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

[Andrew Donnellan]

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.donnellan at 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?

-- 
Andrew Donnellan              OzLabs, ADL Canberra
andrew.donnellan at au1.ibm.com  IBM Australia Limited