linux-kernel - Re: [PATCH 01/17] PCI: Add concurrency safe clear_and

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Message-ID: <ZF1qeGhCaO5+TlKu@bhelgaas>
Date:   Thu, 11 May 2023 17:21:44 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     Lukas Wunner <lukas@...ner.de>, linux-pci@...r.kernel.org,
        Rob Herring <robh@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Krzysztof Wilczy?ski <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: [PATCH 01/17] PCI: Add concurrency safe clear_and_set variants
 for LNKCTL{,2}

[+cc Emmanuel, Rafael, Heiner]

On Thu, May 11, 2023 at 11:28:05PM +0300, Ilpo Järvinen wrote:
> ...
> One question before I trying to come up something is when PCIEASPM is =n, 
> should I provide some simple function that just does the LNKCTL write to 
> disable it?

The current pci_disable_link_state() stub when CONFIG_PCIEASPM is
unset seems clearly wrong.  In fact, it returns *success* when it
actually did nothing.

I think it should probably clear ASPM Control, at least when the OS
has ownership via _OSC.  I kind of think it should do that independent
of _OSC, but that depends on the conversation at [1].

Bjorn

[1] https://lore.kernel.org/r/ZF1dsvJYYnl8Wv0v@bhelgaas