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From: Mika Westerberg <>
To: "Rafael J. Wysocki" <>
Cc: Bjorn Helgaas <>,
	Maximilian Luz <>,
	LKML <>,
	Linux PCI <>,
	Linux PM <>,
	Linux ACPI <>
Subject: Re: [PATCH] PCI: PM: Do not read power state in pci_enable_device_flags()
Date: Wed, 17 Mar 2021 12:02:59 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <3219454.74lMxhSOWB@kreacher>

On Tue, Mar 16, 2021 at 04:51:40PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <>
> It should not be necessary to update the current_state field of
> struct pci_dev in pci_enable_device_flags() before calling
> do_pci_enable_device() for the device, because none of the
> code between that point and the pci_set_power_state() call in
> do_pci_enable_device() invoked later depends on it.
> Moreover, doing that is actively harmful in some cases.  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 it is better to leave the current_state value
> as is until it is changed to PCI_D0 by do_pci_enable_device() as
> appropriate.  However, the power state of the device is not changed
> to PCI_D0 if it is already enabled when pci_enable_device_flags()
> gets called for it, so update its current_state in that case, but
> use pci_update_current_state() covering platform PM too for that.
> Link:
> Reported-by: Maximilian Luz <>
> Tested-by: Maximilian Luz <>
> Signed-off-by: Rafael J. Wysocki <>

Reviewed-by: Mika Westerberg <>

  parent reply	other threads:[~2021-03-17 10:03 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-16 15:51 Rafael J. Wysocki
2021-03-16 22:28 ` Maximilian Luz
2021-03-17 10:02 ` Mika Westerberg [this message]
2021-03-22 14:32 ` Rafael J. Wysocki
2021-03-24 15:43   ` Rafael J. Wysocki
2021-06-21 19:27 ` Salvatore Bonaccorso
2021-06-23 17:52   ` Rafael J. Wysocki

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