linux-kernel - Re: [PATCH v2 9/9] PCI: PM: Set power.strict_midlayer in pci_pm

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Message-ID: <20250626205923.GA1639790@bhelgaas>
Date: Thu, 26 Jun 2025 15:59:23 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Linux PM <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux ACPI <linux-acpi@...r.kernel.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: Re: [PATCH v2 9/9] PCI: PM: Set power.strict_midlayer in
 pci_pm_init()

On Thu, Jun 26, 2025 at 08:15:05PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> The PCI bus type does not expect its runtime PM callbacks,
> pci_pm_runtime_suspend() and pci_pm_runtime_resume(), to be invoked at
> any point during system-wide suspend and resume, so make it express
> that expectation by setting power.strict_midlayer for all PCI devices
> in pci_pm_prepare() and clear it in pci_pm_complete().
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Previous PM-related patches in drivers/pci/ use a subject line like:

  PCI/PM: ...

Would be cool if there were hints about what
dev_pm_set_strict_midlayer() means.  Maybe the comment in
get_callback() is enough, but it takes a little work to find it.

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

> ---
> 
> v1 -> v2:
>    * Set and clear the new flag in "prepare" and "complete" to allow
>      pm_runtime_force_suspend() invoked from driver remove callbacks to
>      work.
>    * Update subject and changelog.
> 
> ---
>  drivers/pci/pci-driver.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -708,6 +708,8 @@
>  	struct pci_dev *pci_dev = to_pci_dev(dev);
>  	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
>  
> +	dev_pm_set_strict_midlayer(dev, true);
> +
>  	if (pm && pm->prepare) {
>  		int error = pm->prepare(dev);
>  		if (error < 0)
> @@ -749,6 +751,8 @@
>  		if (pci_dev->current_state < pre_sleep_state)
>  			pm_request_resume(dev);
>  	}
> +
> +	dev_pm_set_strict_midlayer(dev, false);
>  }
>  
>  #else /* !CONFIG_PM_SLEEP */
> 
> 
>