On Wed, Feb 03, 2021 at 08:53:15PM +0800, Yicong Yang wrote: > Per Downstream Port Containment Related Enhancements ECN[1], > Table 4-6 Interpretation of _OSC Control Field Returned Value, > for bit 7 of _OSC control return value: > > "If firmware allows the OS control of this feature, then, > in the context of the _OSC method the OS must ensure that > Downstream Port Containment ERR_COR signaling is disabled > as described in the PCI Express Base Specification." I think "the OS must ensure" is a typo in the spec. In the new r3.3 of the spec, it has been corrected to: If firmware allows the operating system control of this feature, then, in the context of the _OSC method firmware must clear the DPC ERR_COR Enable bit in the DPC Control Register (refer to the PCI Express Base Specification) to 0. > and PCI Express Base Specification Revision 4.0 Version 1.0 > section 6.2.10.2, Use of DPC ERR_COR Signaling: > > "...DPC ERR_COR signaling is primarily intended for use by > platform firmware..." > > Currently we don't set DPC ERR_COR enable bit, but explicitly > clear the bit to ensure it's disabled. Does this fix a problem you observed? If you're seeing a problem, and this patch fixes it, we need to do something. But if it's just to line up with the language in the spec, I think we can rely on the corrected spec language, which says the *firmware* is responsible for doing this, and leave dpc_probe() alone. > [1] Downstream Port Containment Related Enhancements ECN, > Jan 28, 2019, affecting PCI Firmware Specification, Rev. 3.2 > https://members.pcisig.com/wg/PCI-SIG/document/12888 > > Signed-off-by: Yicong Yang <yangyicong@xxxxxxxxxxxxx> > --- > drivers/pci/pcie/dpc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c > index e05aba8..5cc8ef3 100644 > --- a/drivers/pci/pcie/dpc.c > +++ b/drivers/pci/pcie/dpc.c > @@ -302,7 +302,7 @@ static int dpc_probe(struct pcie_device *dev) > pci_read_config_word(pdev, pdev->dpc_cap + PCI_EXP_DPC_CAP, &cap); > pci_read_config_word(pdev, pdev->dpc_cap + PCI_EXP_DPC_CTL, &ctl); > > - ctl = (ctl & 0xfff4) | PCI_EXP_DPC_CTL_EN_FATAL | PCI_EXP_DPC_CTL_INT_EN; > + ctl = (ctl & 0xffe4) | PCI_EXP_DPC_CTL_EN_FATAL | PCI_EXP_DPC_CTL_INT_EN; If we need to clear things here, I'd prefer to have names instead of the 0xfff4 or 0xffe4 magic numbers. > pci_write_config_word(pdev, pdev->dpc_cap + PCI_EXP_DPC_CTL, ctl); > pci_info(pdev, "enabled with IRQ %d\n", dev->irq); > > -- > 2.8.1 >
