linux-kernel - Re: [GIT PULL 1/2] bcm2835-dt-fixes-2017-10-06

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Message-ID: <CAJsfgeVGhqeXc++zjxXg7csXhHHNVmbbc69RfyhUSVHXc60HCQ@mail.gmail.com>
Date:   Thu, 2 Nov 2017 08:33:17 +0000
From:   Matt Hart <matt@...tface.org>
To:     Stefan Wahren <stefan.wahren@...e.com>
Cc:     Peter Robinson <pbrobinson@...il.com>,
        Marcel Holtmann <marcel@...tmann.org>,
        Eric Anholt <eric@...olt.net>, linux-kernel@...r.kernel.org,
        bcm-kernel-feedback-list@...adcom.com,
        Loic Poulain <loic.poulain@...il.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-rpi-kernel@...ts.infradead.org
Subject: Re: [GIT PULL 1/2] bcm2835-dt-fixes-2017-10-06

On 1 November 2017 at 17:44, Stefan Wahren <stefan.wahren@...e.com> wrote:
> Hi Matt,
>
>> Matt Hart <matt@...tface.org> hat am 1. November 2017 um 14:06 geschrieben:
>>
>>
>> On 1 November 2017 at 12:05, Stefan Wahren <stefan.wahren@...e.com> wrote:
>> > Hi Matt, hi Peter,
>> >
>> > Am 01.11.2017 um 10:37 schrieb Peter Robinson:
>> >> On Tue, Oct 31, 2017 at 5:00 PM, Matt Hart <matt@...tface.org> wrote:
>> >>> On 6 October 2017 at 23:14, Florian Fainelli <f.fainelli@...il.com> wrote:
>> >>>> On 10/06/2017 03:05 PM, Eric Anholt wrote:
>> >>>>> Hi Florian.  Here's a patch that's gone through a couple of revisions
>> >>>>> on the list, that seriously fixes up the default serial behavior --
>> >>>>> previously, without the right config.txt/cmdline bits, you'd often end
>> >>>>> up with a hang with no output before booting completed.  It would be
>> >>>>> great to get it into 4.14.
>> >>>>>
>> >>>>> The following changes since commit 2bd6bf03f4c1c59381d62c61d03f6cc3fe71f66e:
>> >>>>>
>> >>>>>   Linux 4.14-rc1 (2017-09-16 15:47:51 -0700)
>> >>>>>
>> >>>>> are available in the git repository at:
>> >>>>>
>> >>>>>   git://github.com/anholt/linux tags/bcm2835-dt-fixes-2017-10-06
>> >>>>>
>> >>>>> for you to fetch changes up to f08f58a2bf68900a84e782b8c7ad701c0654173c:
>> >>>>>
>> >>>>>   ARM: dts: bcm283x: Fix console path on RPi3 (2017-10-06 13:04:56 -0700)
>> >>>>>
>> >>>>> ----------------------------------------------------------------
>> >>>>> This pull request brings in a fix for default serial console setup on
>> >>>>> RPi3, so it now comes up with no config.txt/cmdline.txt settings in
>> >>>>> the firmware.
>> >>>>>
>> >>>>> ----------------------------------------------------------------
>> >>>> Merged, thanks Eric
>> >>>>
>> >>>> --
>> >>>> Florian
>> >>> Hi all,
>> >>>
>> >>> I realise this patch has been in mainline for a more than a week, but
>> >>> I've only recently had time to bisect broken rpi-3 boots in kernelci
>> >>> and found f08f58a2bf68900a84e782b8c7ad701c0654173c as the cause.
>> >>>
>> >>> Kernelci boots the rpi3 using uboot, with console=ttyS0 in the command
>> >>> line which now fails:
>> >>> https://kernelci.org/boot/id/59f787f059b5147794ef1dcf/
>> >>>
>> >>> Is there an alias I can use for both before and after this patch?
>> >>>
>> >>> Mainline boots fine if I use console=ttyS1 or drop the console arg
>> >>> altogether, but as we don't currently support different boot args per
>> >>> tree, and we don't have the manpower to track this patch in all the
>> >>> trees we test, we will have to switch to only boot testing mainline
>> >>> from now on.
>> >> Yes, I've seen the same in Fedora with that patch.
>> >>
>> >>
>> > could you please describe the issue more in detail.
>> >
>> > Does u-boot or Linux hang? Does u-boot select the wrong UART? Is there a
>> > pinmux conflict?
>> Linux throws a kernel panic, "Warning: unable to open an initial console."
>
> what happens if you specify both?
>
> console=ttyS0,115200n8 console=ttyS1,115200n8

You can't do that, as per
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/admin-guide/serial-console.rst#n45

I tried it anyway, and new kernel with this patch failed with the same
error, I suspect it used the first console definition on the command
line.

Incidentally, on the old pre-patch kernel, it did boot to a prompt but
I got double kernel output as it setup 2 consoles both on ttyS0.
https://pastebin.com/raw/Uf09gUaP

I think Eric is right here, it was just wrong before and we'll have to
live with the legacy.

-- 
Matt Hart