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

[poza]

On 2018-07-18 19:04, Bharat Kumar Gogada wrote:
> > 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.
> I'm not aware of other platforms, can you please give an example of a 
> platform
> how it decides to set this in firmware ?
>
> > although,
> > There are 2 cases
> > Hotplug capable bridge and otherwise.
>
> Yes, what about an RP which supports only AER but doesn't support 
> Hotplug ?
> If we have this patch we can set this bit without firmware also.
> > 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 ?
> Hi all, do you have any inputs on this ?

I have thought more on this..but needs separate discussion hence will be 
forking the separate thread.
If I choose to make some more patches based on this patch, this patch 
can remain as is and will be included with your authorship.

Regards,
Oza.

> Regards,
> Bharat