From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751023AbdHaKgN (ORCPT ); Thu, 31 Aug 2017 06:36:13 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:54034 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750790AbdHaKgL (ORCPT ); Thu, 31 Aug 2017 06:36:11 -0400 Subject: Re: [PATCH 2/4] arm: dts: exynos: add exynos5420 cpu capacity-dmips-mhz information To: Krzysztof Kozlowski Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, linux-samsung-soc@vger.kernel.org, linux-renesas-soc@vger.kernel.org, Russell King , Rob Herring , Mark Rutland , Kukjin Kim , Vincent Guittot , Juri Lelli References: <20170830144120.9312-1-dietmar.eggemann@arm.com> <20170830144120.9312-3-dietmar.eggemann@arm.com> <20170830202650.mdlxy2c3uwuq5vde@kozik-lap> From: Dietmar Eggemann Message-ID: <94c1d6c6-655a-2a63-1f01-06ac45990388@arm.com> Date: Thu, 31 Aug 2017 11:36:07 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170830202650.mdlxy2c3uwuq5vde@kozik-lap> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 30/08/17 21:26, Krzysztof Kozlowski wrote: > On Wed, Aug 30, 2017 at 03:41:18PM +0100, Dietmar Eggemann wrote: >> The following 'capacity-dmips-mhz' dt property values are used: >> >> Cortex-A15: 1024, Cortex-A7: 539 >> >> They have been derived from the cpu_efficiency values: >> >> Cortex-A15: 3891, Cortex-A7: 2048 >> >> by scaling them so that the Cortex-A15s (big cores) use 1024. >> >> The cpu_efficiency values were originally derived from the "Big.LITTLE >> Processing with ARM Cortex™-A15 & Cortex-A7" white paper >> (http://www.cl.cam.ac.uk/~rdm34/big.LITTLE.pdf). Table 1 lists 1.9x >> (3891/2048) as the Cortex-A15 vs Cortex-A7 performance ratio for the >> Dhrystone benchmark. >> >> The following platforms are affected once cpu-invariant accounting >> support is re-connected to the task scheduler: >> >> arndale-octa, peach-pi, peach-pit, smdk5420 >> >> The patch has been tested on Samsung Chromebook 2 13" (peach-pi, Exynos >> 5800). >> >> $ cat /sys/devices/system/cpu/cpu*/cpu_capacity >> 1024 >> 1024 >> 1024 >> 1024 >> 389 >> 389 >> 389 >> 389 > > I am missing something... shouldn't this be 539? Or is it scaled with > the clock-frequency (1 GHz) value? Yeah, the capacity-dmips-mhz dt value of 539 for the little cpus is scaled by 1.3/1.8 (max cpu capacity/ system wide max cpu capacity): 539 * 1.3/1.8 = 389 This max cpu capacity scaling is part of both solutions, the 'cpu capacity-dmips-mhz' and the 'cpu_efficiency/clock-frequency dt property' one. The (original*) cpu capacity on a heterogeneous platform expresses uArch and max cpu frequency differences between the (logical) cpus of the system. * not further reduced by rt and/or irq pressure. [...]