linux-kernel - Re: [PATCH V8 5/6] ACPI: Support the probing on the devices which apply indirect-IO

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Date:   Sat, 1 Apr 2017 11:52:04 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     "zhichang.yuan" <zhichang.yuan02@...il.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        "zhichang.yuan" <yuanzhichang@...ilicon.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Mark Rutland <mark.rutland@....com>,
        Brian Starkey <brian.starkey@....com>,
        Olof Johansson <olof@...om.net>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        linuxarm@...wei.com,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Corey Minyard <minyard@....org>,
        Zou Rongrong <zourongrong@...il.com>,
        John Garry <john.garry@...wei.com>,
        Gabriele Paoloni <gabriele.paoloni@...wei.com>,
        kantyzc@....com, xuwei5@...ilicon.com
Subject: Re: [PATCH V8 5/6] ACPI: Support the probing on the devices which
 apply indirect-IO

On Sat, Apr 1, 2017 at 4:16 AM, zhichang.yuan <zhichang.yuan02@...il.com> wrote:
>
>
> On 04/01/2017 07:02 AM, Rafael J. Wysocki wrote:
>> On Fri, Mar 31, 2017 at 8:52 AM, zhichang.yuan
>> <yuanzhichang@...ilicon.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?
>
> Yes. The current host added in this patch with _HID "HISI0191" is on ARM64.

But the underlying mechanism is ARM-specific as well AFAICS.

> But, I think the handler driver is architecture dependent.

I guess you mean "independent"?  That doesn't matter.

If ARM64 is the only architecture to use it in foreseeable future
(which is the case for all I can say), it should go into acpi/arm64/
and please ask the maintainers thereof to review it.

Thanks,
Rafael