Subject: Re: [PATCH v2 1/2] PCI/AER: Disable AER service when link is in L2/L3 ready, L2 and L3 state

From: Sathyanarayanan Kuppuswamy <[email-masked]>
Date: Sat, 19 Mar 2022 13:38:39 -0700

On 1/26/22 6:54 PM, Kai-Heng Feng wrote:
> Commit 50310600ebda ("iommu/vt-d: Enable PCI ACS for platform opt in
> hint") enables ACS, and some platforms lose its NVMe after resume from

Why enabling ACS makes platform lose NVMe? Can you add more details
about the problem?

> S3:
> [   50.947816] pcieport 0000:00:1b.0: DPC: containment event, status:0x1f01 source:0x0000
> [   50.947817] pcieport 0000:00:1b.0: DPC: unmasked uncorrectable error detected
> [   50.947829] pcieport 0000:00:1b.0: PCIe Bus Error: severity=Uncorrected (Non-Fatal), type=Transaction Layer, (Receiver ID)
> [   50.947830] pcieport 0000:00:1b.0:   device [8086:06ac] error status/mask=00200000/00010000
> [   50.947831] pcieport 0000:00:1b.0:    [21] ACSViol                (First)
> [   50.947841] pcieport 0000:00:1b.0: AER: broadcast error_detected message
> [   50.947843] nvme nvme0: frozen state error detected, reset controller
> 
> It happens right after ACS gets enabled during resume.
> 
> There's another case, when Thunderbolt reaches D3cold:
> [   30.100211] pcieport 0000:00:1d.0: AER: Uncorrected (Non-Fatal) error received: 0000:00:1d.0
> [   30.100251] pcieport 0000:00:1d.0: PCIe Bus Error: severity=Uncorrected (Non-Fatal), type=Transaction Layer, (Requester ID)
> [   30.100256] pcieport 0000:00:1d.0:   device [8086:7ab0] error status/mask=00100000/00004000
> [   30.100262] pcieport 0000:00:1d.0:    [20] UnsupReq               (First)
> [   30.100267] pcieport 0000:00:1d.0: AER:   TLP Header: 34000000 08000052 00000000 00000000
> [   30.100372] thunderbolt 0000:0a:00.0: AER: can't recover (no error_detected callback)

no callback message means one or more devices in the given port does not
support error handler. How is this related to ACS?

> [   30.100401] xhci_hcd 0000:3e:00.0: AER: can't recover (no error_detected callback)
> [   30.100427] pcieport 0000:00:1d.0: AER: device recovery failed
> 
> So disable AER service to avoid the noises from turning power rails
> on/off when the device is in low power states (D3hot and D3cold), as
> PCIe spec "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).
> 
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=209149
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=215453
> Fixes: 50310600ebda ("iommu/vt-d: Enable PCI ACS for platform opt in hint")
> Signed-off-by: Kai-Heng Feng <[email-masked]>
> ---
> v2:
>   - Wording change.
> 
>   drivers/pci/pcie/aer.c | 31 +++++++++++++++++++++++++------
>   1 file changed, 25 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index 9fa1f97e5b270..e4e9d4a3098d7 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -1367,6 +1367,22 @@ 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);
> +
> +	aer_disable_rootport(rpc);
> +	return 0;
> +}
> +
> +static int aer_resume(struct pcie_device *dev)
> +{
> +	struct aer_rpc *rpc = get_service_data(dev);
> +
> +	aer_enable_rootport(rpc);
> +	return 0;
> +}
> +
>   /**
>    * aer_root_reset - reset Root Port hierarchy, RCEC, or RCiEP
>    * @dev: pointer to Root Port, RCEC, or RCiEP
> @@ -1433,12 +1449,15 @@ static pci_ers_result_t aer_root_reset(struct pci_dev *dev)
>   }
>   
>   static struct pcie_port_service_driver aerdriver = {
> -	.name		= "aer",
> -	.port_type	= PCIE_ANY_PORT,
> -	.service	= PCIE_PORT_SERVICE_AER,
> -
> -	.probe		= aer_probe,
> -	.remove		= aer_remove,
> +	.name			= "aer",
> +	.port_type		= PCIE_ANY_PORT,
> +	.service		= PCIE_PORT_SERVICE_AER,
> +	.probe			= aer_probe,
> +	.suspend		= aer_suspend,
> +	.resume			= aer_resume,
> +	.runtime_suspend	= aer_suspend,
> +	.runtime_resume		= aer_resume,
> +	.remove			= aer_remove,
>   };
>   
>   /**

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer