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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CABxcv=mmr-WWXY7-KUJe-3EP8FHRBzv-SabJma9VwGRPiHio3Q@mail.gmail.com>
Date:	Mon, 16 Mar 2015 12:28:42 +0100
From:	Javier Martinez Canillas <javier@...hile0.org>
To:	Andreas Färber <afaerber@...e.de>
Cc:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	Kukjin Kim <kgene@...nel.org>, Olof Johansson <olof@...om.net>,
	Doug Anderson <dianders@...omium.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] ARM: dts: Define stdout-path property for Spring board

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 Färber <afaerber@...e.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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/