From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: Question about arm64 earlycon
Date: Mon, 24 Oct 2016 12:06:29 +0200 [thread overview]
Message-ID: <4966376.bRx4fgSjbT@wuerfel> (raw)
In-Reply-To: <CADaLNDnB3QBjODYNTndBsexGQfnL1rj6DAUPcf1nT9+aJaqCtw@mail.gmail.com>
On Sunday, October 23, 2016 12:26:59 AM CEST Duc Dang wrote:
> Hi Catalin, Marc, Mark, Arnd,
>
> I am testing with 3.12 kernel with earlyprintk enabled and I see some
> garbage characters in the console log right before the message
> indicating that the real console device is initialized:
>
> <some garbage characters here>01c020000.serial: ttyS0 at MMIO
> 0x1c020000 (irq = 108, base_baud = 3125000) is a U6_16550A
> console [ttyS0] enabled, bootconsole disabled
>
> I looked through early_prink.c file and printk.c file and it looks
> like there is case that some early boot code can touch the UART
> hardware via ealy console driver while the 'real' console driver is
> setting up the same UART port? Please let me know if I missed some
> important piece of code that can prevent this.
I don't think we every supported earlyprintk on arm64, and
earlycon support may have been added later.
If you can't use a modern kernel, try backporting all the
relevant earlycon changes.
Arnd
next prev parent reply other threads:[~2016-10-24 10:06 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-23 7:26 Question about arm64 earlycon Duc Dang
2016-10-24 10:06 ` Arnd Bergmann [this message]
2016-10-24 10:17 ` Marc Zyngier
2016-10-24 11:09 ` Mark Rutland
2016-10-24 17:24 ` Duc Dang
2016-10-24 18:03 ` Mark Rutland
2016-10-24 17:29 ` Duc Dang
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