Re: [PATCH v2] platform/x86: p2sb: Defer P2SB device scan when P2SB device has func 0

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 3/4/24 3:35 PM, Andy Shevchenko wrote:
> On Mon, Mar 04, 2024 at 03:24:58PM +0100, Hans de Goede wrote:
>> On 3/4/24 3:17 PM, Andy Shevchenko wrote:
>>> On Mon, Mar 04, 2024 at 04:09:49PM +0200, Andy Shevchenko wrote:
>>>> On Mon, Mar 04, 2024 at 02:59:57PM +0100, Hans de Goede wrote:
>>>>> On 3/4/24 1:13 PM, Shinichiro Kawasaki wrote:
>>>>>> On Mar 04, 2024 / 12:04, Hans de Goede wrote:
> 
> ...
> 
>>>>>> Thanks for sharing the insights.
>>>>>
>>>>> Looking closer at the actual unhiding I don't think accessing func 0
>>>>> is the problem. The unhiding is always done on function 0 even when
>>>>> retreiving the bar for function 2 (the SPI function).
>>>>>
>>>>> So taking that into account, as mentioned in the bugzilla, I think
>>>>> the problem is probing the other functions (1, 3-7) by calling
>>>>> pci_scan_single_device() on them.
>>>>
>>>> So, why we can't simply call pci_dev_present() on the function in a loop?
>>>
>>> pci_device_is_present()
>>
>> That takes a pci_dev as argument which we only have after calling
>> pci_scan_single_device() and the calling of pci_scan_single_device()
>> on some of the other functions is what is suspected of maybe causing
>> the issue.
>>
>> Also it is likely that if pci_scan_single_device() is actually
>> a problem that then what is a problem is running it on an actual
>> present device.
> 
> Which is weird. But okay, let's work around first the real issue, then
> if I have time I will look into datasheet to see if there is anything
> special about P2SB device(s).

Note atm pci_scan_single_device() on one of the "other" being
the problem is still only a theory!

It is also possible that pci_scan_single_device() on the P2SB
itself is somehow an issue on this laptop, since on this laptop
p2sb_bar() is only called for the SPI controller, so before
the caching to avoid the deadlock issue pci_scan_single_device()
was not called on the P2SB devfn itself.

Regards,

Hans