From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: ptxdist@pengutronix.de
Cc: barebox@lists.infradead.org, d.schultz@phytec.de
Subject: Re: [ptxdist] boot problem w/ barebox
Date: Tue, 12 Sep 2017 10:32:02 +0200 [thread overview]
Message-ID: <20170912083202.urfrvyewzddlghg6@pengutronix.de> (raw)
In-Reply-To: <207dcf09-6116-29e2-e854-aa3e02cc0c10@gr13.net>
Hello,
On Mon, Sep 11, 2017 at 08:47:03PM +0200, Enrico Weigelt, metux IT consult wrote:
> On 11.09.2017 09:16, Uwe Kleine-König wrote:
>
> > Try adding a #define DEBUG in linux-4.13/arch/arm/boot/compressed/head.S
> > > and make sure enabled DEBUG_LL and selected the right UART in your>
> .config.
> After deep digging in the init code, I've meanwhile fixed it (at least
> with self-compiled 2015 bbx - didn't try newer versions yet). In the end
> was just dt misconfiguration (that wasn't obvious in this dts wood,
> which I ported from the old 4.1-phy tree): the debug uart was disabled.
>
> This lead to some funny situations:
>
> * DEBUG_ll worked after fixing the port number (the counting is a bit
> confusing: ttymxc1 is #2)
CONFIG_DEBUG_IMX_UART_PORT=2 means it should use UART-2 as documented in
the reference manual. But yeah, this is confusing, the problem is that
the hardware guy numbering the UARTS named the first UART UART-1 which
isn't what a kernel hacker would have picked.
> * console works up to the point where the uarts tty drivers are
> configured. as the uart was disabled in dt, no tty driver was
> associated (while ll driver was still active), so the clock was
> disabled on some point, leading to supposedly hangup (actually,
> just the console was gone)
When the UART tty driver are configured doesn't play a role here. At
some point during boot all unused clocks are disabled and up to then no
driver ensured your uart clock to be used. And maybe you had a real
hangup because writing to an UART with its clock off might have "funny"
effects.
> * hacking out the clock disable lead further to the point where rootfs
> is mounted and init started
There is no need for a hack, just pass "clk_ignore_unused" on the kernel
command line.
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
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prev parent reply other threads:[~2017-09-12 8:32 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-09 9:01 Enrico Weigelt, metux IT consult
2017-09-11 7:16 ` Uwe Kleine-König
2017-09-11 18:47 ` Enrico Weigelt, metux IT consult
2017-09-12 8:32 ` Uwe Kleine-König [this message]
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