Re: [PATCH v5 0/1] ARM64: ACPI: Update documentation for latest specification version

From: Al Stone
Date: Thu May 26 2016 - 18:31:33 EST

On 05/17/2016 10:30 AM, Al Stone wrote:
> On 05/16/2016 05:44 PM, Alexey Klimov wrote:
>> On Mon, May 2, 2016 at 09:19 PM, Al Stone wrote:
>>> On 04/25/2016 03:21 PM, Al Stone wrote:
>>>> The ACPI 6.1 specification was recently released at the end of January
>>>> 2016, but the arm64 kernel documentation for the use of ACPI was written
>>>> for the 5.1 version of the spec. There were significant additions to the
>>>> spec that had not yet been mentioned -- for example, the 6.0 mechanisms
>>>> added to make it easier to define processors and low power idle states,
>>>> as well as the 6.1 addition allowing regular interrupts (not just from
>>>> GPIO) be used to signal ACPI general purpose events.
>>>> This patch reflects going back through and examining the specs in detail
>>>> and updating content appropriately. Whilst there, a few odds and ends of
>>>> typos were caught as well. This brings the documentation up to date with
>>>> ACPI 6.1 for arm64.
>>>> Changes for v5:
>>>> -- Miscellaneous typos and corrections (Lorenzo Pieralisi)
>>>> -- Add linux-acpi@ ML to the distribution list (Alexey Klimov)
>>>> -- Corrections to CPPC information (Alexey Klimov)
>>>> -- ACK from Lorenzo Pieralisi
>>>> -- Updated bibliographic info (Al Stone)
>>>> Changes for v4:
>>>> -- Clarify that IORT can sometimes be optional (Jon Masters).
>>>> -- Remove "Use as needed" descriptions of ACPI objects; they provide
>>>> no substantive information and doing so simplifies maintenance of
>>>> this document over time. These have been replaced with a simpler
>>>> notice that states that unless otherwise noted, do what the ACPI
>>>> specification says is needed.
>>>> -- Corrected the _OSI object usage recommendation; it described kernel
>>>> behavior that does not exist (Al Stone).
>>>> Changes for v3:
>>>> -- Clarify use of _LPI/_RDI (Vikas Sajjan)
>>>> -- Whitespace cleanup as pointed out by checkpatch
>>>> Changes for v2:
>>>> -- Clean up white space (Harb Abdulhahmid)
>>>> -- Clarification on _CCA usage (Harb Abdulhamid)
>>>> -- IORT moved to required from recommended (Hanjun Guo)
>>>> -- Clarify IORT description (Hanjun Guo)
>>>> Al Stone (1):
>>>> ARM64: ACPI: Update documentation for latest specification version
>>>> Documentation/arm64/acpi_object_usage.txt | 343 ++++++++++++++++--------------
>>>> Documentation/arm64/arm-acpi.txt | 40 ++--
>>>> 2 files changed, 213 insertions(+), 170 deletions(-)
>>> Ping? If there are no further comments, can this be pulled in through
>>> either the documentation or arm64 tree?
>>> Thanks.
>> Hi Al,
>> sorry for delay.
>> CPPC and PCC corrections look fine. Thanks.
>> This comment is not to block your patch (maybe some to-do):
>> I greped sources and your patch and I don't see description of _PSD object.
>> This P-state dependancy object is optional but it's presense and correct data
>> are extremely useful for CPPC and can potentially descrease number of performance
>> changing requests.
>> ACPI spec in section about CPPC tells that it may use _PSD (page 503 if I remember
>> correctly) to specify domain belongings of CPUs.
>> You may consider to add description of _PSD object later.
>> Best regards,
>> Alexey.
> Hrm. Thanks, Alexey. I'll take a look. _PSD may be in one of
> the gray areas where we expect people to read the spec and follow
> it properly, but it may make sense to be very explicit about what
> they need to do to use it properly. Perhaps this would make a good
> FWTS test, too.

Yet another ping...

Just in case it is not clear, Alexey's comment and my reply here are
things that *might* need to be done in the future. This version of the
patch I believe is sufficient for now, based on the comments received.

Lorenzo has ACKd; Hanjun has reviewed. Do I need Will and/or Catalin
to ACK? Any others?

Al Stone
Software Engineer
Red Hat, Inc.