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SubjectRe: [PATCH V8 5/6] ACPI: Support the probing on the devices which apply indirect-IO
On Fri, Mar 31, 2017 at 8:52 AM, zhichang.yuan
<yuanzhichang@hisilicon.com> wrote:
> Hi, Rafael,
>
> Thanks for reviewing this!
>
> On 2017/3/31 4:31, Rafael J. Wysocki wrote:
>> On Thursday, March 30, 2017 11:26:58 PM zhichang.yuan wrote:
>>> On some platforms(such as Hip06/Hip07), the legacy ISA/LPC devices access I/O
>>> with some special host-local I/O ports known on x86. To access the I/O
>>> peripherals, an indirect-IO mechanism is introduced to mapped the host-local
>>> I/O to system logical/fake PIO similar the PCI MMIO on architectures where no
>>> separate I/O space exists. Just as PCI MMIO, the host I/O range should be
>>> registered before probing the downstream devices and set up the I/O mapping.
>>> But current ACPI bus probing doesn't support these indirect-IO hosts/devices.
>>>
>>> This patch introdueces a new ACPI handler for this device category. Through the
>>> handler attach callback, the indirect-IO hosts I/O registration is done and
>>> all peripherals' I/O resources are translated into logic/fake PIO before
>>> starting the enumeration.
>>
>> Can you explain to me briefly what exactly this code is expected to be doing?
>
> As you know currently for ARM architecture IO space is memory mapped and
> is only used by pci devices. The port number is dynamically allocated
> converting the device IO address into a PIO token: i.e.
> http://lxr.free-electrons.com/source/drivers/acpi/pci_root.c#L745
> This patch is meant to support a new class of IO host controller
> that are not PCI based and that still require to have the IO addresses
> be translated in the same PIO token space as the PCI controller

IOW, this is ARM-specific, right?

Thanks,
Rafael

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