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From: John Garry <john.garry@huawei.com>
To: Sudeep Holla <sudeep.holla@arm.com>
Cc: <rjw@rjwysocki.net>, <lenb@kernel.org>, <jeremy.linton@arm.com>,
	<arnd@arndb.de>, <olof@lixom.net>, <linux-kernel@vger.kernel.org>,
	<linux-acpi@vger.kernel.org>, <guohanjun@huawei.com>,
	<gregkh@linuxfoundation.org>,
	Jonathan Cameron <Jonathan.Cameron@huawei.com>,
	wanghuiqiang <wanghuiqiang@huawei.com>
Subject: Re: [PATCH RFC 1/2] ACPI/PPTT: Add acpi_pptt_get_package_info() API
Date: Tue, 28 Jan 2020 14:04:19 +0000	[thread overview]
Message-ID: <60c79aaa-4c49-71b1-11be-8e41a6bf3c1d@huawei.com> (raw)
In-Reply-To: <20200128123415.GB36168@bogus>

On 28/01/2020 12:34, Sudeep Holla wrote:

Hi Sudeep,

> On Tue, Jan 28, 2020 at 07:14:18PM +0800, John Garry wrote:
>> The ACPI PPTT ID structure (see 6.2 spec, section 5.2.29.3) allows the
>> vendor to provide an identifier (or vendor specific part number) for a
>> particular processor hierarchy node structure. That may be a processor
>> identifier for a processor node, or some chip identifier for a processor
>> package node.
>>
> 
> Unfortunately, there were plans to deprecate this in favour of the new
> SOC_ID SMCCC API[1]. I am not sure if you or anyone in your company have
> access to UEFI ASWG mantis where you can look for the ECR for the PPTT
> Type 2 deprecation.

I wasn't aware and I can't get access...

Personally I would rather PPTT ID structure have a fixed field 
definition in future spec versions, rather than deprecate.

 From checking here, nobody has even used it (properly) for processor 
package nodes:
https://github.com/tianocore/edk2-platforms/tree/master/Platform

  I understand it's not ideal, but we need to converge,
> please take a look at both before further discussion.

I can only check the SMCCC extension which you pointed me at.

> 
> I personally would not prefer to add the support when I know it is getting
> deprecated. I am not sure on kernel community policy on the same.

So I need a generic solution for this, as my userspace tool requires a 
generic solution.

> 
> 
> [...]
> 
>>
>> The ID structure table has a number of fields, which are left open to
>> interpretation per implementation. However the spec does provide reference
>> examples of how the fields could be used. As such, just provide the
>> table fields directly in the API, which the caller may interpret (probably
>> as per spec example).
>>
> 
> The "open for interpretation" part is why it's not being favoured anymore
> by silicon vendors as OEM/ODMs can override the same.
> 
>> https://lore.kernel.org/linux-arm-kernel/1579876505-113251-6-git-send-email-john.garry@huawei.com/
>>
> Ah, there's already quite a lot of dependency built for this feature :(

Not really. It's only an RFC ATM, and my requirement is a sysfs file to 
read the SoC id(s) (under ACPI FW). So I would still expect to be able 
to support this from the SMCCC extension method.

> 
> --
> Regards,
> Sudeep
> 
> [1] https://developer.arm.com/docs/den0028/c
> .
> 

Cheers,
John


  reply	other threads:[~2020-01-28 14:06 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-28 11:14 [PATCH RFC 0/2] Add basic generic ACPI soc driver John Garry
2020-01-28 11:14 ` [PATCH RFC 1/2] ACPI/PPTT: Add acpi_pptt_get_package_info() API John Garry
2020-01-28 12:34   ` Sudeep Holla
2020-01-28 14:04     ` John Garry [this message]
2020-01-28 14:54       ` Sudeep Holla
2020-01-29 11:03         ` John Garry
2020-01-30 11:23     ` Sudeep Holla
2020-01-30 16:12       ` John Garry
2020-01-30 17:41         ` Sudeep Holla
2020-01-31 10:58           ` John Garry
2020-01-28 11:14 ` [PATCH RFC 2/2] soc: Add a basic ACPI generic driver John Garry
2020-01-28 11:56   ` Greg KH
2020-01-28 13:33     ` John Garry
2020-01-28 12:50   ` Arnd Bergmann
2020-01-28 14:46     ` John Garry
2020-01-28 15:20   ` Sudeep Holla
2020-01-28 15:59     ` John Garry
2020-01-28 16:17       ` Sudeep Holla
2020-01-28 17:51   ` Olof Johansson
2020-01-28 18:22     ` John Garry
2020-01-28 19:11       ` Rafael J. Wysocki
2020-01-28 19:28         ` John Garry
2020-01-28 22:30           ` Rafael J. Wysocki
2020-01-29 10:27             ` John Garry
2020-01-28 20:06       ` Olof Johansson
2020-01-29  9:58         ` John Garry
2020-01-28 16:56 ` [PATCH RFC 0/2] Add basic generic ACPI soc driver Jeremy Linton
2020-01-28 17:28   ` John Garry
2020-01-28 19:04     ` Jeremy Linton
2020-01-28 20:07       ` John Garry

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