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SubjectRe: [PATCH] PCI/AER: Enable SERR# forwarding in non ACPI flow
On 2018-08-02 11:53, poza@codeaurora.org wrote:
> On 2018-08-01 04:17, Bjorn Helgaas wrote:
>> On Thu, Jul 12, 2018 at 08:15:19PM +0530, 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.
>>
>> This does seem broken.
>>
>> Figure 6-3 in PCIe r4.0, sec 6.2.6, would be a helpful reference to
>> include in the commit log.
>>
>> Semi-related question: there are about 40 drivers that call
>> pci_enable_pcie_error_reporting() and
>> pci_disable_pcie_error_reporting(). I see that the PCI core
>> calls pci_enable_pcie_error_reporting() for Root Ports and Switch
>> Ports in this path:
>>
>> aer_probe # for root ports only
>> aer_enable_rootport
>> set_downstream_devices_error_reporting
>> set_device_error_reporting
>> if (ROOT_PORT || UPSTREAM || DOWNSTREAM)
>> pci_enable_pcie_error_reporting
>> pci_walk_bus(..., set_device_error_reporting)
>>
>> But the core doesn't call pci_enable_pcie_error_reporting() for
>> endpoints. I wonder why not. Could we? And then remove the calls
>> from those drivers? If PCI_EXP_AER_FLAGS should only be set if the
>> driver is prepared, the pci_driver.err_handler would be a good hint.
>> But I suspect we could do something sensible and at least report
>> errors even if the driver doesn't have err_handler callbacks.
>>
>
> 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 ?

>> On MIPS Octeon, it looks like pcibios_plat_dev_init() does already set
>> PCI_EXP_AER_FLAGS for every device.
>>
>> But this question is obviously far beyond the scope of this current
>> patch.
>>
>>> 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) {
>>
>> I think this test needs to be refined a little bit. If the kernel
>> happens to be built with CONFIG_ACPI=y but the current platform
>> doesn't support ACPI, we still want to set PCI_BRIDGE_CTL_SERR,
>> don't we?
>>
>>> + 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);
>>> }
>>> --
>>> 1.7.1
>>>

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