Messages in this thread | | | Subject | Re: [PATCH v2 3/4] dt-bindings: watchdog: da9062: add watchdog timeout mode | From | Andrej Picej <> | Date | Wed, 1 Dec 2021 07:42:44 +0100 |
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On 30. 11. 21 18:46, Adam Thomson wrote: > On 30 November 2021 16:40, Guenter Roeck wrote: > >>>> Why does it need a value ? Why not just bool ? >>> >>> One argument might be that if the property isn't provided then the OTP >>> configured value can persist without needing a FW change around this DT >> binding. >>> >>> My belief though is that the majority of users would have this property set to 0 >>> by default in OTP, so a boolean would be OK I think here to enable watchdog >>> shutdown. >>> >> >> Sorry, you lost me. >> dlg,wdt-sd = <0>; >> is the current situation, and identical to not having the property in >> the first place. >> dlg,wdt-sd = <1>; >> is new. I don't see the difference to >> dlg,wdt-sd; >> vs. not having the property at all (which is, again, the current situation). >> Since it has to be backward compatible, >> dlg,wdt-sd = <0>; >> will always be identical to not having the property at all. >> I can not find a situation where an integer would have any benefits over a >> boolean. > > So if you have a binary DT binding, it's either there or it isn't which implies > the bit to be set to 0/1 in this case. If you have a binding which has a value, > there can be 3 outcomes in this discussion: > > 1) Binding = 0, bit is set to 0 > 2) Binding = 1, bit is set to 1 > 3) Binding NOT present in DT, OTP default value in HW remains untouched > > Say a platform updates to a later kernel version, but sticks with existing DT > FW (i.e. the new boolean binding isn't present in FW), then the following could > happen: > > 1) OTP for DA9061/2 has this bit set to 1, system expectation is that watchdog > triggers SHUTDOWN. > 2) New driver checks existance of 'dlg,wdt-sd' but it's obviously not there so > assumes the bit should be set to 0 and does so > 3) When the watchdog fires, it will no longer trigger SHUTDOWN but instead > POWER-DOWN due to binary handling of new boolean binding. >
This was my thinking exactly. I also first thought about boolean value, but I then moved to the integer value of 0 or 1 after checking the OTP default for this bit. The da9062 I'm working with has the bit set to 1 by default.
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