Re: [PATCH 1/3] ARM: dts: omap5-board-common: enable rtc and charging of backup battery

[Keerthy <a0393675@ti.com>]

On Thursday 14 January 2016 04:02 AM, Nishanth Menon wrote:
> On 01/13/2016 01:40 PM, Tony Lindgren wrote:
>
>> Anyways, considering what's been discussed, after the minimal RTC fix
>> we could also add code to allow the TWL driver optionally configure the
>> GPIO. This way the TWL driver could also check the GPIO state in case
>> some out-of-our-control mystery software goes tweak the msecure pin
>> state.
>
> I dont even know how that will work:
> If you are using MSECURE as it is intended to be, then you'd mux it to
> msecure, which means that GPIO read is just a waste of time - you dont
> even mux it to external world. Now, some SoCs like DRA7 has input lines
> always connected. even assuming this is for such a case:
> a) when you are running linux, you are already in nonsecure - it needs
> no read of MSECURE GPIO to figure that out.
> b)  when you are in secure world, Linux wont be running either.
>
> Reading from GPIO is just misguided in my opinion. firewalls are not
> reconfigured, and muxes are usually done a single time.
>
>   Or the RTC driver could just check that the bits really change
>> after= writing them. Then we would at least know things are not working
>> right for the TWL related RTC drivers.
>
> that is reasonable to check, but just a overhead - anyways, just
> isolated to palmas-rtc.. fail reason maynot always be issues with
> MSECURE mux.. it could be very well be 32k clk fail etc.. but yeah -
> that might give a hint that there is an issue..
>

IIRC without configuring the mux mode of gpio234 to msecure mode we were 
unable to write to the rtc registers. Hence configured it one time at boot.