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Subject: Re: applesmc oops in 3.10/3.11
From: Chris Murphy <bugzilla@colorremedies.com>
In-Reply-To: <20131002205931.GA18939@roeck-us.net>
Date: Wed, 2 Oct 2013 15:34:41 -0600
Cc: Henrik Rydberg <rydberg@euromail.se>,
        Josh Boyer <jwboyer@fedoraproject.org>, khali@linux-fr.org,
        lm-sensors@lm-sensors.org,
        "Linux-Kernel@Vger. Kernel. Org" <linux-kernel@vger.kernel.org>
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To: Guenter Roeck <linux@roeck-us.net>
Sender: linux-kernel-owner@vger.kernel.org
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On Oct 2, 2013, at 2:59 PM, Guenter Roeck <linux@roeck-us.net> wrote:

> On Wed, Oct 02, 2013 at 12:33:00PM -0600, Chris Murphy wrote:
>> 
>> On Oct 2, 2013, at 12:02 PM, Guenter Roeck <linux@roeck-us.net> wrote:
>> 
>>> On Wed, Oct 02, 2013 at 07:24:10PM +0200, Henrik Rydberg wrote:
>>>> On Wed, Oct 02, 2013 at 09:47:18AM -0700, Guenter Roeck wrote:
>>>>> On Wed, Oct 02, 2013 at 06:34:18PM +0200, Henrik Rydberg wrote:
>>>>>>>>> One thing I have seen in all logs is the earlier "send_byte fail" message, so
>>>>>>>>> I think that is a pre-requisite.
>>>>>>>> 
>>>>>>>> Not necessarily - it could be that the patch actually fixes the root
>>>>>>>> cause. One possible scenario is that on recent SMCs, some of the
>>>>>>>> commands produce more data than we actually read. This would
>>>>>>>> eventually lead to both data corruption and overflow somwhere in the
>>>>>>>> SMC internals.  If the original SMC error is interpreted as a read
>>>>>>>> buffer overflow, then that problem should be fixed with this patch.
>>>>>>>> 
>>>>>>> 
>>>>>>> Good point.
>>>>>>> 
>>>>>>> But shouldn't we at least get the "flushed %d bytes" warning message in this case ?
>>>>>> 
>>>>>> The explanation I have there is that the (newer) SMC needs the
>>>>>> application to read the 'no more bytes' or it will get confused. It
>>>>>> makes sense, if the number of bytes to read is no longer specified.
>>>>>> 
>>>>> You mean that just reading from APPLESMC_CMD_PORT would solve the problem ?
>>>>> That might make sense.
>>>> 
>>>> It also points at the possibility of a smaller patch to test, but I
>>>> have not had the time to check this very deeply myself:
>>>> 
>>> I like this patch much more than the previous patch. Chris, can you test it ?
>> 
>> Yes. Building now. What kernel message should I be looking for? At least on 2011 and 2012 laptops I have yet to see an Oops related to smc. The kernel with previous patch at least is not causing problems on them so far, which works well as I can test more on the 2008 model.
>> 
> None, if I understand correctly and if the patch really fixes the root cause
> of the problem.

A vast majority of the Ooops I've had are when booting from flash media, testing Fedora installs. Is it possible the much slower kernel load and boot time is a trigger? If so, I'll look into modifying the media to accept the custom kernel and requisite fat initramfs.


Chris--
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