linux-kernel - RE: [PATCH v2] PCI/AER: Enable SERR# forwarding in non ACPI flow

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Date:   Fri, 24 Aug 2018 12:13:24 +0000
From:   Bharat Kumar Gogada <bharatku@...inx.com>
To:     "poza@...eaurora.org" <poza@...eaurora.org>
CC:     "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        Ravikiran Gummaluri <rgummal@...inx.com>,
        "linux-pci-owner@...r.kernel.org" <linux-pci-owner@...r.kernel.org>
Subject: RE: [PATCH v2] PCI/AER: Enable SERR# forwarding in non ACPI flow

> Subject: Re: [PATCH v2] PCI/AER: Enable SERR# forwarding in non ACPI flow
> 
> On 2018-08-09 20:27, Bharat Kumar Gogada wrote:
> > As per Figure 6-3 in PCIe r4.0, sec 6.2.6, ERR_ messages will be
> > forwarded from the secondary interface to the primary interface, if
> > the SERR# Enable bit in the Bridge Control register is set.
> > Currently PCI_BRIDGE_CTL_SERR is being enabled only in ACPI flow.
> > This patch enables PCI_BRIDGE_CTL_SERR for Type-1 PCI device.
> >
> > Signed-off-by: Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>
> > ---
> >  drivers/pci/pcie/aer.c |   23 +++++++++++++++++++++++
> >  1 files changed, 23 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c index
> > a2e8838..4fb0d24 100644
> > --- a/drivers/pci/pcie/aer.c
> > +++ b/drivers/pci/pcie/aer.c
> > @@ -343,6 +343,20 @@ int pci_enable_pcie_error_reporting(struct
> > pci_dev
> > *dev)
> >  	if (!dev->aer_cap)
> >  		return -EIO;
> >
> > +	if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
> > +		u16 control;
> > +
> > +		/*
> > +		 * A Type-1 PCI bridge will not forward ERR_ messages
> coming
> > +		 * from an endpoint if SERR# forwarding is not enabled.
> > +		 */
> > +		pci_read_config_word(dev, PCI_BRIDGE_CONTROL,
> &control);
> > +		if (!(control & PCI_BRIDGE_CTL_SERR)) {
> > +			control |= PCI_BRIDGE_CTL_SERR;
> > +			pci_write_config_word(dev, PCI_BRIDGE_CONTROL,
> control);
> > +		}
> > +	}
> > +
> >  	return pcie_capability_set_word(dev, PCI_EXP_DEVCTL,
> > PCI_EXP_AER_FLAGS);  }
> > EXPORT_SYMBOL_GPL(pci_enable_pcie_error_reporting);
> > @@ -352,6 +366,15 @@ int pci_disable_pcie_error_reporting(struct
> > pci_dev *dev)
> >  	if (pcie_aer_get_firmware_first(dev))
> >  		return -EIO;
> >
> > +	if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
> > +		u16 control;
> > +
> > +		/* Clear SERR Forwarding */
> > +		pci_read_config_word(dev, PCI_BRIDGE_CONTROL,
> &control);
> > +		control &= ~PCI_BRIDGE_CTL_SERR;
> > +		pci_write_config_word(dev, PCI_BRIDGE_CONTROL, control);
> > +	}
> > +
> >  	return pcie_capability_clear_word(dev, PCI_EXP_DEVCTL,
> >  					  PCI_EXP_AER_FLAGS);
> >  }
> 
> 
> Hi Bjorn,
> 
> I made some comments on patchv1., same I am putting it across here.
> 
> what about hot-plug case ?
> should not aer_init() call pci_enable_pcie_error_reporting() for all the
> downstream pci_dev ?
> and remove all the calls from drivers..
> aer_init will be called for each device (pci_dev) while pciehp does re-
> enumeration.
> so probable we might want to call pci_enable_pcie_error_reporting() but
> that dictates the design where AER framework is taking decision to enable
> error reporting on behalf of drivers as well.
> but thats fine I think, if drivers do not want to participate then they have to
> call  pci_disable_pcie_error_reporting explicitly.
> does this make sense ?
> 
Hi Bjorn,
Can you please comment on this.

Bharat