From mboxrd@z Thu Jan  1 00:00:00 1970
From: Lucas Stach <l.stach@pengutronix.de>
Subject: Re: [PATCH] Revert "serial: imx: remove unbalanced clk_prepare"
Date: Mon, 28 Sep 2015 10:15:30 +0200
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References: <1439912592-14779-1-git-send-email-fabio.estevam@freescale.com>
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To: Fabio Estevam <festevam@gmail.com>
Cc: Fabio Estevam <fabio.estevam@freescale.com>, Sascha Hauer <kernel@pengutronix.de>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Eduardo Valentin <edubezval@gmail.com>, "linux-serial@vger.kernel.org" <linux-serial@vger.kernel.org>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>
List-Id: linux-serial@vger.kernel.org

Am Samstag, den 26.09.2015, 17:14 -0300 schrieb Fabio Estevam:
> Hi Greg,
> 
> On Tue, Aug 18, 2015 at 12:43 PM, Fabio Estevam
> <fabio.estevam@freescale.com> wrote:
> > This reverts commit 9e7b399d6528eac33a6fbfceb2b92af209c3454d.
> >
> > Commit ("9e7b399d6528ea") causes the following warning and sometimes
> > also hangs the system:
> >
> > ------------[ cut here ]------------
> >  WARNING: CPU: 0 PID: 0 at kernel/locking/mutex.c:868 mutex_trylock+0x20c/0x22c()
> >  DEBUG_LOCKS_WARN_ON(in_interrupt())
> >  Modules linked in:
> > CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.2.0-rc7-next-20150818-00001-g14418a6 #4
> > Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
> > Backtrace:
> > [<80012f08>] (dump_backtrace) from [<800130a4>] (show_stack+0x18/0x1c)
> > r6:00000364 r5:00000000 r4:00000000 r3:00000000
> > [<8001308c>] (show_stack) from [<807902b8>] (dump_stack+0x88/0xa4)
> > [<80790230>] (dump_stack) from [<8002a604>] (warn_slowpath_common+0x80/0xbc)
> > r5:807945c4 r4:80ab3b50
> > [<8002a584>] (warn_slowpath_common) from [<8002a6e4>] (warn_slowpath_fmt+0x38/0x40)
> > r8:00000000 r7:8131100c r6:8054c3cc r5:8131300c r4:80b0a570
> > [<8002a6b0>] (warn_slowpath_fmt) from [<807945c4>] (mutex_trylock+0x20c/0x22c)
> > r3:8095d0d8 r2:8095ab28
> > [<807943b8>] (mutex_trylock) from [<8054c3cc>] (clk_prepare_lock+0x14/0xf4)
> > r7:8131100c r6:be3f0c80 r5:00000037 r4:be3f0c80
> > [<8054c3b8>] (clk_prepare_lock) from [<8054dbfc>] (clk_prepare+0x18/0x30)
> > r5:00000037 r4:be3f0c80
> > [<8054dbe4>] (clk_prepare) from [<8036a600>] (imx_console_write+0x30/0x244)
> > r4:812d0bc8 r3:8132b9a4
> >
> > To reproduce the problem we only need to let the board idle for something
> > like 30 seconds.
> >
> > Tested on a imx6q-sabresd.
> >
> > Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
> 
> Could you please consider applying this one for 4.3-rc?
> 
To put a bit more wight behind this: without this revert i.MX6 with an
active serial console boards are not even able to boot into userspace.

Please apply this as a critical fix.

Regards,
Lucas
-- 
Pengutronix e.K.             | Lucas Stach                 |
Industrial Linux Solutions   | http://www.pengutronix.de/  |