linux-kernel - Re: [PATCH] of: treat PCI config space as IORESOURCE

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Message-ID: <CAErSpo7qEhJyUAu58R8g6+AEhRGo_+Vv0EMgkK+3ZQOU9+jmhg@mail.gmail.com>
Date:	Thu, 29 May 2014 19:29:31 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Kumar Gala <galak@...eaurora.org>,
	Rob Herring <robherring2@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	Grant Likely <grant.likely@...aro.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Kishon Vijay Abraham I <kishon@...com>
Subject: Re: [PATCH] of: treat PCI config space as IORESOURCE_MEM type

On Thu, May 29, 2014 at 6:56 PM, Liviu Dudau <liviu@...au.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@...il.com> wrote:
>>
>> > On Thu, May 29, 2014 at 11:03 AM, Kumar Gala <galak@...eaurora.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@...eaurora.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
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