Re: [PATCH 1/2] PCI/AER: Do not reset the device status if doing firmware first handling.

[Bjorn Helgaas <helgaas@kernel.org>]

[+cc Sathy]

On Fri, May 22, 2020 at 01:31:33AM +0800, Jonathan Cameron wrote:
> pci_aer_clear_device_status() currently resets the device status even when
> firmware first handling is going on.  In particular it resets it on the
> root port.
>
> This has been discussed previously
> https://lore.kernel.org/patchwork/patch/427375/.

I don't think this reference is really pertinent, is it?  That patch
to b2c8881da764 changes pci_cleanup_aer_uncorrect_error_status() so it
doesn't clear PCI_ERR_UNCOR_STATUS in "firmware-first" mode.

But your patch only affects PCI_EXP_DEVSTA, not PCI_ERR_UNCOR_STATUS.

> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> ---
>  drivers/pci/pcie/aer.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index f4274d301235..43e78b97ace6 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -373,6 +373,9 @@ void pci_aer_clear_device_status(struct pci_dev *dev)
>  {
>  	u16 sta;
>  
> +	if (pcie_aer_get_firmware_first(dev))
> +		return;

This needs to be adjusted because pcie_aer_get_firmware_first() no
longer exists after 708b20003624 ("PCI/AER: Remove HEST/FIRMWARE_FIRST
parsing for AER ownership").

This will use the _OSC AER ownership bit to gate clearing of the
status bits in the PCIe capability (not the AER capability).

I think that's the right thing to do, but it's certainly not obvious
from the _OSC description in the PCI Firmware Spec r3.2.  I think we
need a pointer to the ECN that clarifies this, i.e., sec 4.5.1 of:

  System Firmware Intermediary (SFI) _OSC and DPC Updates ECN, Feb 24,
  2020, affecting PCI Firmware Specification, Rev. 3.2
  https://members.pcisig.com/wg/PCI-SIG/document/14076

>  	pcie_capability_read_word(dev, PCI_EXP_DEVSTA, &sta);
>  	pcie_capability_write_word(dev, PCI_EXP_DEVSTA, sta);
>  }
> -- 
> 2.19.1
>