[PATCH v2] PCI: Add information about describing PCI in ACPI

[PATCH v2] PCI: Add information about describing PCI in ACPI

[Bjorn Helgaas]

Here's another stab at this writeup.  I'd appreciate any comments!

Changes from v1 to v2:
  - Consumer/Producer is defined for Extended Address Space descriptors;
    should be ignored for QWord/DWord/Word Address Space descriptors
  - New arches may use Extended Address Space descriptors in PNP0A03 for
    bridge registers, including ECAM (if the arch adds support for this)
  - Add more details about MCFG and _CBA (Lv's suggestion)
  - Incorporate Rafael's suggestions

---

Bjorn Helgaas (1):
      PCI: Add information about describing PCI in ACPI


 Documentation/PCI/00-INDEX      |    2 
 Documentation/PCI/acpi-info.txt |  180 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 182 insertions(+)
 create mode 100644 Documentation/PCI/acpi-info.txt

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[PATCH v2] PCI: Add information about describing PCI in ACPI

[Bjorn Helgaas]

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Re: [PATCH v2] PCI: Add information about describing PCI in ACPI

[Jon Masters]

On 11/29/2016 04:39 PM, Bjorn Helgaas wrote:

> +New architectures should be able to use "Consumer" Extended Address Space
> +descriptors in the PNP0A03 device for bridge registers, including ECAM,
> +although a strict interpretation of [6] might prohibit this.  Old x86 and
> +ia64 kernels assume all address space descriptors, including "Consumer"
> +Extended Address Space ones, are windows, so it would not be safe to
> +describe bridge registers this way on those architectures.

<snip>

> +[6] PCI Firmware 3.0, sec 4.1.2:

<snip>

Thanks for the revised writeup, Bjorn. It's great. I'm trying to get the
above clarified explicitly in terms of the spec, and in terms of what
other Operating Systems would like to see as general preference.

To your point about second generation ARM (server) systems: we're actually
on generation 3+ now and finally getting to the point where people are
listening. A great many times over the past few years, people have had
to be sat on until they did what was needed. Fortunately, we are going
to finally have upstream kernels (and distros based upon them) that
boot out of the box on compliant hardware and will be able to point
people at the usual "upstream first" messaging we've been pushing.

I had originally fallen for the SoC koolaid that PCIe was not essential,
and was convinced fairly early that this was nonsense. But it has taken
a few years for everyone else to get onto that bandwagon. First you give
them exactly what they know and love (a 1-2 socket Xeon class machine
with lots of PCIe lanes), then you go and fix the design to give them
what they actually need (which logically enumerates as PCIe but isn't) ;)

Jon.


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Re: [PATCH v2] PCI: Add information about describing PCI in ACPI

[Bjorn Helgaas]

On Tue, Dec 13, 2016 at 04:09:39AM -0500, Jon Masters wrote:
> On 11/29/2016 04:39 PM, Bjorn Helgaas wrote:
> 
> > +New architectures should be able to use "Consumer" Extended Address Space
> > +descriptors in the PNP0A03 device for bridge registers, including ECAM,
> > +although a strict interpretation of [6] might prohibit this.  Old x86 and
> > +ia64 kernels assume all address space descriptors, including "Consumer"
> > +Extended Address Space ones, are windows, so it would not be safe to
> > +describe bridge registers this way on those architectures.
> 
> <snip>
> 
> > +[6] PCI Firmware 3.0, sec 4.1.2:
> 
> <snip>
> 
> Thanks for the revised writeup, Bjorn. It's great. I'm trying to get the
> above clarified explicitly in terms of the spec, and in terms of what
> other Operating Systems would like to see as general preference.

Any feedback on this?  I'd like to post a revised version soon for v4.11.

Bjorn

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Re: [PATCH v2] PCI: Add information about describing PCI in ACPI

[Linus Torvalds]

Bjorn, this email was marked as spam, because:

  It has a from address in google.com but has failed google.com's
required tests for authentication

in particular, it looks like you used a non-google smtp server
(kernel.org) to send the email, so there is no DKIM hash (or perhaps
google just uses some other non-standard marker for "this actually
came from google"). So gmail marks it as spam because dmarc fails:

       dmarc=fail (p=REJECT dis=NONE) header.from=google.com

Just to let you know. If you use your google.com email, you do need to
go through the google smtp server.

This may or may not be new - I didn't go and look at old messages of
yours, but it is possible that google.com enabled dmarc/dkim recently.

             Linus

On Tue, Nov 29, 2016 at 1:39 PM, Bjorn Helgaas <bhelgaas@google.com> wrote:
> Here's another stab at this writeup.  I'd appreciate any comments!

Re: [PATCH v2] PCI: Add information about describing PCI in ACPI

[Bjorn Helgaas]

On Tue, Nov 29, 2016 at 03:39:11PM -0800, Linus Torvalds wrote:
> Bjorn, this email was marked as spam, because:
> 
>   It has a from address in google.com but has failed google.com's
> required tests for authentication
> 
> in particular, it looks like you used a non-google smtp server
> (kernel.org) to send the email, so there is no DKIM hash (or perhaps
> google just uses some other non-standard marker for "this actually
> came from google"). So gmail marks it as spam because dmarc fails:
> 
>        dmarc=fail (p=REJECT dis=NONE) header.from=google.com
> 
> Just to let you know. If you use your google.com email, you do need to
> go through the google smtp server.
> 
> This may or may not be new - I didn't go and look at old messages of
> yours, but it is possible that google.com enabled dmarc/dkim recently.

Argh, thanks for letting me know.  Looks like I've had this broken for a
long time, but I didn't notice.  I think I have it fixed so git will record
the author as bhelgaas@google.com, but git/stgit will send email from
helgaas@kernel.org via the kernel.org smtp server.

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Re: [PATCH v2] PCI: Add information about describing PCI in ACPI

[Bjorn Helgaas]

On Tue, Nov 29, 2016 at 03:39:48PM -0600, Bjorn Helgaas wrote:
> Here's another stab at this writeup.  I'd appreciate any comments!
> 
> Changes from v1 to v2:
>   - Consumer/Producer is defined for Extended Address Space descriptors;
>     should be ignored for QWord/DWord/Word Address Space descriptors
>   - New arches may use Extended Address Space descriptors in PNP0A03 for
>     bridge registers, including ECAM (if the arch adds support for this)
>   - Add more details about MCFG and _CBA (Lv's suggestion)
>   - Incorporate Rafael's suggestions
> 
> ---
> 
> Bjorn Helgaas (1):
>       PCI: Add information about describing PCI in ACPI
> 
> 
>  Documentation/PCI/00-INDEX      |    2 
>  Documentation/PCI/acpi-info.txt |  180 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 182 insertions(+)
>  create mode 100644 Documentation/PCI/acpi-info.txt

It's very late in the cycle, but I'm considering trying to squeeze
this into v4.9 on the grounds that:

  - It's only a documentation change and can't break anything, and

  - Distributing it more widely may help the arm64 firmware ecosystem

But I don't want to disseminate misleading or incorrect information,
so if it needs clarification or wordsmithing, or even just maturation,
I'll wait until v4.10.

The Consumer/Producer stuff, in particular, doesn't seem 100% settled
yet.  Your thoughts, and especially your improvements, are welcome!

Bjorn

Re: [PATCH v2] PCI: Add information about describing PCI in ACPI

[Rafael J. Wysocki]

On Thursday, December 01, 2016 04:36:04 PM Bjorn Helgaas wrote:
> On Tue, Nov 29, 2016 at 03:39:48PM -0600, Bjorn Helgaas wrote:
> > Here's another stab at this writeup.  I'd appreciate any comments!
> > 
> > Changes from v1 to v2:
> >   - Consumer/Producer is defined for Extended Address Space descriptors;
> >     should be ignored for QWord/DWord/Word Address Space descriptors
> >   - New arches may use Extended Address Space descriptors in PNP0A03 for
> >     bridge registers, including ECAM (if the arch adds support for this)
> >   - Add more details about MCFG and _CBA (Lv's suggestion)
> >   - Incorporate Rafael's suggestions
> > 
> > ---
> > 
> > Bjorn Helgaas (1):
> >       PCI: Add information about describing PCI in ACPI
> > 
> > 
> >  Documentation/PCI/00-INDEX      |    2 
> >  Documentation/PCI/acpi-info.txt |  180 +++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 182 insertions(+)
> >  create mode 100644 Documentation/PCI/acpi-info.txt
> 
> It's very late in the cycle, but I'm considering trying to squeeze
> this into v4.9 on the grounds that:
> 
>   - It's only a documentation change and can't break anything, and
> 
>   - Distributing it more widely may help the arm64 firmware ecosystem
> 
> But I don't want to disseminate misleading or incorrect information,
> so if it needs clarification or wordsmithing, or even just maturation,
> I'll wait until v4.10.
> 
> The Consumer/Producer stuff, in particular, doesn't seem 100% settled
> yet.  Your thoughts, and especially your improvements, are welcome!

Well, what's the drawback if it doesn't go into 4.9?

Thanks,
Rafael

Re: [PATCH v2] PCI: Add information about describing PCI in ACPI

[Bjorn Helgaas]

On Thu, Dec 01, 2016 at 11:37:39PM +0100, Rafael J. Wysocki wrote:
> On Thursday, December 01, 2016 04:36:04 PM Bjorn Helgaas wrote:
> > On Tue, Nov 29, 2016 at 03:39:48PM -0600, Bjorn Helgaas wrote:
> > > Here's another stab at this writeup.  I'd appreciate any comments!
> > > 
> > > Changes from v1 to v2:
> > >   - Consumer/Producer is defined for Extended Address Space descriptors;
> > >     should be ignored for QWord/DWord/Word Address Space descriptors
> > >   - New arches may use Extended Address Space descriptors in PNP0A03 for
> > >     bridge registers, including ECAM (if the arch adds support for this)
> > >   - Add more details about MCFG and _CBA (Lv's suggestion)
> > >   - Incorporate Rafael's suggestions
> > > 
> > > ---
> > > 
> > > Bjorn Helgaas (1):
> > >       PCI: Add information about describing PCI in ACPI
> > > 
> > > 
> > >  Documentation/PCI/00-INDEX      |    2 
> > >  Documentation/PCI/acpi-info.txt |  180 +++++++++++++++++++++++++++++++++++++++
> > >  2 files changed, 182 insertions(+)
> > >  create mode 100644 Documentation/PCI/acpi-info.txt
> > 
> > It's very late in the cycle, but I'm considering trying to squeeze
> > this into v4.9 on the grounds that:
> > 
> >   - It's only a documentation change and can't break anything, and
> > 
> >   - Distributing it more widely may help the arm64 firmware ecosystem
> > 
> > But I don't want to disseminate misleading or incorrect information,
> > so if it needs clarification or wordsmithing, or even just maturation,
> > I'll wait until v4.10.
> > 
> > The Consumer/Producer stuff, in particular, doesn't seem 100% settled
> > yet.  Your thoughts, and especially your improvements, are welcome!
> 
> Well, what's the drawback if it doesn't go into 4.9?

Only that it's not as easily accessible.  ARM64 ACPI firmware is brand
new.  Neither the firmware nor the kernel developers, nor even the
hardware designers, have the benefit of all the x86/ia64 history, so I
wrote this to try to come to a common understanding of what Linux
expects.

The first generation of ARM64 hardware is already in the field, and it
has teething problems in hardware, firmware, and kernel.  For example,
the current MCFG quirk situation: the ECAM hardware doesn't work quite
per spec, the ACPI firmware doesn't describe the address space
completely, and we don't really have consensus on how the firmware
should communicate register space to the kernel.

We're hoping the second generation can fix some of these problems, and
I think this is the time to try to influence that.

Bjorn

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Re: [PATCH v2] PCI: Add information about describing PCI in ACPI

[Rafael J. Wysocki]

On Fri, Dec 2, 2016 at 12:27 AM, Bjorn Helgaas <helgaas@kernel.org> wrote:
> On Thu, Dec 01, 2016 at 11:37:39PM +0100, Rafael J. Wysocki wrote:
>> On Thursday, December 01, 2016 04:36:04 PM Bjorn Helgaas wrote:
>> > On Tue, Nov 29, 2016 at 03:39:48PM -0600, Bjorn Helgaas wrote:
>> > > Here's another stab at this writeup.  I'd appreciate any comments!
>> > >
>> > > Changes from v1 to v2:
>> > >   - Consumer/Producer is defined for Extended Address Space descriptors;
>> > >     should be ignored for QWord/DWord/Word Address Space descriptors
>> > >   - New arches may use Extended Address Space descriptors in PNP0A03 for
>> > >     bridge registers, including ECAM (if the arch adds support for this)
>> > >   - Add more details about MCFG and _CBA (Lv's suggestion)
>> > >   - Incorporate Rafael's suggestions
>> > >
>> > > ---
>> > >
>> > > Bjorn Helgaas (1):
>> > >       PCI: Add information about describing PCI in ACPI
>> > >
>> > >
>> > >  Documentation/PCI/00-INDEX      |    2
>> > >  Documentation/PCI/acpi-info.txt |  180 +++++++++++++++++++++++++++++++++++++++
>> > >  2 files changed, 182 insertions(+)
>> > >  create mode 100644 Documentation/PCI/acpi-info.txt
>> >
>> > It's very late in the cycle, but I'm considering trying to squeeze
>> > this into v4.9 on the grounds that:
>> >
>> >   - It's only a documentation change and can't break anything, and
>> >
>> >   - Distributing it more widely may help the arm64 firmware ecosystem
>> >
>> > But I don't want to disseminate misleading or incorrect information,
>> > so if it needs clarification or wordsmithing, or even just maturation,
>> > I'll wait until v4.10.
>> >
>> > The Consumer/Producer stuff, in particular, doesn't seem 100% settled
>> > yet.  Your thoughts, and especially your improvements, are welcome!
>>
>> Well, what's the drawback if it doesn't go into 4.9?
>
> Only that it's not as easily accessible.  ARM64 ACPI firmware is brand
> new.  Neither the firmware nor the kernel developers, nor even the
> hardware designers, have the benefit of all the x86/ia64 history, so I
> wrote this to try to come to a common understanding of what Linux
> expects.
>
> The first generation of ARM64 hardware is already in the field, and it
> has teething problems in hardware, firmware, and kernel.  For example,
> the current MCFG quirk situation: the ECAM hardware doesn't work quite
> per spec, the ACPI firmware doesn't describe the address space
> completely, and we don't really have consensus on how the firmware
> should communicate register space to the kernel.
>
> We're hoping the second generation can fix some of these problems, and
> I think this is the time to try to influence that.

Well, I would be super-careful if I were you, then. :-)

I'm not sure if squeezing it into 4.9.0 buys you anything here.  If
you get it into 4.10-rc, you can request -stable to pick it up (at
least in principle) and then it will show up in 4.9.y at one point
which should suffice I suppose?

Thanks,
Rafael

Re: [PATCH v2] PCI: Add information about describing PCI in ACPI

[Bjorn Helgaas]

On Fri, Dec 02, 2016 at 01:28:50AM +0100, Rafael J. Wysocki wrote:
> On Fri, Dec 2, 2016 at 12:27 AM, Bjorn Helgaas <helgaas@kernel.org> wrote:
> > On Thu, Dec 01, 2016 at 11:37:39PM +0100, Rafael J. Wysocki wrote:
> >> On Thursday, December 01, 2016 04:36:04 PM Bjorn Helgaas wrote:
> >> > On Tue, Nov 29, 2016 at 03:39:48PM -0600, Bjorn Helgaas wrote:
> >> > > Here's another stab at this writeup.  I'd appreciate any comments!
> >> > >
> >> > > Changes from v1 to v2:
> >> > >   - Consumer/Producer is defined for Extended Address Space descriptors;
> >> > >     should be ignored for QWord/DWord/Word Address Space descriptors
> >> > >   - New arches may use Extended Address Space descriptors in PNP0A03 for
> >> > >     bridge registers, including ECAM (if the arch adds support for this)
> >> > >   - Add more details about MCFG and _CBA (Lv's suggestion)
> >> > >   - Incorporate Rafael's suggestions
> >> > >
> >> > > ---
> >> > >
> >> > > Bjorn Helgaas (1):
> >> > >       PCI: Add information about describing PCI in ACPI
> >> > >
> >> > >
> >> > >  Documentation/PCI/00-INDEX      |    2
> >> > >  Documentation/PCI/acpi-info.txt |  180 +++++++++++++++++++++++++++++++++++++++
> >> > >  2 files changed, 182 insertions(+)
> >> > >  create mode 100644 Documentation/PCI/acpi-info.txt
> >> >
> >> > It's very late in the cycle, but I'm considering trying to squeeze
> >> > this into v4.9 on the grounds that:
> >> >
> >> >   - It's only a documentation change and can't break anything, and
> >> >
> >> >   - Distributing it more widely may help the arm64 firmware ecosystem
> >> >
> >> > But I don't want to disseminate misleading or incorrect information,
> >> > so if it needs clarification or wordsmithing, or even just maturation,
> >> > I'll wait until v4.10.
> >> >
> >> > The Consumer/Producer stuff, in particular, doesn't seem 100% settled
> >> > yet.  Your thoughts, and especially your improvements, are welcome!
> >>
> >> Well, what's the drawback if it doesn't go into 4.9?
> >
> > Only that it's not as easily accessible.  ARM64 ACPI firmware is brand
> > new.  Neither the firmware nor the kernel developers, nor even the
> > hardware designers, have the benefit of all the x86/ia64 history, so I
> > wrote this to try to come to a common understanding of what Linux
> > expects.
> >
> > The first generation of ARM64 hardware is already in the field, and it
> > has teething problems in hardware, firmware, and kernel.  For example,
> > the current MCFG quirk situation: the ECAM hardware doesn't work quite
> > per spec, the ACPI firmware doesn't describe the address space
> > completely, and we don't really have consensus on how the firmware
> > should communicate register space to the kernel.
> >
> > We're hoping the second generation can fix some of these problems, and
> > I think this is the time to try to influence that.
> 
> Well, I would be super-careful if I were you, then. :-)
> 
> I'm not sure if squeezing it into 4.9.0 buys you anything here.  If
> you get it into 4.10-rc, you can request -stable to pick it up (at
> least in principle) and then it will show up in 4.9.y at one point
> which should suffice I suppose?

You're right, there's no real hurry, and the rate of change is a good
indication that we need to let things settle out for a while.

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