Re: [PATCH 4/4] ACPI PCI slot detection driver
From: Kenji Kaneshige
Date: Fri Mar 14 2008 - 01:42:09 EST
Alex-san, Gary-san and Kristen-san,
Thank you for your explanation.
Ok, I understood what you mean and I agreed both implementations
are legal. Also I explained it to our firmware team, and they
understood your situation.
I don't know which implementation is more popular. But according
to the current score (2 : 1), you win the "majority rule".
Alex-san, could you send me the updated patches? I'll Ack the
patch after adding Fujitsu firmware versions to the DMI list
and testing it.
Kristen-san, as I told you in another thread, we might need
a same fix for acpiphp driver. I'll check it and send the patch.
Thanks,
Kenji Kaneshige
Gary Hade wrote:
Hi Alex/Kenji-san,
Time for my 2 cents.
On Wed, Mar 12, 2008 at 09:24:10PM -0600, Alex Chiang wrote:
Hi Kenji-san,
* Kenji Kaneshige <kaneshige.kenji@xxxxxxxxxxxxxx>:
Hi Alex-san,
On my machine, it is legal to evaluate S1F0._SUN independent of
S1F0._STA because L001._INI has already been evaluated.
It would be helpful to know what Fujitsu's namespace looks like.
If Fujitsu slot objects contain _STA and _INI, then I agree with
Kenji-san -- I definitely need to check _STA before evaluating
_SUN.
Thank you for explanation. Maybe I understood the summary of
implementation of HP firmware. But how to use or where to put _INI
method in the ACPI namespace never becomes reasonable reason why
your driver may ignore _STA before evaluating _SUN.
But in any case, I think both HP and Fujitsu firmware are doing
legal things -- neither firmware is breaking the spec.
My understanding of your explanation so far is:
- evaluating _SUN without checking _STA doesn't cause problem,
from the view point of HP's implementation.
- some IBM machine is doing same as HP
I never think those are reasonable reasons why ignoring _STA
before evaluating _SUN is legal. Am I missing something?
I think the piece that I did not explain clearly is that the spec
does not require checking _STA immediately before _SUN. The spec
says:
- you must check _STA before calling _INI
Agreed.
- _INI must be called to initialize _SUN
Based on my review of ACPI spec 3.0b I would add:
1. For a specific device that has only _STA and _SUN methods,
_SUN can be run and it's results can be trusted irrespective
of the _STA return value.
2. For a specific device that has _STA, _INI, and _SUN methods,
_SUN can be run and it's results can be trusted even if
_INI is not run because the device is absent. If the device
is present and _INI is run then _SUN cannot be run until
after _INI is run.
See ACPI spec 3.0b "6.1.8 _SUN (Slot User Number)" which
says nothing about a required presence of the device.
- _INI is called once, when the table is loaded
Agreed.
On HP's implementation, we do obey those rules. We call _INI on
the PCI bridge during boot, which then initializes the children
SxFy objects. From that point on, it is legal for us to call
_SUN.
The other issue is that the spec does not specify the *semantics*
of _STA. P/IBM firmware engineers think _STA should indicate card
presence,
I checked this on the IBM x3850 and it appears to be true. I
instrumented register_slot() in drivers/pci/hotplug/acpiphp_glue.c
to print _STA and _SUN returns and got the following results with
slot 1 (PCI-X) populated, slot 2 (PCI-X) vacant, slot 3 (PCIe) vacant,
slot 4 (PCIe) populated, slot 5 (PCIe) vacant, and slot 6 (PCIe)
populated. When a card is present _STA returns non-zero status
for all functions, otherwise it returns zero. None of the SxFy
devices have an _INI method.
acpiphp: ACPI Hot Plug PCI Controller Driver version: 0.5
acpiphp_glue: found PCI host-bus bridge with hot-pluggable slots
acpiphp_glue: register_slot: \_SB_.VP02.S1F0 sta=0 sun=1
acpiphp_glue: found ACPI PCI Hotplug slot 1 at PCI 0000:02:01
acpiphp: Slot [1] registered
acpiphp_glue: register_slot: \_SB_.VP02.S1F1 sta=0 sun=1
acpiphp_glue: register_slot: \_SB_.VP02.S1F2 sta=0 sun=1
acpiphp_glue: register_slot: \_SB_.VP02.S1F3 sta=0 sun=1
acpiphp_glue: register_slot: \_SB_.VP02.S1F4 sta=0 sun=1
acpiphp_glue: register_slot: \_SB_.VP02.S1F5 sta=0 sun=1
acpiphp_glue: register_slot: \_SB_.VP02.S1F6 sta=0 sun=1
acpiphp_glue: register_slot: \_SB_.VP02.S1F7 sta=0 sun=1
acpiphp_glue: found PCI host-bus bridge with hot-pluggable slots
acpiphp_glue: register_slot: \_SB_.VP03.S2F0 sta=f sun=2
acpiphp_glue: found ACPI PCI Hotplug slot 2 at PCI 0000:06:01
acpiphp: Slot [2] registered
acpiphp_glue: register_slot: \_SB_.VP03.S2F1 sta=f sun=2
acpiphp_glue: register_slot: \_SB_.VP03.S2F2 sta=f sun=2
acpiphp_glue: register_slot: \_SB_.VP03.S2F3 sta=f sun=2
acpiphp_glue: register_slot: \_SB_.VP03.S2F4 sta=f sun=2
acpiphp_glue: register_slot: \_SB_.VP03.S2F5 sta=f sun=2
acpiphp_glue: register_slot: \_SB_.VP03.S2F6 sta=f sun=2
acpiphp_glue: register_slot: \_SB_.VP03.S2F7 sta=f sun=2
acpiphp_glue: found PCI-to-PCI bridge at PCI 0000:0a:00.0
acpiphp_glue: register_slot: \_SB_.VP04.CALG.E3F0 sta=0 sun=3
acpiphp_glue: found ACPI PCI Hotplug slot 3 at PCI 0000:0b:00
acpiphp: Slot [3] registered
acpiphp_glue: register_slot: \_SB_.VP04.CALG.E3F1 sta=0 sun=3
acpiphp_glue: register_slot: \_SB_.VP04.CALG.E3F2 sta=0 sun=3
acpiphp_glue: register_slot: \_SB_.VP04.CALG.E3F3 sta=0 sun=3
acpiphp_glue: register_slot: \_SB_.VP04.CALG.E3F4 sta=0 sun=3
acpiphp_glue: register_slot: \_SB_.VP04.CALG.E3F5 sta=0 sun=3
acpiphp_glue: register_slot: \_SB_.VP04.CALG.E3F6 sta=0 sun=3
acpiphp_glue: register_slot: \_SB_.VP04.CALG.E3F7 sta=0 sun=3
acpiphp_glue: found PCI-to-PCI bridge at PCI 0000:0f:00.0
acpiphp_glue: register_slot: \_SB_.VP05.CALG.E4F0 sta=f sun=4
acpiphp_glue: found ACPI PCI Hotplug slot 4 at PCI 0000:10:00
acpiphp: Slot [4] registered
acpiphp_glue: register_slot: \_SB_.VP05.CALG.E4F1 sta=f sun=4
acpiphp_glue: register_slot: \_SB_.VP05.CALG.E4F2 sta=f sun=4
acpiphp_glue: register_slot: \_SB_.VP05.CALG.E4F3 sta=f sun=4
acpiphp_glue: register_slot: \_SB_.VP05.CALG.E4F4 sta=f sun=4
acpiphp_glue: register_slot: \_SB_.VP05.CALG.E4F5 sta=f sun=4
acpiphp_glue: register_slot: \_SB_.VP05.CALG.E4F6 sta=f sun=4
acpiphp_glue: register_slot: \_SB_.VP05.CALG.E4F7 sta=f sun=4
acpiphp_glue: found PCI-to-PCI bridge at PCI 0000:14:00.0
acpiphp_glue: register_slot: \_SB_.VP06.CALG.E5F0 sta=0 sun=5
acpiphp_glue: found ACPI PCI Hotplug slot 5 at PCI 0000:15:00
acpiphp: Slot [5] registered
acpiphp_glue: register_slot: \_SB_.VP06.CALG.E5F1 sta=0 sun=5
acpiphp_glue: register_slot: \_SB_.VP06.CALG.E5F2 sta=0 sun=5
acpiphp_glue: register_slot: \_SB_.VP06.CALG.E5F3 sta=0 sun=5
acpiphp_glue: register_slot: \_SB_.VP06.CALG.E5F4 sta=0 sun=5
acpiphp_glue: register_slot: \_SB_.VP06.CALG.E5F5 sta=0 sun=5
acpiphp_glue: register_slot: \_SB_.VP06.CALG.E5F6 sta=0 sun=5
acpiphp_glue: register_slot: \_SB_.VP06.CALG.E5F7 sta=0 sun=5
acpiphp_glue: found PCI-to-PCI bridge at PCI 0000:19:00.0
acpiphp_glue: register_slot: \_SB_.VP07.CALG.E6F0 sta=f sun=6
acpiphp_glue: found ACPI PCI Hotplug slot 6 at PCI 0000:1a:00
acpiphp: Slot [6] registered
acpiphp_glue: register_slot: \_SB_.VP07.CALG.E6F1 sta=f sun=6
acpiphp_glue: register_slot: \_SB_.VP07.CALG.E6F2 sta=f sun=6
acpiphp_glue: register_slot: \_SB_.VP07.CALG.E6F3 sta=f sun=6
acpiphp_glue: register_slot: \_SB_.VP07.CALG.E6F4 sta=f sun=6
acpiphp_glue: register_slot: \_SB_.VP07.CALG.E6F5 sta=f sun=6
acpiphp_glue: register_slot: \_SB_.VP07.CALG.E6F6 sta=f sun=6
acpiphp_glue: register_slot: \_SB_.VP07.CALG.E6F7 sta=f sun=6
acpiphp_glue: Bus 0000:1a has 1 slot
acpiphp_glue: Bus 0000:15 has 1 slot
acpiphp_glue: Bus 0000:10 has 1 slot
acpiphp_glue: Bus 0000:0b has 1 slot
acpiphp_glue: Bus 0000:06 has 1 slot
acpiphp_glue: Bus 0000:02 has 1 slot
acpiphp_glue: Total 6 slots
but Fujitsu firmware engineers think _STA should
indicate slot presence.
I don't think either firmware team is incorrect -- it is simply
the case that the specification was not precise enough, to the
point where separate teams following the same spec came up with
implementations with different behaviors and different semantics.
I believe that we both have compliant, legal firmware.
If one list is shorter than the other, then that should be the
list to put in the kernel, and the default behavior should be
"majority rule".
I don't want to consider "majority rule" before I understand why
ignoring _STA is legal.
On HP and IBM machines, it *is* legal because we *did* call _STA,
then _INI, then _SUN. That is one interpretation of the spec.
On Fujitsu machines, the semantics of _STA are different, and it
is not legal to ignore _STA. That is another interpretation of
the spec.
I am not convinced that this a correct interpretation. I believe
that the ACPI spec indicates that it is legal to call _SUN and
trust it's results no matter what _STA returns. I believe the
only constraint on running _SUN is that it be run after _INI is run
if _INI exists for the same device and _STA for that device
indicates that it should be run.
Gary
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