Commit f5d9b7f0f9 (fix r600_enable_sclk_control()) causes kexec issues

[Eric W. Biederman]

Alex Deucher <alexdeucher at gmail.com> writes:

> On Mon, Jul 29, 2013 at 11:50 AM, Eric W. Biederman
> <ebiederm at xmission.com> wrote:
>>
>>
>> Alex Deucher <alexdeucher at gmail.com> wrote:
>>>On Mon, Jul 29, 2013 at 10:09 AM, Markus Trippelsdorf
>>><markus at trippelsdorf.de> wrote:
>>>> On 2013.07.29 at 09:58 -0400, Alex Deucher wrote:
>>>>> On Mon, Jul 29, 2013 at 3:51 AM, Markus Trippelsdorf
>>>>> <markus at trippelsdorf.de> wrote:
>>>>> > On my test machine Xorg doesn't start anymore when I kexec into a
>>>>> > 3.11.0-rc3 kernel.
>>>>>
>>>>> With kexec, dpm doesn't get torn down properly which can result in a
>>>>> bad hardware state when the driver loads again.  Does the attached
>>>>> patch help?  It attempts to disable dpm at startup in case it wasn't
>>>>> torn down properly previously.
>>>>
>>>> dpm initialization now works, but unfortunately GPU acceleration
>>>still gets
>>>> disabled:
>>>
>>>Stupid kexec complicates things.  We need to make sure dpm is torn
>>>down before we init the rest of the GPU, but dpm needs get initialized
>>>later in the init process since it depends on certain other state from
>>>the driver.  I need to think about this for a bit.  I'm not sure of a
>>>good way to handle this.
>>
>> You might just want to implement a shutdown method that cleans things up properly.   At least as a first pass until you worry about things like kexec on panic.
>>
>> Or can you not shutdown the graphics stack on reboot because of the need to display the kernels shutdown progress?
>
> Does kexec actually call this shutdown method?  The driver implements
> appropriate clean-up measures if it's shutdown properly.

Absoltuely.  All parts of the reboot path call ->shutdown.  Including
kexec.

You don't get a device remove/hotunplug but unless this is a kexec on
panic ->shutdown is most definitely called.  Now I am talking about the
device layer/pci layer shutdown method I don't know how gpu drivers are
wired up.  GPU land was a little strange last I looked.  Hopefully it
isn't so strange that there is a method named shutdown that is not wired
up.

Eric