linux-kernel - Re: [PATCH v2] PCI: rcar-host: Add static assertion to check !PCI_LOCKLESS

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Message-ID: <29ee0c03-d1d9-44f9-bdde-5c336459b097@mailbox.org>
Date: Thu, 25 Sep 2025 15:51:32 +0200
From: Marek Vasut <marek.vasut@...lbox.org>
To: Manivannan Sadhasivam <mani@...nel.org>
Cc: linux-pci@...r.kernel.org, Krzysztof Wilczyński
 <kwilczynski@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
 Geert Uytterhoeven <geert+renesas@...der.be>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Magnus Damm <magnus.damm@...il.com>,
 Marek Vasut <marek.vasut+renesas@...il.com>, Rob Herring <robh@...nel.org>,
 Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
 linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v2] PCI: rcar-host: Add static assertion to check
 !PCI_LOCKLESS_CONFIG

On 9/24/25 6:00 AM, Manivannan Sadhasivam wrote:
> On Wed, Sep 24, 2025 at 05:34:55AM +0200, Marek Vasut wrote:
>> Hello Manivannan,
>>
>> On 9/24/25 5:25 AM, Manivannan Sadhasivam wrote:
>>> On Wed, Sep 24, 2025 at 01:46:18AM +0200, Marek Vasut wrote:
>>>> This driver can not function correctly without PCIe subsystem level
>>>> config space access serialization. In case PCI_LOCKLESS_CONFIG is
>>>> ever enabled on ARM, complain loudly so the driver can be updated
>>>> accordingly.
>>>>
>>>
>>> This limitation applies to almost all host controller drivers except those used
>>> on Intel platforms like VMD and Hyper-V. So this would require adding the
>>> Kconfig dependency for all those, not just for RCAR.
>>
>> Correct.
>>
>>> We could also add the dependency to the arch Kconfig, but there is still a
>>> possibility that if the driver is used on a platform selecting
>>> PCI_LOCKLESS_CONFIG, it would be broken silently. So adding the dependency to
>>> the individual drivers that suffer from the limitation seems to be the right
>>> thing to do.
>>
>> Would you like me to send a few more patches which add !PCI_LOCKLESS_CONFIG
>> into per-driver Kconfig entries, at least for drivers where I am sure they
>> suffer from this currently hypothetical issue ...
>>
> 
> Sure.
> 
>>> Also, I'm not in favor of adding static_assert with Kconfig dependency in place.
>> ... and drop the static assert ?
>>
>> Then the drivers would at least be marked accordingly.
> 
> Yes. Better than what we have currently.
This is now done in

[PATCH] PCI: controller: Mark controllers which cannot do lockless 
config access with !PCI_LOCKLESS_CONFIG

I hope I got all of them.