linux-kernel - Re: [PATCH v2 3/7] tty/serial: convert 8250 to generic earlycon

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Message-ID: <CA+8MBbLooWm9xys+gYa5uL1eVTH-qzaR+RaZgsrqV-8XkqGadQ@mail.gmail.com>
Date:	Tue, 10 Jun 2014 13:52:08 -0700
From:	Tony Luck <tony.luck@...il.com>
To:	Rob Herring <robherring2@...il.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Yinghai Lu <yinghai@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	Jiri Slaby <jslaby@...e.cz>,
	Catalin Marinas <catalin.marinas@....com>,
	Russell King <linux@....linux.org.uk>,
	Will Deacon <will.deacon@....com>,
	Arnd Bergmann <arnd@...db.de>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 3/7] tty/serial: convert 8250 to generic earlycon

On Mon, Jun 9, 2014 at 4:18 PM, Rob Herring <robherring2@...il.com> wrote:
> It should do auto detect of the baud-rate if it is not specified which
> for 8250 is just reading the baud-rate divider and calculating the
> baud-rate using the uart clock. It should just reprogram the divider
> with the same divider value. I don't see anything obvious why this
> would have broken.

Something very weird is happening.  Output is good so long as I put the
trailing ",115200" on the command line.

But I made early_serial8250_setup() printk() the return value it got
from probe_baud() - in case is was somehow getting 115201 or some
other silly value ... nope. Exactly 115200.

I also can't explain why the "noise" comes and goes a dozen
times during boot,

Does some other place in the kernel look at the "uart..." command
line argument?

-Tony
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