From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bartlomiej Zolnierkiewicz Subject: Re: [PATCH] ARM: dts: exynos4412-odroid-*: add workaround for CPUfreq/reboot issue Date: Tue, 01 Sep 2015 16:08:36 +0200 Message-ID: <15844858.D7Muz8OFGX@amdc1976> References: <1441112929-6751-1-git-send-email-m.szyprowski@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7Bit Return-path: Received: from mailout4.samsung.com ([203.254.224.34]:58525 "EHLO mailout4.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753264AbbIAOI4 (ORCPT ); Tue, 1 Sep 2015 10:08:56 -0400 Received: from epcpsbgm1new.samsung.com (epcpsbgm1 [203.254.230.26]) by mailout4.samsung.com (Oracle Communications Messaging Server 7.0.5.31.0 64bit (built May 5 2014)) with ESMTP id <0NU000YWL4MUHJ00@mailout4.samsung.com> for linux-samsung-soc@vger.kernel.org; Tue, 01 Sep 2015 23:08:55 +0900 (KST) In-reply-to: Sender: linux-samsung-soc-owner@vger.kernel.org List-Id: linux-samsung-soc@vger.kernel.org To: Krzysztof Kozlowski Cc: Marek Szyprowski , Kukjin Kim , linux-samsung-soc@vger.kernel.org, Tobias Jakobi Hi, On Tuesday, September 01, 2015 10:57:37 PM Krzysztof Kozlowski wrote: > 2015-09-01 22:08 GMT+09:00 Marek Szyprowski : > > Exynos4412-based Odroid boards (X2, U3, U3+) don't reset PMIC > > configuration during hardware reset. This causes serious issues with > > CPUfreq, when ARM voltage is set below 1.0V. When one resets the board > > when CPUfreq selected one of lower Exynos 4412 operating points (for > > example: 200MHz and 0.9V), the bootloader crashes and it is not possible > > s/crashes/hangs/ ? I did not observe a crash but a silent hang. > > > to restart the board without turning power off. > > > > This patch provides a workaround for this issue by increasing the start > > of valid range for vdd_arm regulator from 1.0V. After such change, > > CPUfreq can still use lower operating points, but the voltage won't be > > decreased below 1.0V and as a result it will be possible to reset board > > at any time. > > > > Signed-off-by: Marek Szyprowski > > Do you plan to send the same fix for Trats2 board? Everything above > applies there as well plus suspend is affected. The board cannot > properly resume. > > > --- > > Hello, > > > > This issue was there from the beggining, but I was not able to reproduce > > it. It has been already reported by Tobias in early Feb 2015 > > (http://www.spinics.net/lists/linux-samsung-soc/msg42294.html). > > Recently, after CPUfreq changes (conversion to generic cpufreq dt and > > enabling cpufreq in exynos_defconfig) it was much easier to observe this > > issue. > > > > This workaround lets one still use CPUfreq and avoid unexpect board > > crashes during reboot (both 'standard' and emergency). > > Work-around looks nice and clean. It still allows to use cpufreq and > reduce the energy consumption. The patch should go along with > cpufreq-dt support for Exynos4412 which hopefully would be for v4.3. > If cpufreq-dt for Exynos4412 won't get to v4.3 we can figure out > proper solution, not a work-around. This work-around is needed also for the old exynos-cpufreq driver as the problem was already there on some Odroid setups (please read the mail from February pointed by Marek for details). We don't have a better fix for the time being so I think that it should be merged now regardless of cpufreq-dt changes status. > Anyway for the time being: > Reviewed-by: Krzysztof Kozlowski > > Thanks Marek, > BR Best regards, -- Bartlomiej Zolnierkiewicz Samsung R&D Institute Poland Samsung Electronics