From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752095AbbCGLrN (ORCPT ); Sat, 7 Mar 2015 06:47:13 -0500 Received: from [212.85.155.42] ([212.85.155.42]:41895 "EHLO atreides.gradator.net" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1750842AbbCGLrK (ORCPT ); Sat, 7 Mar 2015 06:47:10 -0500 Date: Sat, 7 Mar 2015 12:46:08 +0100 From: Sylvain Rochet To: Pavel Machek Cc: Alexandre Belloni , Peter Zijlstra , Mark Rutland , Boris Brezillon , Alessandro Zummo , Mike Turquette , Jason Cooper , "rtc-linux@googlegroups.com" , Len Brown , Greg Kroah-Hartman , "linux-pm@vger.kernel.org" , "Rafael J. Wysocki" , "linux-kernel@vger.kernel.org" , Nicolas Ferre , Wim Van Sebroeck , "linux-serial@vger.kernel.org" , Jean-Christophe Plagniol-Villard , Thomas Gleixner , Jiri Slaby , "linux-arm-kernel@lists.infradead.org" , "linux-watchdog@vger.kernel.org" Message-ID: <20150307114608.GA30011@gradator.net> References: <20150304183809.GD22156@leverpostej> <20150305095306.3db98ac8@bbrezillon> <20150305105308.GA13617@leverpostej> <20150305121723.1da0d016@bbrezillon> <20150305115307.GA14093@leverpostej> <20150307091846.GN23367@worktop.ger.corp.intel.com> <20150307102056.GA28436@gradator.net> <20150307103939.GA17964@amd> <20150307110645.GW3989@piout.net> <20150307112932.GA1372@amd> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="J2SCkAp4GZ/dPZZf" Content-Disposition: inline In-Reply-To: <20150307112932.GA1372@amd> User-Agent: Mutt/1.5.21 (2010-09-15) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: gradator@atreides.gradator.net Subject: Re: [PATCH v2 5/6] watchdog: at91sam9: request the irq with IRQF_NO_SUSPEND X-SA-Exim-Version: 4.2.1 (built Mon, 26 Dec 2011 16:24:06 +0000) X-SA-Exim-Scanned: Yes (on atreides.gradator.net) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --J2SCkAp4GZ/dPZZf Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hello, On Sat, Mar 07, 2015 at 12:29:33PM +0100, Pavel Machek wrote: > On Sat 2015-03-07 12:06:45, Alexandre Belloni wrote: > > On 07/03/2015 at 11:39:39 +0100, Pavel Machek wrote : > > > > The Atmel watchdog can't be stopped once it's started. This is actu= ally=20 > > > > very useful so we can reset if suspend or resume failed, the only= =20 > > > > drawback is that you have to wake up from time to time (e.g. by usi= ng=20 > > > > the RTC/RTT) to clear the watchdog and then go back to sleep ASAP. > > >=20 > > > Yeah. So you do "echo mem > /sys/power/state", and few seconds/minutes > > > after watchdog kills the system. But you did not ask for dead system, > > > you asked for suspend. > > >=20 > > > And while that behaviour is useful for you, I don't think it is > > > exactly useful behaviour, nor it is the behaviour user would expect. > > >=20 > >=20 > > I think you misunderstood, that is exactly the expected behaviour. This > > is hardware defined. Once the watchdog is started, nobody can stop it. > > Trying to change the mode register will result in a reset of the > > SoC. >=20 > Well, it boils down to "what is stronger". Desire to suspend the > system, or desire to reboot the system. >=20 > It is "echo mem > state", not "echo reboot > state". Maybe we should warn the watchdog is enabled and the system is going to=20 reboot if nothing woke-up the system before the watchdog expire, but the=20 maximum watchdog is 16s so it can't get unnoticed during development, I=20 am confident embedded engineers are smart enough to understand what is=20 happening without a displayed warning :-) > > It is documented in the datasheet and any user wanting another behaviour > > is out of luck. >=20 > Actaully, your platform should just refuse to enter suspend-to-RAM > when hw watchdog is enabled. Yeah that's what I said, hardware watchdog or suspend: chose one or use=20 the software watchdog instead or "hack" around the way I am doing ;-) Sylvain --J2SCkAp4GZ/dPZZf Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iEYEARECAAYFAlT65QAACgkQDFub3qtEsS8O0ACfR46nrt7tdgk+tEtgoUM2nDkr B8AAn1YNZvOiEnAxkPdxMaUqAu2Lh1+u =IEKt -----END PGP SIGNATURE----- --J2SCkAp4GZ/dPZZf--