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SubjectRe: [PATCH v5 04/12] PCI: brcmstb: add dma-range mapping for inbound traffic
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On 09/19/2018 07:19 PM, Ard Biesheuvel wrote:
> On 19 September 2018 at 07:31, Jim Quinlan <jim2101024@gmail.com> wrote:
>> The Broadcom STB PCIe host controller is intimately related to the
>> memory subsystem. This close relationship adds complexity to how cpu
>> system memory is mapped to PCIe memory. Ideally, this mapping is an
>> identity mapping, or an identity mapping off by a constant. Not so in
>> this case.
>>
>> Consider the Broadcom reference board BCM97445LCC_4X8 which has 6 GB
>> of system memory. Here is how the PCIe controller maps the
>> system memory to PCIe memory:
>>
>> memc0-a@[ 0....3fffffff] <=> pci@[ 0....3fffffff]
>> memc0-b@[100000000...13fffffff] <=> pci@[ 40000000....7fffffff]
>> memc1-a@[ 40000000....7fffffff] <=> pci@[ 80000000....bfffffff]
>> memc1-b@[300000000...33fffffff] <=> pci@[ c0000000....ffffffff]
>> memc2-a@[ 80000000....bfffffff] <=> pci@[100000000...13fffffff]
>> memc2-b@[c00000000...c3fffffff] <=> pci@[140000000...17fffffff]
>>
>
> So is describing this as
>
> dma-ranges = <0x0 0x0 0x0 0x0 0x0 0x40000000>,
> <0x0 0x40000000 0x1 0x0 0x0 0x40000000>,
> <0x0 0x80000000 0x0 0x40000000 0x0 0x40000000>,
> <0x0 0xc0000000 0x3 0x0 0x0 0x40000000>,
> <0x1 0x0 0x0 0x80000000 0x0 0x40000000>,
> <0x1 0x40000000 0x0 0xc0000000 0x0 0x40000000>;
>
> not working for you? I haven't tried this myself, but since DT permits
> describing the inbound mappings this way, we should fix the code if it
> doesn't work at the moment.

You mean encoding the memory controller index in the first cell? If that
works, that's indeed a much cleaner solution, though is it standard
compliant in any form?
--
Florian

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