linux-kernel - Re: [PATCH][RFT] PCI: Use pci_update_current_state() in pci_enable_device

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Message-ID: <5327028b-6e0b-e83c-b147-da083a23634c@gmail.com>
Date:   Thu, 8 Jul 2021 22:33:58 +0200
From:   Maximilian Luz <luzmaximilian@...il.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PCI <linux-pci@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: Re: [PATCH][RFT] PCI: Use pci_update_current_state() in
 pci_enable_device_flags()

On 7/8/21 3:25 PM, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Updating the current_state field of struct pci_dev the way it is done
> in pci_enable_device_flags() before calling do_pci_enable_device() may
> not work.  For example, if the given PCI device depends on an ACPI
> power resource whose _STA method initially returns 0 ("off"), but the
> config space of the PCI device is accessible and the power state
> retrieved from the PCI_PM_CTRL register is D0, the current_state
> field in the struct pci_dev representing that device will get out of
> sync with the power.state of its ACPI companion object and that will
> lead to power management issues going forward.
> 
> To avoid such issues, make pci_enable_device_flags() call
> pci_update_current_state() which takes ACPI device power management
> into account, if present, to retrieve the current power state of the
> device.
> 
> Link: https://lore.kernel.org/lkml/20210314000439.3138941-1-luzmaximilian@gmail.com/
> Reported-by: Maximilian Luz <luzmaximilian@...il.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> Hi Maximilian,
> 
> Because commit 4514d991d992 ("PCI: PM: Do not read power state in
> pci_enable_device_flags()"), the issue addressed by it is back, so
> we need an alternative way to address it.
> 
> Can you please check if this patch makes that issue go away?

Hi,

just tested this on v5.13 and it works, thanks! Feel free to add

Tested-by: Maximilian Luz <luzmaximilian@...il.com>

Regards,
Max