[PATCH v2 0/3] Extend rtc-armada38x support for Armada 7K/8K

Gregory CLEMENT
2017-02-20T17:43:32Z

Hi Alexandre,

On lun., f?vr. 20 2017, Alexandre Belloni <alexandre.belloni@free-electrons.com> wrote:

> On 20/02/2017 at 18:06:11 +0100, Gregory CLEMENT wrote:
>> On ven., f?vr. 17 2017, Gregory CLEMENT <gregory.clement@free-electrons.com> wrote:
>>
>> > The Armada 7K/8K SoCs use the same RTC IP than the Armada 38x. However
>> > the SOC integration differs in 2 points:
>> > - MBUS bridge timing initialization
>> > - IRQ configuration at SoC level
>> >
>> > This patch set extends the driver support to these SoCs family.
>> >
>> > In this second version the device tree was updated allowing to use the
>> > RTC on Armada 80x0 SoCs. Indeed on the Armada 80x0, the RTC clock in
>> > CP master is not connected (by package) to the oscillator. So this one
>> > is disabled for the Armada 8020 and the Armada 8040. On these SoCs it
>> > will be the RTC clock in CP slave connected to the oscillator which
>> > will be used.
>>
>> I saw on IRC than Russell managed to have a more coherent date with this
>> series on his 8040 based board. For the record, as the U-Boot on this
>> board didn't provide a "date reset" command for the RTC located on CP
>> slave, then Russell needed to do the following:
>>
>> devmem2 0xf428401c w 0
>> devmem2 0xf4284018 w 0x2000
>
> The question being what does that do and whether it could be done in the
> driver instead.

The first time the RTC is powered up it needed to be reset. It is the
purpose of these 2 lines. As it should be done only one time when a the
RTC is powered of the first time it was chosen to be done in the
bootloader.

Maybe later it could be part of the kernel, as an optional parameter for
instance, but currently I don't know if there is more involved when
resetting the RTC.

Gregory

>
> --
> Alexandre Belloni, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com

--
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.