Re: [PATCH] PCI/AER: Enable SERR# forwarding in non ACPI flow

[poza]

On 2018-07-13 19:25, Bharat Kumar Gogada wrote:
> > > Currently PCI_BRIDGE_CTL_SERR is being enabled only in ACPI flow.
> > > This bit is required for forwarding errors reported by EP devices to
> > > upstream device.
> > > This patch enables SERR# for Type-1 PCI device.
> > >
> > > Signed-off-by: Bharat Kumar Gogada <bharat.kumar.gogada@xxxxxxxxxx>
> > > ---
> > >  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..943e084 100644
> > > --- a/drivers/pci/pcie/aer.c
> > > +++ b/drivers/pci/pcie/aer.c
> > > @@ -343,6 +343,19 @@ int pci_enable_pcie_error_reporting(struct
> > > pci_dev
> > > *dev)
> > >  	if (!dev->aer_cap)
> > >  		return -EIO;
> > >
> > > +	if (!IS_ENABLED(CONFIG_ACPI) &&
> > > +	    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);
> > > +		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 +365,16 @@ int pci_disable_pcie_error_reporting(struct
> > > pci_dev *dev)
> > >  	if (pcie_aer_get_firmware_first(dev))
> > >  		return -EIO;
> > >
> > > +	if (!IS_ENABLED(CONFIG_ACPI) &&
> > > +	    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);
> > >  }
> >
> >
> > Should this configuration no be set by Firmware ? why should Linux 
> > dictate it
> > ?
> Hi Oza, Can you please let us know why this should be set by firmware ?
> Spec clearly states ERR_CORR,ERR_FATAL/NON FATAL will be forwarded
> only if this bit is set.
> If linux AER service is being enabled without checking/setting this
> bit, then AER service will
> not do anything even ERR_* is seen on link.
>
> Regards,
> Bharat


The ERR_* to be forwarded or not to be forwarded could be decision of 
the platform.
hence I think it is best left to firmware to decide if it want to enable 
this for particular platform.

although,
There are 2 cases
Hotplug capable bridge and otherwise.

1) If Firmware sets them, I do not think during enumeraion linux will 
loose those settings.

2) I do not see any integration of hotplug with AER currently, so if the 
PCIe switch is plugged into Hotplug
capable RP, I am not very sure if this functions get called.

Keith, Lukas and Bjorn any comments ?

Regards,
Oza.