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SubjectRe: [PATCH] PCI/AER: Enable SERR# forwarding in non ACPI flow
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@xilinx.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..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

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