From mboxrd@z Thu Jan 1 00:00:00 1970 From: George Cherian Subject: Re: [PATCH 0/2] Make cppc acpi driver aware of pcc subspace ids Date: Tue, 4 Apr 2017 16:23:44 +0530 Message-ID: <58E37B38.2030204@caviumnetworks.com> References: <1490941442-11954-1-git-send-email-george.cherian@cavium.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Hoan Tran , "Prakash, Prashanth" Cc: George Cherian , linux acpi , lkml , devel@acpica.org, Ashwin Chaugule , "Rafael J. Wysocki" , Len Brown , Jassi Brar , Robert Moore , Lv Zheng List-Id: linux-acpi@vger.kernel.org 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 > 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 >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-acpi" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html