From patchwork Mon Apr 27 13:59:48 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Juergen Borleis X-Patchwork-Id: 6281161 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id C1FCA9F2BA for ; Mon, 27 Apr 2015 14:23:32 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 69A15201BB for ; Mon, 27 Apr 2015 14:22:43 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1FF8E2017E for ; Mon, 27 Apr 2015 14:22:14 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1Ymjaq-0000HD-5j; Mon, 27 Apr 2015 14:01:04 +0000 Received: from metis.ext.pengutronix.de ([2001:6f8:1178:4:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1YmjaF-0007YI-4z for linux-arm-kernel@lists.infradead.org; Mon, 27 Apr 2015 14:00:31 +0000 Received: from dude.hi.pengutronix.de ([2001:67c:670:100:1d::7]) by metis.ext.pengutronix.de with esmtps (TLS1.2:RSA_AES_128_CBC_SHA1:128) (Exim 4.80) (envelope-from ) id 1YmjZn-0004u3-TK; Mon, 27 Apr 2015 16:00:00 +0200 Received: from jbe by dude.hi.pengutronix.de with local (Exim 4.84) (envelope-from ) id 1YmjZm-0007L6-KC; Mon, 27 Apr 2015 15:59:58 +0200 From: Juergen Borleis To: linux-kernel@vger.kernel.org Subject: [PATCH 2/6] RTC/i.MX/DryIce: add some background info about the states the machine can be in Date: Mon, 27 Apr 2015 15:59:48 +0200 Message-Id: <1430143192-20667-3-git-send-email-jbe@pengutronix.de> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1430143192-20667-1-git-send-email-jbe@pengutronix.de> References: <1430143192-20667-1-git-send-email-jbe@pengutronix.de> X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::7 X-SA-Exim-Mail-From: jbe@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-arm-kernel@lists.infradead.org X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20150427_070027_434130_D62155BD X-CRM114-Status: GOOD ( 13.58 ) X-Spam-Score: -0.0 (/) Cc: linux-arm-kernel@lists.infradead.org, Alessandro Zummo , Robert Schwebel , kernel@pengutronix.de, rtc-linux@googlegroups.com X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Signed-off-by: Juergen Borleis Signed-off-by: Robert Schwebel [rsc: got NDA clearance from Freescale] --- drivers/rtc/rtc-imxdi.c | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) diff --git a/drivers/rtc/rtc-imxdi.c b/drivers/rtc/rtc-imxdi.c index 0c2a064..6db8d1c 100644 --- a/drivers/rtc/rtc-imxdi.c +++ b/drivers/rtc/rtc-imxdi.c @@ -129,6 +129,49 @@ struct imxdi_dev { struct work_struct work; }; +/* Some background: + * + * The DryIce unit is a complex security/tamper monitor device. To be able do + * its job in a useful manner it runs a bigger statemachine to bring it into + * security/tamper failure state and once again to bring it out of this state. + * + * This unit can be in one of three states: + * + * - "NON-VALID STATE" + * always after the battery power was removed + * - "FAILURE STATE" + * if one of the enabled security events has happened + * - "VALID STATE" + * if the unit works as expected + * + * Everything stops when the unit enters the failure state including the RTC + * counter (to be able to detect the time the security event happened). + * + * The following events (when enabled) let the DryIce unit enter the failure + * state: + * + * - wire-mesh-tamper detect + * - external tamper B detect + * - external tamper A detect + * - temperature tamper detect + * - clock tamper detect + * - voltage tamper detect + * - RTC counter overflow + * - monotonic counter overflow + * - external boot + * + * If we find the DryIce unit in "FAILURE STATE" and the TDCHL cleared, we + * can only detect this state. In this case the unit is completely locked and + * must force a second "SYSTEM POR" to bring the DryIce into the + * "NON-VALID STATE" + "FAILURE STATE" where a recovery is possible. + * If the TDCHL is set in the "FAILURE STATE" we are out of luck. In this case + * a battery power cycle is required. + * + * In the "NON-VALID STATE" + "FAILURE STATE" we can clear the "FAILURE STATE" + * and recover the DryIce unit. By clearing the "NON-VALID STATE" as the last + * task, we bring back this unit into life. + */ + /* * enable a dryice interrupt */