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

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Message-ID: <1908501.jAQQKvjW4f@aspire.rjw.lan>
Date:   Thu, 30 Mar 2017 22:31:10 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     "zhichang.yuan" <yuanzhichang@...ilicon.com>
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

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?

Thanks,
Rafael