From: Felipe Balbi <balbi@ti.com>
To: John Stultz <john.stultz@linaro.org>
Cc: Felipe Balbi <balbi@ti.com>, Greg Kroah-Hartman <gregkh@suse.de>,
lkml <linux-kernel@vger.kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
Nicolas Pitre <nicolas.pitre@linaro.org>
Subject: Re: [RFC][PATCH] musb: Avoid musb_gadget_pullup "Unhandled fault" oops on omap4
Date: Fri, 29 Jul 2011 08:04:38 +0300 [thread overview]
Message-ID: <20110729050437.GB9069@legolas.emea.dhcp.ti.com> (raw)
In-Reply-To: <1311206974.2945.198.camel@work-vm>
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hi,
On Wed, Jul 20, 2011 at 05:09:34PM -0700, John Stultz wrote:
> I've recently run across an "Unhandled fault: imprecise external abort"
> oops that is caused when a driver called usb_gadget_connect() when there
> was no cable plugged into the musb gadget port.
>
> You can see the oops message here:
> https://launchpadlibrarian.net/75635123/minicom.txt
>
> Doing some digging, it seemed the problem was triggered when reading
> from the musb registers in musb_pullup() when the device controller is
> powered down.
>
> Looking at other examples of where the registers were accessed, I
> noticed they were always enclosed by pm_runtime_get/put calls. So I
> added such calls to the musb_gadget_pullup() function and it seemed to
> resolve the problem.
>
> Now, full disclosure: this was triggered with the out-of-tree Android
> adb gadget driver. However, I suspect the same behavior could be
> triggered using the composite gadget driver as well, so I think this is
> a generic issue. However, if I'm wrong, let me know and I'll try to make
> sure the fix is done in the right place.
>
> If this is the right fix, it probably should be queued for 3.1 and
> 3.0-stable.
>
> Comments and feedback would be greatly appreciated!
>
>
> Reported-by: Zach Pfeffer <zach.pfeffer@linaro.org>
> Signed-off-by: John Stultz <john.stultz@linaro.org>
Applied, thanks.
improved commit log slightly:
commit 7e1bb0fdcc9b51ebec0a1e5e06ff075aab55c941
Author: John Stultz <john.stultz@linaro.org>
Date: Wed Jul 20 17:09:34 2011 -0700
usb: musb: fix oops on musb_gadget_pullup
an 'unhandled fault' is causes when a gadget driver calls
usb_gadget_connect() while the USB cable isn't plugged into
the OTG port.
the fault is caused by an access to MUSB's memory space
while its clock is turned off due to pm_runtime kicking
in.
in order to fix the fault, we enclose musb_gadget_pullup()
with pm_runtime_get_sync() ... pm_runtime_put() calls to
be sure we will always reach that path with clock turned on.
[ balbi@ti.com : simplified commit log; removed few things
which didn't belong there ]
Cc: stable@kernel.org
Reported-by: Zach Pfeffer <zach.pfeffer@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>
--
balbi
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next prev parent reply other threads:[~2011-07-29 5:04 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-21 0:09 [RFC][PATCH] musb: Avoid musb_gadget_pullup "Unhandled fault" oops on omap4 John Stultz
2011-07-25 15:43 ` john stultz
2011-07-25 17:27 ` Felipe Balbi
2011-07-27 19:15 ` Felipe Balbi
2011-07-29 5:04 ` Felipe Balbi [this message]
2011-08-03 23:14 ` Colin Cross
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