Re: [PATCH 1/2] PCI: rcar-host: Drop PMSR spinlock

[Marek Vasut <marek.vasut@mailbox.org>]

On 9/22/25 12:53 PM, Geert Uytterhoeven wrote:

Hello Geert,

>>> My only worry is that PCI_LOCKLESS_CONFIG may be selected on non-x86
>>> one day, breaking your assumptions.  IMHO, the mechanism behind this
>>> config option, introduced in commit 714fe383d6c9bd95 ("PCI: Provide
>>> Kconfig option for lockless config space accessors") looks very fragile
>>> to me: it is intended to be selected by an architecture, if "all" low
>>> level PCI configuration space accessors use their own serialization or
>>> can operate completely lockless.  Usually we use the safer, inverted
>>> approach (PCI_NOLOCKLESS_CONFIG), to be selected by all drivers that
>>> do not adhere to the assumption.
>>> But perhaps I am missing something, and this does not depend on
>>> individual PCIe host drivers?
>>>
>>> Regardless, improving that is clearly out-of-scope for this patch...
>>
>> I could send a follow up patch which would add build-time assertion that
>> PCI_LOCKLESS_CONFIG must not be selected for this driver to work. Would
>> that be an option ?
> 
> Or simply just "depends on !CONFIG_PCI_LOCKLESS_CONFIG"?
> What do the PCIe maintainers think?
I send a patch in the meantime:

[PATCH] PCI: rcar-host: Add static assertion to check !PCI_LOCKLESS_CONFIG