[U-Boot] [PATCH v2] AT91: add RTT and GPBR based RTC

[Reinhard Meyer]

Dear Xu, Hong,
>> adds kernel compatible RTC handling to u-boot using the RTT
>> and one GPBRegister
>> ...
>>   arch/arm/include/asm/arch-at91/at91_gpbr.h |   45 +++++++++++++
>>   arch/arm/include/asm/arch-at91/at91_rtt.h  |   36 ++++++++++
>>   drivers/rtc/Makefile                       |    1 +
>>   drivers/rtc/at91sam9.c                     |  100
>
> Some of Atmel's ARM926EJS chips have builtin RTC, for example, SAM9G45 SAM9M10 SAM9RL and new X5 serials.
> May we take this into account at this stage?
>
> We can use big #ifdef to add real RTC support in drivers/rtc/at91sam9.c

I don't think that makes sense, assuming the "real rtc" uses registers
that count like HHMMSS DDMMYY. It would be completely different code.

> - or -
>
> We can rename drivers/rtc/at91sam9.c to , for example, drivers/rtc/at91sam9_rtt.c, and let drivers/rtc/at91sam9.c for the real RTC support.

I'd go with that, and even suggest naming the maybe upcoming "real rtc"
driver at91sam9_rtc.c to give a clearer indication of the different
approaches.

Besides, for LinuX the rtt makes more sense since it directly
counts in seconds since epoch.

Thanks
Reinhard