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Date:   Tue, 4 Apr 2017 16:23:44 +0530
From:   George Cherian <gcherian@...iumnetworks.com>
To:     Hoan Tran <hotran@....com>,
        "Prakash, Prashanth" <pprakash@...eaurora.org>
Cc:     George Cherian <george.cherian@...ium.com>,
        linux acpi <linux-acpi@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>, devel@...ica.org,
        Ashwin Chaugule <ashwin.chaugule@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Jassi Brar <jassisinghbrar@...il.com>,
        Robert Moore <robert.moore@...el.com>,
        Lv Zheng <lv.zheng@...el.com>
Subject: Re: [PATCH 0/2] Make cppc acpi driver aware of pcc subspace ids

Hi Hoan/Prashanth,


On 04/03/2017 11:20 PM, Hoan Tran wrote:
> Hi George,
>
> On Mon, Apr 3, 2017 at 9:44 AM, Prakash, Prashanth
> <pprakash@...eaurora.org> wrote:
>> Hi George,
>>
>> On 3/31/2017 12:24 AM, George Cherian wrote:
>>> The current cppc acpi driver works with only one pcc subspace id.
>>> It maintains and registers only one pcc channel even if the acpi table has
>>> different pcc subspace ids. The series tries to address the same by making
>>> cppc acpi driver aware of multiple possible pcc subspace ids.
>> The current ACPI 6.1 spec restricts the CPPC to a single PCC subspace. See section:
>> 8.4.7.1.9 Using PCC Registers, which states "If the PCC register space is used, all PCC
>> registers must be defined to be in the same subspace."
>
> Agreed with Prashanth, beside of that, spec also says "To amortize the
> cost of PCC transactions, OSPM should read or
> write all PCC registers via a single read or write command when possible."

Yes indeed the spec says so but it was not at all a scalable solution 
when platform has more number of CPU's and CPU domains. That is why we 
took this approach.

>
> Thanks
> Hoan
>
>>
>> --
>> Thanks,
>> Prashanth
>> --
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