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

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.











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