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

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Tue, 16 Jun 2020 12:47:31 -0500
Bjorn Helgaas <helgaas@kernel.org> wrote:

> [+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.

I'll be honest I've mostly forgotten my reasoning behind including that
reference.  Might have been as simple as I got lost in the renames.

I'll drop the reference.

> 
> > 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

Thanks. I'll add that (though can't check the document currently
for reasons you can probably figure out *sigh*)

Note this patch is rather tangential to patch 2 which is the one
I really need feedback on.  Whilst this appeared to be
wrong it is 'mostly harmless'.

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