Re: [PATCH v7] PCI/PM: Skip resuming to D0 if device is disconnected

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, Sep 08, 2025 at 10:19:15PM -0500, Mario Limonciello (AMD) wrote:
> From: Mario Limonciello <mario.limonciello@amd.com>
> 
> When a PCIe device is surprise-removed (e.g., due to a dock unplug),
> the PCI core unconfigures all downstream devices and sets their error
> state to `pci_channel_io_perm_failure`. This marks them as disconnected
> via `pci_dev_is_disconnected()`.
> 
> During device removal, the runtime PM framework may attempt to resume
> the device to D0 via `pm_runtime_get_sync()`, which calls into
> `pci_power_up()`. Since the device is already disconnected, this
> resume attempt is unnecessary and results in a predictable error.
> Avoid powering up disconnected devices by checking their status early
> in `pci_power_up()` and returning -EIO.

Hi Mario,

I forgot to ask if there are any characteristic dmesg logs and user
activities that we could include here to help users recognize this
problem.  I suppose it results in messages like this?

  pci 0000:01:00.0: Unable to change power state from D3cold to D0, device inaccessible

Maybe especially when undocking?  Although oddly a google search for
that message and "undock" finds nothing.

> Suggested-by: Lukas Wunner <lukas@wunner.de>
> Reviewed-by: Lukas Wunner <lukas@wunner.de>
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> Acked-by: Rafael J. Wysocki <rafael@kernel.org>
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
> v7:
>  * Reword commit message
>  * Rebase on v6.17-rc5
> ---
>  drivers/pci/pci.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index b0f4d98036cdd..036511f5b2625 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -1374,6 +1374,11 @@ int pci_power_up(struct pci_dev *dev)
>  		return -EIO;
>  	}
>  
> +	if (pci_dev_is_disconnected(dev)) {
> +		dev->current_state = PCI_D3cold;
> +		return -EIO;
> +	}
> +
>  	pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
>  	if (PCI_POSSIBLE_ERROR(pmcsr)) {
>  		pci_err(dev, "Unable to change power state from %s to D0, device inaccessible\n",
> -- 
> 2.43.0
>