On Thursday, February 16, 2017, Guenter Roeck wrote: > Hmm, ok. Guess I don't have to understand that you can not use the > watchdog driver because of the above, but implementing exactly the same > functionality in a separate driver is ok. > > [ I am sure I am missing something here, so just ignore what I am saying ] Honestly, I don't have a handle on all the latest 'policies and procedures' for all the various subsystems. All I know is that I want to figure out how to execute my 5 lines of code to reset the system when the user types "reboot" on the command line. If this WDT had a timeout longer than 125ms, I would make a real watchdog driver out of it. But at the moment, it just serves as the only way to reset the chip. Historically, this was the only way to reset a SH4 device...and we just lived with that fact. When Renesas moved from SH4 to ARM, a lot of the design teams just kept the same philosophy (and copied the HW blocks they knew already worked) > > > > v2: * changed DT bindings from 'wdt-reset' to 'rza-wdt' * changed > > > > hard coded register values to defines * added msleep to while(1) > > > > loop > > > > > > Sure you can sleep here ? > > > > As per Geert's review: > > > > On Wednesday, February 15, 2017, Geert Uytterhoeven wrote: > > > > + + /* Wait for WDT overflow */ + while (1) > + ; > > > > > > This burns CPU, and thus power, albeit for a very short time. > > > Perhaps add an msleep() to the loop body? > > > > Note that you only have 7.7us before the restart occurs, so probably > > not much sleeping will be going on. > > > Let me rephrase my question. Is it guaranteed that you _can_ sleep in this > function, or in other words that it is guaranteed that interrupts are > enabled ? Hmm, I'm not sure if will actually 'sleep' or not. Regardless, interrupts or not, in 7.7us, the internal reset circuit is going to get triggered and the whole system is going to reboot not matter what is going on. I know Geert's suggestion was in reference to saving power...but in reality it's probably negligible when we are talking about 7.7us. The reboot is going to automatically shut off all the peripherals clocks as well. Chris -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
