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

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Date:   Fri, 31 Mar 2017 14:52:46 +0800
From:   "zhichang.yuan" <yuanzhichang@...ilicon.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
CC:     <catalin.marinas@....com>, <will.deacon@....com>,
        <robh+dt@...nel.org>, <frowand.list@...il.com>,
        <bhelgaas@...gle.com>, <rafael@...nel.org>, <arnd@...db.de>,
        <linux-arm-kernel@...ts.infradead.org>, <mark.rutland@....com>,
        <brian.starkey@....com>, <olof@...om.net>,
        <lorenzo.pieralisi@....com>, <benh@...nel.crashing.org>,
        <linux-kernel@...r.kernel.org>, <linux-acpi@...r.kernel.org>,
        <linuxarm@...wei.com>, <devicetree@...r.kernel.org>,
        <linux-pci@...r.kernel.org>, <minyard@....org>,
        <zourongrong@...il.com>, <john.garry@...wei.com>,
        <gabriele.paoloni@...wei.com>, <zhichang.yuan02@...il.com>,
        <kantyzc@....com>, <xuwei5@...ilicon.com>
Subject: Re: [PATCH V8 5/6] ACPI: Support the probing on the devices which
 apply indirect-IO

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

Thanks,
Zhichang

> 
> Thanks,
> Rafael
> 
> 
> .
>