From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932701AbcLPJIl (ORCPT ); Fri, 16 Dec 2016 04:08:41 -0500 Received: from wp126.webpack.hosteurope.de ([80.237.132.133]:35316 "EHLO wp126.webpack.hosteurope.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759879AbcLPJIb (ORCPT ); Fri, 16 Dec 2016 04:08:31 -0500 Subject: Re: [PATCH] ARM: dts: Add missing CPU frequencies for Exynos5422/5800 To: Krzysztof Kozlowski , Doug Anderson References: <5220084.l31t5oJbsy@amdc3058> <26ffeee4-ff43-b3d3-3267-5fcbc50e2974@osg.samsung.com> <2340115.HEG9AYUCMD@amdc3058> <20161216073720.GA3489@kozik-lap> Cc: Bartlomiej Zolnierkiewicz , Javier Martinez Canillas , Arjun K V , Kukjin Kim , Rob Herring , Mark Rutland , Russell King , Andreas Faerber , Thomas Abraham , Ben Gamari , linux-samsung-soc , "linux-arm-kernel@lists.infradead.org" , "linux-pm@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Alim From: Markus Reichl Organization: five technologies GmbH Message-ID: <1b6e8d3a-ec7a-db5d-dd0e-ef9d1480f80a@fivetechno.de> Date: Fri, 16 Dec 2016 10:08:07 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: <20161216073720.GA3489@kozik-lap> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-bounce-key: webpack.hosteurope.de;m.reichl@fivetechno.de;1481879311;0475d3e4; X-HE-SMSGID: 1cHoUw-0005WQ-CK Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 16.12.2016 um 08:37 schrieb Krzysztof Kozlowski: > On Thu, Dec 15, 2016 at 04:52:58PM -0800, Doug Anderson wrote: >>> [ I added Arjun to Cc:, maybe he can help in explaining this issue >>> (unfortunately Inderpal's email is no longer working). ] >>> >>> Please also note that on Exynos5422/5800 SoCs the same ARM rail >>> voltage is used for 1.9 GHz & 2.0 GHz OPPs as for the 1.8 GHz one. >>> IOW if the problem exists it is already present in the mainline >>> kernel. >> >> Interesting. In the ChromeOS tree I see significantly higher voltages >> needed... Note that one might naively look at >> . >> >> 1362500, /* L0 2100 */ >> 1312500, /* L1 2000 */ >> >> ..but, amazingly enough those voltages aren't used at all. Surprise! >> >> I believe that the above numbers are actually not used and the ASV >> numbers are used instead. See >> >> >> { 2100000, >> 1350000, 1350000, 1350000, 1350000, 1350000, >> 1337500, 1325000, 1312500, 1300000, 1287500, >> 1275000, 1262500, 1250000, 1237500 }, >> >> I believe that interpretation there is: some bins of the CPU can run >> at 2.1 GHz just fine at 1.25 V but others need up to 1.35V. > > That is definitely the case. One could just look at vendors ASV table > (for 1.9 GHz): > { 1900000, 1300000, 1287500, 1262500, 1237500, 1225000, 1212500, > 1200000, 1187500, 1175000, 1162500, 1150000, > 1137500, 1125000, 1112500, 1112500}, > > The theoretical difference is up to 1.875V! From my experiments I saw > BIN1 chips which should be the same... but some working on 1.2V, some on > 1.225V (@1.9 GHz). I didn't see any requiring higher voltages but that > does not mean that there aren't such... > >> ...so if you're running at 2.1 GHz at 1.25V then perhaps you're just >> running on a CPU from a nice bin? I've been running the proposed frequency/voltage combinations without any stability problems on my XU4, XU3 and even XU3-lite ( I did not delete the nodes on XU3-lite dts) with make -j8 kernel and ssvb-cpuburn. The chips are poorly cooled, especially the XU4 and quickly step down. > > Would be nice to see a dump of PKG_ID and AUX_INFO chipid registers > along with name of tested board. Because the "Tested on XU3" is not > sufficient. If you point me to how to read these values out, I will publish them. > > Best regards, > Krzysztof -- Markus Reichl