		oscclk {
 			compatible = "samsung,exynos5420-oscclk";
-- 
2.1.4

[PATCH 2/3] ARM: dts: Define stdout-path property for Snow board

[Javier Martinez Canillas]

The kernel can use as the default console a serial port if is defined
as stdout device in the Device Tree.

This allows a board to be booted without the need of having a console
parameter in the kernel command line.

Currently the Snow DTS has a bootargs in the /chosen node and this is
kept since users that don't have a serial console on this board might
be using it to have the boot log shown in the display. This will have
more precedence than the stdout-path but it's fine since is only used
when CONFIG_ARM_ATAG_DTB_COMPAT_CMDLINE_EXTEND is enabled.

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
---
 arch/arm/boot/dts/exynos5250-snow.dts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/boot/dts/exynos5250-snow.dts b/arch/arm/boot/dts/exynos5250-snow.dts
index 5be966df7603..2657e842e5a5 100644
--- a/arch/arm/boot/dts/exynos5250-snow.dts
+++ b/arch/arm/boot/dts/exynos5250-snow.dts
@@ -29,6 +29,7 @@
 
 	chosen {
 		bootargs = "console=tty1";
+		stdout-path = "serial3:115200n8";
 	};
 
 	gpio-keys {
-- 
2.1.4

[PATCH 3/3] ARM: dts: Define stdout-path property for Spring board

[Javier Martinez Canillas]

The kernel can use as the default console a serial port if is defined
as stdout device in the Device Tree.

This allows a board to be booted without the need of having a console
parameter in the kernel command line.

Currently the Spring DTS has bootargs in the /chosen node and this is
kept since users that don't have a serial console on this board might
be using it to have the boot log shown in the display. This will have
more precedence than the stdout-path but it's fine since is only used
when CONFIG_ARM_ATAG_DTB_COMPAT_CMDLINE_EXTEND is enabled.

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
---
 arch/arm/boot/dts/exynos5250-spring.dts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/boot/dts/exynos5250-spring.dts b/arch/arm/boot/dts/exynos5250-spring.dts
index f02775487cd4..b9ec763a5602 100644
--- a/arch/arm/boot/dts/exynos5250-spring.dts
+++ b/arch/arm/boot/dts/exynos5250-spring.dts
@@ -25,6 +25,7 @@
 
 	chosen {
 		bootargs = "console=tty1";
+		stdout-path = "serial3:115200n8";
 	};
 
 	gpio-keys {
-- 
2.1.4

[PATCH 3/3] ARM: dts: Define stdout-path property for Spring board

[Andreas Färber]

Hi,

Am 16.03.2015 um 11:28 schrieb Javier Martinez Canillas:
> The kernel can use as the default console a serial port if is defined

"The kernel can use a serial port as the default console if it's defined
..."

> as stdout device in the Device Tree.
> 
> This allows a board to be booted without the need of having a console
> parameter in the kernel command line.
> 
> Currently the Spring DTS has bootargs in the /chosen node and this is
> kept since users that don't have a serial console on this board might
> be using it to have the boot log shown in the display. This will have
> more precedence than the stdout-path but it's fine since is only used

"since it's"

> when CONFIG_ARM_ATAG_DTB_COMPAT_CMDLINE_EXTEND is enabled.
> 
> Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
> ---
>  arch/arm/boot/dts/exynos5250-spring.dts | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm/boot/dts/exynos5250-spring.dts b/arch/arm/boot/dts/exynos5250-spring.dts
> index f02775487cd4..b9ec763a5602 100644
> --- a/arch/arm/boot/dts/exynos5250-spring.dts
> +++ b/arch/arm/boot/dts/exynos5250-spring.dts
> @@ -25,6 +25,7 @@
>  
>  	chosen {
>  		bootargs = "console=tty1";
> +		stdout-path = "serial3:115200n8";

Is this a guess or did you verify that against some schematics?

>  	};
>  
>  	gpio-keys {

Assuming that bootargs still work,

Reviewed-by: Andreas F?rber <afaerber@suse.de>

I do wonder why this mechanism could not point to the same location as
bootargs? ("dp-controller"?) The device does not even have screws for
opening it, so accessing the serial port is highly theoretical.

Regards,
Andreas

-- 
SUSE Linux GmbH, Maxfeldstr. 5, 90409 N?rnberg, Germany
GF: Felix Imend?rffer, Jane Smithard, Jennifer Guild, Dilip Upmanyu,
Graham Norton; HRB 21284 (AG N?rnberg)

[PATCH 3/3] ARM: dts: Define stdout-path property for Spring board

[Javier Martinez Canillas]

Hello Andreas,

>> index f02775487cd4..b9ec763a5602 100644
>> --- a/arch/arm/boot/dts/exynos5250-spring.dts
>> +++ b/arch/arm/boot/dts/exynos5250-spring.dts
>> @@ -25,6 +25,7 @@
>>
>>       chosen {
>>               bootargs = "console=tty1";
>> +             stdout-path = "serial3:115200n8";
>
> Is this a guess or did you verify that against some schematics?
>

I don't have access to the Spring schematics but it is based on what
is defined in the vendor u-boot for Spring [0].

There isn't a Spring specific configuration file but only a
chromeos_daisy.h which is shared by Snow, Spring and Kate (not yet in
mainline):

#define CONFIG_DIRECT_BOOTARGS \
"console=ttySAC3," STRINGIFY(CONFIG_BAUDRATE) " debug earlyprintk"

So I assumed that all daisy-based Chromebooks use the same UART for debug.

>>       };
>>
>>       gpio-keys {
>
> Assuming that bootargs still work,
>

Yes, the semantics are not changed. The std-out property is only used
as a default if no console= parameter is passed so if you already are
passing one in your bootloader or using the one defined in the /chosen
bootargs by enabling CONFIG_ARM_ATAG_DTB_COMPAT_CMDLINE_EXTEND, that
will be used instead of std-out.

> Reviewed-by: Andreas F?rber <afaerber@suse.de>
>
> I do wonder why this mechanism could not point to the same location as
> bootargs? ("dp-controller"?) The device does not even have screws for

I did wonder the same indeed but I don't know if you can use a display
as std-out or only works for serial consoles.

> opening it, so accessing the serial port is highly theoretical.
>

I see, in that case I think we could just drop this patch if is not
possible to have a serial console even with some soldering like is the
case in Snow, Peach Pit and Peach Pi.

> Regards,
> Andreas
>

Best regards,
Javier

[0]: https://chromium.googlesource.com/chromiumos/third_party/u-boot/+/firmware-spring-3824.B/include/configs/chromeos_daisy.h

[PATCH 3/3] ARM: dts: Define stdout-path property for Spring board

[Kukjin Kim]

On 03/16/15 20:28, Javier Martinez Canillas wrote:
> Hello Andreas,
> 
Hi,

>>> index f02775487cd4..b9ec763a5602 100644
>>> --- a/arch/arm/boot/dts/exynos5250-spring.dts
>>> +++ b/arch/arm/boot/dts/exynos5250-spring.dts
>>> @@ -25,6 +25,7 @@
>>>
>>>       chosen {
>>>               bootargs = "console=tty1";
>>> +             stdout-path = "serial3:115200n8";
>>
>> Is this a guess or did you verify that against some schematics?
>>
> 
> I don't have access to the Spring schematics but it is based on what
> is defined in the vendor u-boot for Spring [0].
> 
> There isn't a Spring specific configuration file but only a
> chromeos_daisy.h which is shared by Snow, Spring and Kate (not yet in
> mainline):
> 
> #define CONFIG_DIRECT_BOOTARGS \
> "console=ttySAC3," STRINGIFY(CONFIG_BAUDRATE) " debug earlyprintk"
> 
> So I assumed that all daisy-based Chromebooks use the same UART for debug.
> 
>>>       };
>>>
>>>       gpio-keys {
>>
>> Assuming that bootargs still work,
>>
> 
> Yes, the semantics are not changed. The std-out property is only used
> as a default if no console= parameter is passed so if you already are
> passing one in your bootloader or using the one defined in the /chosen
> bootargs by enabling CONFIG_ARM_ATAG_DTB_COMPAT_CMDLINE_EXTEND, that
> will be used instead of std-out.
> 
>> Reviewed-by: Andreas F?rber <afaerber@suse.de>
>>
>> I do wonder why this mechanism could not point to the same location as
>> bootargs? ("dp-controller"?) The device does not even have screws for
> 
> I did wonder the same indeed but I don't know if you can use a display
> as std-out or only works for serial consoles.
> 
>> opening it, so accessing the serial port is highly theoretical.
>>
> 
> I see, in that case I think we could just drop this patch if is not
> possible to have a serial console even with some soldering like is the
> case in Snow, Peach Pit and Peach Pi.
> 
I've applied this whole series so if you guys find any problem on this,
please let me know ;)

Thanks,
Kukjin

[PATCH 0/3] ARM: dts: Define stdout-patch for Exynos Chromebooks

[Kukjin Kim]

Javier Martinez Canillas wrote:
> 
> The kernel can use as the default console a serial port if is defined
> as stdout device in the Device Tree.
> 
> This allows a board to be booted without the need of having a console
> parameter in the kernel command line.
> 
> This small series add a stdout-path property for Exynos5 Chromebooks and
> is composed of the following patches:
> 
> Javier Martinez Canillas (3):
>   ARM: dts: Define stdout-path property for Peach boards
>   ARM: dts: Define stdout-path property for Snow board
>   ARM: dts: Define stdout-path property for Spring board
> 
>  arch/arm/boot/dts/exynos5250-snow.dts      | 1 +
>  arch/arm/boot/dts/exynos5250-spring.dts    | 1 +
>  arch/arm/boot/dts/exynos5420-peach-pit.dts | 4 ++++
>  arch/arm/boot/dts/exynos5800-peach-pi.dts  | 4 ++++
>  4 files changed, 10 insertions(+)
> 
+ Arnd

Basically, I have no objection to add stdout-path property on board DT but I
need to ask other ARM guys how they think about? Always I'm questioned what
should be defined in bootloader before entering kernel and IMHO kernel can do
it, it should be defined in bootloader though ;)

Let's wait for other opinions...

Thanks,
Kukjin

[PATCH 0/3] ARM: dts: Define stdout-patch for Exynos Chromebooks

[Arnd Bergmann]

On Tuesday 17 March 2015 10:51:13 Kukjin Kim wrote:
> Javier Martinez Canillas wrote:
> > 
> > The kernel can use as the default console a serial port if is defined
> > as stdout device in the Device Tree.
> > 
> > This allows a board to be booted without the need of having a console
> > parameter in the kernel command line.
> > 
> > This small series add a stdout-path property for Exynos5 Chromebooks and
> > is composed of the following patches:
> > 
> > Javier Martinez Canillas (3):
> >   ARM: dts: Define stdout-path property for Peach boards
> >   ARM: dts: Define stdout-path property for Snow board
> >   ARM: dts: Define stdout-path property for Spring board
> > 
> >  arch/arm/boot/dts/exynos5250-snow.dts      | 1 +
> >  arch/arm/boot/dts/exynos5250-spring.dts    | 1 +
> >  arch/arm/boot/dts/exynos5420-peach-pit.dts | 4 ++++
> >  arch/arm/boot/dts/exynos5800-peach-pi.dts  | 4 ++++
> >  4 files changed, 10 insertions(+)
> > 
> + Arnd
> 
> Basically, I have no objection to add stdout-path property on board DT but I
> need to ask other ARM guys how they think about? Always I'm questioned what
> should be defined in bootloader before entering kernel and IMHO kernel can do
> it, it should be defined in bootloader though 
> 
> Let's wait for other opinions...
> 

We're trying to do this on all machines now so we can replace
debug_ll with earlycon for any normal use case aside from early
early boot debugging.

Please merge this patch set.

	Arnd

[PATCH 0/3] ARM: dts: Define stdout-patch for Exynos Chromebooks

[Kukjin Kim]

On 03/17/15 14:27, Arnd Bergmann wrote:
> On Tuesday 17 March 2015 10:51:13 Kukjin Kim wrote:
>> Javier Martinez Canillas wrote:
>>>
>>> The kernel can use as the default console a serial port if is defined
>>> as stdout device in the Device Tree.
>>>
>>> This allows a board to be booted without the need of having a console
>>> parameter in the kernel command line.
>>>
>>> This small series add a stdout-path property for Exynos5 Chromebooks and
>>> is composed of the following patches:
>>>
>>> Javier Martinez Canillas (3):
>>>   ARM: dts: Define stdout-path property for Peach boards
>>>   ARM: dts: Define stdout-path property for Snow board
>>>   ARM: dts: Define stdout-path property for Spring board
>>>
>>>  arch/arm/boot/dts/exynos5250-snow.dts      | 1 +
>>>  arch/arm/boot/dts/exynos5250-spring.dts    | 1 +
>>>  arch/arm/boot/dts/exynos5420-peach-pit.dts | 4 ++++
>>>  arch/arm/boot/dts/exynos5800-peach-pi.dts  | 4 ++++
>>>  4 files changed, 10 insertions(+)
>>>
>> + Arnd
>>
>> Basically, I have no objection to add stdout-path property on board DT but I
>> need to ask other ARM guys how they think about? Always I'm questioned what
>> should be defined in bootloader before entering kernel and IMHO kernel can do
>> it, it should be defined in bootloader though 
>>
>> Let's wait for other opinions...
>>
> 
> We're trying to do this on all machines now so we can replace
> debug_ll with earlycon for any normal use case aside from early
> early boot debugging.
> 
> Please merge this patch set.
> 
OK, got it. Applied.

Thanks,
Kukjin