Re: [PATCH] drivers/misc/cxl: Avoid unnecessary error message

[Gavin Shan <gwshan@linux.vnet.ibm.com>]

On Tue, Feb 07, 2017 at 10:12:48PM +1100, Michael Ellerman wrote:
>Andrew Donnellan <andrew.donnellan@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? :-)

Thanks,
Gavin