Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965179AbbDUX0V (ORCPT ); Tue, 21 Apr 2015 19:26:21 -0400 Received: from down.free-electrons.com ([37.187.137.238]:43098 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S964973AbbDUX0T (ORCPT ); Tue, 21 Apr 2015 19:26:19 -0400 Date: Wed, 22 Apr 2015 01:26:15 +0200 From: Alexandre Belloni To: Juergen Borleis Cc: linux-kernel@vger.kernel.org, rtc-linux@googlegroups.com, kernel@pengutronix.de, Alessandro Zummo , linux-arm-kernel@lists.infradead.org Subject: Re: [rtc-linux] [PATCH 2nd try] RTC/i.MX/DryICE: add recovery routines to the driver Message-ID: <20150421232615.GD8539@piout.net> References: <1429002716-19821-1-git-send-email-jbe@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1429002716-19821-1-git-send-email-jbe@pengutronix.de> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1555 Lines: 34 Hi, On 14/04/2015 at 11:11:51 +0200, Juergen Borleis wrote : > 2nd try, this time with a cover letter... m( > > The built-in RTC unit on some i.MX SoCs isn't an RTC only. It is also a tamper > monitor unit which can keep some keys. When it does its tamper detection job Does it have more functions? I would say that it also holds some keys but I don't have a handy Freescale representative to contact ;) I'm fine getting that unlocking done in the RTC driver but maybe in the future, it will be necessary to handle that in an MFD driver when adding support for the other functions. > and a tamper violation is detected, this RTC unit locks completely including > the real-time counter. In this state the unit is completely useless. The only > way to bring it out of this locked state is a power on reset. At the next boot > time some flags signals the tamper violation and a specific register access > sequence must be done to finaly bring this unit into life again. Until this is > done, there is no way to use it again as an RTC. > But also without any enabled tamper detection sometimes this unit tends to > lock. And in this case the same steps must be done to bring it into life > again. -- Alexandre Belloni, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/