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

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Date:   Sun, 2 Apr 2017 14:58:17 +0000
From:   Gabriele Paoloni <gabriele.paoloni@...wei.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        "zhichang.yuan" <zhichang.yuan02@...il.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>
CC:     Yuanzhichang <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 <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>,
        "kantyzc@....com" <kantyzc@....com>,
        "xuwei (O)" <xuwei5@...ilicon.com>
Subject: RE: [PATCH V8 5/6] ACPI: Support the probing on the devices which
 apply indirect-IO

Hi Rafael 
Many thanks for your reply

> -----Original Message-----
> From: rjwysocki@...il.com [mailto:rjwysocki@...il.com] On Behalf Of
> Rafael J. Wysocki
> Sent: 01 April 2017 10:52
> To: zhichang.yuan
> Cc: Rafael J. Wysocki; Yuanzhichang; Rafael J. Wysocki; Catalin
> Marinas; Will Deacon; Rob Herring; Frank Rowand; Bjorn Helgaas; Arnd
> Bergmann; linux-arm-kernel@...ts.infradead.org; Mark Rutland; Brian
> Starkey; Olof Johansson; Lorenzo Pieralisi; Benjamin Herrenschmidt;
> Linux Kernel Mailing List; ACPI Devel Maling List; Linuxarm;
> devicetree@...r.kernel.org; Linux PCI; Corey Minyard; Zou Rongrong;
> John Garry; Gabriele Paoloni; kantyzc@....com; xuwei (O)
> 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.

I guess this is the case for the foreseeable future.

So if my understanding is correct we should leave acpi_indirectio_scan_init()
call in acpi_scan_init() and move its definition under acpi/arm64/ right?

If in future other architectures needs non-pci IO controllers we may consider
to move this to acpi/...

Lorenzo what do you think? Could you have a look at the patchset?

Many thanks

Gab

> 
> Thanks,
> Rafael