Re: [PATCH] of: treat PCI config space as IORESOURCE_MEM type

Bjorn Helgaas
2014-05-30T01:29:57Z

On Thu, May 29, 2014 at 6:56 PM, Liviu Dudau <liviu@dudau.co.uk> wrote:
> On Thu, May 29, 2014 at 03:51:28PM -0500, Kumar Gala wrote:
>>
>> On May 29, 2014, at 3:44 PM, Rob Herring <robherring2@gmail.com> wrote:
>>
>> > On Thu, May 29, 2014 at 11:03 AM, Kumar Gala <galak@codeaurora.org> wrote:
>> >> If we have a PCI config space specified in something like a ranges
>> >> property we should treat it as memory type resource.
>> >
>> > Config space should not be in ranges[1]. We have some cases that are,
>> > but we don't want new ones.
>>
>> For the cases we have I agree, however an ECAM based cfg seems completely legit.
>>
>> >> Signed-off-by: Kumar Gala <galak@codeaurora.org>
>> >> ---
>> >> drivers/of/address.c | 3 +++
>> >> 1 file changed, 3 insertions(+)
>> >>
>> >> diff --git a/drivers/of/address.c b/drivers/of/address.c
>> >> index cb4242a..4e7ee59 100644
>> >> --- a/drivers/of/address.c
>> >> +++ b/drivers/of/address.c
>> >> @@ -122,6 +122,9 @@ static unsigned int of_bus_pci_get_flags(const __be32 *addr)
>> >> u32 w = be32_to_cpup(addr);
>> >>
>> >> switch((w >> 24) & 0x03) {
>> >> + case 0x00: /* cfg space */
>> >> + flags |= IORESOURCE_MEM;
>> >> + break;
>> >
>> > How would you then distinguish actual memory ranges?
>>
>> One assumes you are still looking at pci_space as part of of_pci_range
>
> That doesn't happen when you start scanning the bus. The existing code will
> use the IORESOURCE_MEM for allocating memory space for devices, which is
> not what you want. Did you test your patch on any PCI system? I'm pretty
> sure that with my patch series that tries to make a generic framework for
> host controllers this will fail.
>
> We really need a IORESOURCE_CFG flag for this space.

Maybe, but I'm not convinced yet. The existing IORESOURCE_TYPE_BITS
types are for things that are mutually exclusive address spaces. I
think this discussion is about ECAM, where the CPU side is definitely
in the same address space (IORESOURCE_MEM) as RAM, APICs, host bridge
apertures, device MMIO, etc. The ECAM area must appear in the
iomem_resource tree so we avoid it when allocating other areas.

>> > [1] http://www.spinics.net/lists/linux-pci/msg30585.html