Re: [PATCH 2/3] PCI/AER: Disable AER service on suspend when IRQ is shared with PME

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, Jul 27, 2022 at 09:32:51AM +0800, Kai-Heng Feng wrote:
> PCIe service that shares IRQ with PME may cause spurious wakeup on
> system suspend.
> 
> PCIe Base Spec 5.0, section 5.2 "Link State Power Management" states
> that TLP and DLLP transmission is disabled for a Link in L2/L3 Ready
> (D3hot), L2 (D3cold with aux power) and L3 (D3cold), so we don't lose
> much here to disable AER during system suspend.
> 
> This is very similar to previous attempts to suspend AER and DPC [1],
> but with a different reason.
> 
> [1] https://lore.kernel.org/linux-pci/20220408153159.106741-1-kai.heng.feng@canonical.com/
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=216295
> 
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
> ---
>  drivers/pci/pcie/aer.c | 23 ++++++++++++++++++++++-
>  1 file changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index 7952e5efd6cf3..60cc373754af2 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -1372,6 +1372,26 @@ static int aer_probe(struct pcie_device *dev)
>  	return 0;
>  }
>  
> +static int aer_suspend(struct pcie_device *dev)
> +{
> +	struct aer_rpc *rpc = get_service_data(dev);
> +
> +	if (dev->shared_pme_irq)
> +		aer_disable_rootport(rpc);

aer_disable_rootport() seems like it might be overkill.  IIUC, what
we want to do here is disable AER interrupts, which should only
require clearing ROOT_PORT_INTR_ON_MESG_MASK in PCI_ERR_ROOT_COMMAND.

In addition to clearing ROOT_PORT_INTR_ON_MESG_MASK,
aer_disable_rootport() traverses the whole hierarchy, clearing
PCI_EXP_AER_FLAGS (CERE | NFERE | FERE | URRE) in PCI_EXP_DEVCTL.
I don't think these DEVCTL bits control interrupt generation, so I
don't know why we need to touch them.

aer_disable_rootport() also clears PCI_ERR_ROOT_STATUS, which I think
we should not do during suspend either.  We might want to clear it
on resume (which we already do in pci_restore_state()), but I think
generally we should preserve error information as long as it doesn't
cause trouble.

Your thoughts please :)

> +
> +	return 0;
> +}
> +
> +static int aer_resume(struct pcie_device *dev)
> +{
> +	struct aer_rpc *rpc = get_service_data(dev);
> +
> +	if (dev->shared_pme_irq)
> +		aer_enable_rootport(rpc);
> +
> +	return 0;
> +}
> +
>  /**
>   * aer_root_reset - reset Root Port hierarchy, RCEC, or RCiEP
>   * @dev: pointer to Root Port, RCEC, or RCiEP
> @@ -1441,8 +1461,9 @@ static struct pcie_port_service_driver aerdriver = {
>  	.name		= "aer",
>  	.port_type	= PCIE_ANY_PORT,
>  	.service	= PCIE_PORT_SERVICE_AER,
> -
>  	.probe		= aer_probe,
> +	.suspend	= aer_suspend,
> +	.resume		= aer_resume,
>  	.remove		= aer_remove,
>  };
>  
> -- 
> 2.36.1
>