Re: [PATCH 2/3] PCI: Do not poll for PME if the device is in D3cold

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Wednesday, June 5, 2019 4:58:19 PM CEST Mika Westerberg wrote:
> PME polling does not take into account that a device that is directly
> connected to the host bridge may go into D3cold as well. This leads to a
> situation where the PME poll thread reads from a config space of a
> device that is in D3cold and gets incorrect information because the
> config space is not accessible.
> 
> Here is an example from Intel Ice Lake system where two PCIe root ports
> are in D3cold (I've instrumented the kernel to log the PMCSR register
> contents):
> 
>   [   62.971442] pcieport 0000:00:07.1: Check PME status, PMCSR=0xffff
>   [   62.971504] pcieport 0000:00:07.0: Check PME status, PMCSR=0xffff
> 
> Since 0xffff is interpreted so that PME is pending, the root ports will
> be runtime resumed. This repeats over and over again essentially
> blocking all runtime power management.
> 
> Prevent this from happening by checking whether the device is in D3cold
> before its PME status is read.
> 
> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

> ---
>  drivers/pci/pci.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 87a1f902fa8e..720da09d4d73 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -2060,6 +2060,13 @@ static void pci_pme_list_scan(struct work_struct *work)
>  			 */
>  			if (bridge && bridge->current_state != PCI_D0)
>  				continue;
> +			/*
> +			 * If the device is in D3cold it should not be
> +			 * polled either.
> +			 */
> +			if (pme_dev->dev->current_state == PCI_D3cold)
> +				continue;
> +
>  			pci_pme_wakeup(pme_dev->dev, NULL);
>  		} else {
>  			list_del(&pme_dev->list);
>