On Fri, Oct 11, 2013 at 02:33:58PM +0800, Yijing Wang wrote: >On 2013/10/11 14:16, Gavin Shan wrote: >> On Fri, Oct 11, 2013 at 04:49:56PM +1100, Benjamin Herrenschmidt wrote: >>> On Fri, 2013-09-06 at 14:30 -0600, Bjorn Helgaas wrote: >>>> On Thu, Sep 05, 2013 at 03:55:27PM +0800, Yijing Wang wrote:
.../... >>>>> Use pci_is_pcie() to simplify code. >>>>> diff --git a/arch/powerpc/kernel/eeh.c b/arch/powerpc/kernel/eeh.c >>>>> index 55593ee..6ebbe54 100644 >>>>> --- a/arch/powerpc/kernel/eeh.c >>>>> +++ b/arch/powerpc/kernel/eeh.c >>>>> @@ -189,8 +189,7 @@ static size_t eeh_gather_pci_data(struct eeh_dev >>>>> *edev, char * buf, size_t len) >>>>> } >>>>> >>>>> /* If PCI-E capable, dump PCI-E cap 10, and the AER */ >>>>> - cap = pci_find_capability(dev, PCI_CAP_ID_EXP); >>>>> - if (cap) { >>>>> + if (pci_is_pcie(dev)) { >>>>> n += scnprintf(buf+n, len-n, "pci-e cap10:\n"); >>>>> printk(KERN_WARNING >>>>> "EEH: PCI-E capabilities and status follow:\n"); >>> >>> So we remove reading of "cap", but slightly further down the code does: >>> >>> for (i=0; i<=8; i++) { >>> eeh_ops->read_config(dn, cap+4*i, 4, &cfg); >>> n += scnprintf(buf+n, len-n, "%02x:%x\n", 4*i, cfg); >>> printk(KERN_WARNING "EEH: PCI-E %02x: %08x\n", i, cfg); >>> } >>> >>> Which actually *uses* the value of "cap" ... oops :-) >>> >> >> It's my fault and I should have looked into the changes more closely. >> How about changing it like this: >> >> cap = pci_is_pcie(dev) ? pci_pcie_cap(dev) : >> pci_find_capability(dev, PCI_CAP_ID_EXP); >> if (cap) { >> ... >> } >> >> It would save some PCI-CFG access cycles for most cases :-) > >Hi Gavin, it's not your fault, it's my fault. :) > >Because pci_pcie_cap(dev) == dev->pcie_cap == pci_find_capability(dev, >PCI_CAP_ID_EXP); > >so I think it's ok to use dev->pcie_cap instead of stale "cap". > Yijing, There has one exception: dev->pcie_cap isn't updated yet. This function has possibility to be invoked before that. However, we don't have the binding (eeh device <-> PCI device) for the case. So the piece of code shouldn't be running However, it's a bit safer to have pci_find_capability(dev, PCI_CAP_ID_EXP) as well even though we needn't it for 99.9% cases if you agree :-) Thanks, Gavin _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev