From mboxrd@z Thu Jan 1 00:00:00 1970 From: gradator@gradator.net (Sylvain Rochet) Date: Sat, 7 Mar 2015 12:46:08 +0100 Subject: [PATCH v2 5/6] watchdog: at91sam9: request the irq with IRQF_NO_SUSPEND In-Reply-To: <20150307112932.GA1372@amd> 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> Message-ID: <20150307114608.GA30011@gradator.net> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 actually > > > > very useful so we can reset if suspend or resume failed, the only > > > > drawback is that you have to wake up from time to time (e.g. by using > > > > the RTC/RTT) to clear the watchdog and then go back to sleep ASAP. > > > > > > 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. > > > > > > 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. > > > > > > > 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. > > Well, it boils down to "what is stronger". Desire to suspend the > system, or desire to reboot the system. > > It is "echo mem > state", not "echo reboot > state". Maybe we should warn the watchdog is enabled and the system is going to reboot if nothing woke-up the system before the watchdog expire, but the maximum watchdog is 16s so it can't get unnoticed during development, I am confident embedded engineers are smart enough to understand what is happening without a displayed warning :-) > > It is documented in the datasheet and any user wanting another behaviour > > is out of luck. > > 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 the software watchdog instead or "hack" around the way I am doing ;-) Sylvain -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 198 bytes Desc: Digital signature URL: