Device loses its IRQ number on driver unload?

[Thomas Hellstrom]

On 03/10/2015 10:05 PM, Dave Airlie wrote:
> On 10 March 2015 at 22:55, Thomas Hellstrom <thellstrom at vmware.com> wrote:
>> On 03/09/2015 09:25 PM, Dave Airlie wrote:
>>> On 10 March 2015 at 02:02, Thomas Hellstrom <thellstrom at vmware.com> wrote:
>>>> On 03/09/2015 04:22 PM, Daniel Vetter wrote:
>>>>> On Mon, Mar 09, 2015 at 11:04:01AM +0100, Thomas Hellstrom wrote:
>>>>>> Hi,
>>>>>>
>>>>>> I'm not sure this started with 4.0 but when I rmmod the device driver
>>>>>> like so
>>>>>> rmmod vmwgfx
>>>>>>
>>>>>> The device loses its IRQ line as shown in lscpi:
>>>>>>    Flags: bus master, medium devsel, latency 64 <irq missing here>
>>>>>>
>>>>>> and a subsequent modprobe will fail since pdev->irq is 0.
>>>>>>
>>>>>> Is anyone else seeing this with other drivers?
>>>>> I seen occasionally (over the past couple of kernels) random zeros in pdev
>>>>> but dismissed it as broken machines or bugs in i915 (we have them ...).
>>>>> Usually the box died chasing a NULL pointer from pdev. Otherwise no.
>>>>> -Daniel
>>>> OK. Thanks for the info. Since in my case this is 100% reproducible I
>>>> guess I have an excellent opportunity to bisect the problem :-/
>>>>
>>> does lspci -H1, or some option like to direct access hw show it?
>>>
>>> just whether this is the kernel copy or the hw register getting messed up.
>>>
>>> Dave.
>> Hi, Dave,
>>
>> lspci -H1 indeed shows the IRQ number. It turns out that the commit
>> introduced in 4.0 breaking this is
>>
>> b4b55cda587442477a3a9f0669e26bba4b7800c0 is the first bad commit
>> commit b4b55cda587442477a3a9f0669e26bba4b7800c0
>> Author: Jiang Liu <jiang.liu at linux.intel.com>
>> Date:   Thu Feb 5 13:44:47 2015 +0800
>>
>>     x86/PCI: Refine the way to release PCI IRQ resources
>>
>>
>> It's obvious from the commit message that unloading the driver *should*
>> drop the irq resource but its not
>> obvious what's reallocating that resource on driver load...
>>
>> Anyway, it turns out that adding a
>> pci_disable_device(pdev) in the pci driver's remove() method
>> (vmw_remove() in my case) appears to fix the problem:
>> The device irq is removed on driver unload and enabled again on driver
>> load There appears to be no pci_disable_device() on driver exit in core drm.
> Yes that is because at one time pre kms if you pci disabled the VGA device,
> bad things would happen.
>
> I think with modesetting driver it shouldn't be a problem anymore.
>
> Dave.

So what's the preferred remedy here? should I file a bug against the
above commit or should we go ahead modifying
the DRM drivers?

Thanks,
Thomas



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