linux-kernel - Re: [PATCH v4] PCI/AER: Enable error reporting for all ports

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Message-ID: <20181019011135.GP5906@bhelgaas-glaptop.roam.corp.google.com>
Date:   Thu, 18 Oct 2018 20:11:35 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Keith Busch <keith.busch@...el.com>
Cc:     Jon Derrick <jonathan.derrick@...el.com>,
        Dongdong Liu <liudongdong3@...wei.com>,
        Sinan Kaya <okaya@...nel.org>,
        Oza Pawandeep <poza@...eaurora.org>,
        Matthew Wilcox <willy@...radead.org>,
        Lukas Wunner <lukas@...ner.de>, Christoph Hellwig <hch@....de>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] PCI/AER: Enable error reporting for all ports

On Thu, Oct 18, 2018 at 05:03:13PM -0600, Keith Busch wrote:
> On Thu, Oct 18, 2018 at 03:53:58PM -0500, Bjorn Helgaas wrote:
> > Change the AER service driver so it binds to *all* PCIe Ports,
> > including Switch Upstream and Downstream Ports.  Enable AER error
> > reporting for all these Ports, but not for any children.
> 
> I'm looking at this again and think enabling/disabling error
> reporting for ports is the responsibility of the port driver, not
> the AER service.

That's an interesting idea.  Can you expand on this a little more?
Why is it the responsibility of the port driver?

Do you think pci_enable_pcie_error_reporting() shouldn't be part of
the AER service because it updates the Device Control register, which
is in the PCIe Capability, not the AER Capability?

What about pci_aer_clear_device_status(), which clears Device Status,
which is also in the PCIe Capability?

> The following should do the same as this patch, but without making
> AER driver handle non-root ports.  The report enabling/disabling
> functions are already stubbed for '!CONFIG_PCIE_AER' and have checks
> for aer_cap and firmware first.

If we thought we should enable error reporting *always*, regardless of
whether the AER service is enabled, this would make perfect sense to
me, and I might suggest doing it in an even more generic place like
pci_configure_device() or pci_init_capabilities().

But that doesn't seem like where you're headed.  It seems like you
still only want error reporting enabled when CONFIG_PCIEAR=y.  If
that's the case, it seems like doing it in portdrv only obfuscates the
connection with AER.  When CONFIG_PCIEAER is unset, the portdrv code
*looks* like it's doing something but it's really not because of the
#ifdef magic.

> A real patch for this could even make this remove all the aer
> specific error report enabling, so it'd be a net-loss in code lines.
> :)
> 
> ---
> diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c
> index 0acca3596807..f129a33c8303 100644
> --- a/drivers/pci/pcie/portdrv_pci.c
> +++ b/drivers/pci/pcie/portdrv_pci.c
> @@ -122,12 +122,13 @@ static int pcie_portdrv_probe(struct pci_dev *dev,
>  		pm_runtime_put_autosuspend(&dev->dev);
>  		pm_runtime_allow(&dev->dev);
>  	}
> -
> +	pci_enable_pcie_error_reporting(dev);
>  	return 0;
>  }
>  
>  static void pcie_portdrv_remove(struct pci_dev *dev)
>  {
> +	pci_disable_pcie_error_reporting(dev);
>  	if (pci_bridge_d3_possible(dev)) {
>  		pm_runtime_forbid(&dev->dev);
>  		pm_runtime_get_noresume(&dev->dev);
> --