Date: Fri, 20 Nov 2015 10:18:40 +0000
From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Tomasz Nowicki <tn@semihalf.com>, Arnd Bergmann <arnd@arndb.de>,
        Bjorn Helgaas <bhelgaas@google.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Hanjun Guo <hanjun.guo@linaro.org>, Liviu Dudau <Liviu.Dudau@arm.com>,
        linux-acpi@vger.kernel.org, linux-pci@vger.kernel.org,
        linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [Patch v7 4/7] PCI/ACPI: Add interface acpi_pci_root_create()
Message-ID: <20151120101840.GD15819@red-moon>
References: <564185B6.8040006@linux.intel.com>
 <20151111174647.GA30051@red-moon>
 <56445117.8090307@linux.intel.com>
 <56449246.2010308@semihalf.com>
 <56449C55.2090001@linux.intel.com>
 <5644A613.2010304@semihalf.com>
 <5644AAB9.6010700@linux.intel.com>
 <5645DE3A.7040406@semihalf.com>
 <20151113170316.GB15253@red-moon>
 <56462294.3060701@linux.intel.com>
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Hi Jiang,

On Sat, Nov 14, 2015 at 01:49:08AM +0800, Jiang Liu wrote:

[...]

> > Not really. My concern is that there might be platforms out there with
> > an offset between the CPU and PCI physical address spaces, and if we
> > remove the offset value in acpi_decode_space we can break them,
> > because in the kernel struct resource data we have to have CPU physical
> > addresses, not PCI ones. If offset == 0, we are home and dry, I do not
> > understand why that's a given, which is what we would assume if Jiang's
> > patch is merged as-is unless I am mistaken.
> We try to exclude offset from struct resource in generic ACPI code,
> and it's the arch's responsibility to decide how to manipulate struct
> resource object if offset is not zero.
> 
> Currently offset is always zero for x86, and IA64 has arch specific
> code to handle non-zero offset. So we should be safe without breaking
> existing code. For ARM64, it's a little different from IA64 so it's
> hard to share code between IA64 and ARM64.

Can you drop the patch on the mailing lists please, we actually need it
to get ACPI ARM64 PCIe support in the kernel, please let me know how
you want to handle this and if you need any help.

Thanks,
Lorenzo
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