linux-kernel - Re: [PATCH v4 2/3] PCI/AER: Disable AER interrupt on suspend

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Date:   Mon, 24 Apr 2023 16:47:10 -0700
From:   Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>, bhelgaas@...gle.com
Cc:     mika.westerberg@...ux.intel.com, koba.ko@...onical.com,
        Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
        Oliver O'Halloran <oohall@...il.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/3] PCI/AER: Disable AER interrupt on suspend



On 4/23/23 10:52 PM, 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/
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216295
> 
> Reviewed-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> ---

IIUC, you encounter AER errors during the suspend/resume process, which
results in AER IRQ. Because AER and PME share an IRQ, it is regarded as a
spurious wake-up IRQ. So to fix it, you want to disable AER reporting,
right?

It looks like it is harmless to disable the AER during the suspend/resume
path. But, I am wondering why we get these errors? Did you check what errors
you get during the suspend/resume path? Are these errors valid?


>  drivers/pci/pcie/aer.c | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index 1420e1f27105..9c07fdbeb52d 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -1356,6 +1356,26 @@ 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);
> +	struct pci_dev *pdev = rpc->rpd;
> +
> +	aer_disable_irq(pdev);
> +
> +	return 0;
> +}
> +
> +static int aer_resume(struct pcie_device *dev)
> +{
> +	struct aer_rpc *rpc = get_service_data(dev);
> +	struct pci_dev *pdev = rpc->rpd;
> +
> +	aer_enable_irq(pdev);
> +
> +	return 0;
> +}
> +
>  /**
>   * aer_root_reset - reset Root Port hierarchy, RCEC, or RCiEP
>   * @dev: pointer to Root Port, RCEC, or RCiEP
> @@ -1420,6 +1440,8 @@ static struct pcie_port_service_driver aerdriver = {
>  	.service	= PCIE_PORT_SERVICE_AER,
>  
>  	.probe		= aer_probe,
> +	.suspend	= aer_suspend,
> +	.resume		= aer_resume,
>  	.remove		= aer_remove,
>  };
>  

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer