On Wed, Feb 08, 2017 at 01:41:19PM +1100, Michael Ellerman wrote:
>Gavin Shan <gws...@linux.vnet.ibm.com> writes:
>
>> On Wed, Feb 08, 2017 at 10:39:55AM +1100, Andrew Donnellan wrote:
>>>On 08/02/17 10:21, Gavin Shan wrote:
>>>>On Tue, Feb 07, 2017 at 10:12:48PM +1100, Michael Ellerman wrote:
>>>>>Andrew Donnellan <andrew.donnel...@au1.ibm.com> writes:
>>>>
>>>>.../...
>>>>
>>>>>>The effect of this patch is to copy the memory resources from the *real*
>>>>>>PHB to the vPHB, as given through the device tree. It shouldn't have any
>>>>>>practical effect other than squashing this message.
>>>>>
>>>>>It sounds a bit backward to me. If we don't need the resources then
>>>>>why have them?
>>>>>
>>>>>If we have code that thinks that's an error, than maybe that's what
>>>>>needs fixing, or special casing for the vPHB?
>>>>>
>>>>
>>>>Yeah, vPHB is a special case. There are basically two stages in PCI
>>>>enumeration:
>>>>probing and then resource assignment. vPHB is different from *real* PHB as
>>>>the
>>>>resource assignment is skipped on it. So vPHB doesn't need any resources to
>>>>be
>>>>populated. However, there is a check in probing stage and it's where the
>>>>warning
>>>>message comes from.
>>>>
>>>> drivers/misc/cxl/vphb.c::cxl_pci_vphb_add()
>>>> arch/powerpc/kernel/pci-common.c::pcibios_scan_phb()
>>>> pcibios_setup_phb_resources()
>>>>
>>>> static void pcibios_setup_phb_resources(struct pci_controller *hose,
>>>> struct list_head *resources)
>>>> {
>>>> :
>>>> for (i = 0; i < 3; ++i) {
>>>> res = &hose->mem_resources[i];
>>>> if (!res->flags) {
>>>> if (i == 0)
>>>> printk(KERN_ERR "PCI: Memory resource 0 not set for "
>>>> "host bridge %s (domain %d)\n",
>>>> hose->dn->full_name, hose->global_number);
>>>> continue;
>>>> }
>>>> :
>>>> }
>>>>
>>>>Alternatively, we can replace prink(KERN_ERR) with pr_debug(). It's going to
>>>>affect all PHBs including the real ones. Andrew and Michael, what do you
>>>>think? :-)
>>>
>>>In what other circumstances do we get this error printed on real PHBs?
>>>
>>
>> When hose->mem_resources[0] isn't built from PHB's device-tree node. It means
>> the device-tree node's "ranges" isn't populated correctly by loader and it
>> should be very rare ... I never saw it before.
>
>Sounds to me like we could probably just drop the warning. Or make it
>pr_devel().
>
Agree, I will drop it and post the patch shortly. Thanks for confirm.
Thanks,
Gavin
