Re: [PATCH 5/5] rtc: at91sam9: add DT bindings documentation

Johan Hovold
2014-09-10T15:09:03Z

On Wed, Sep 10, 2014 at 03:20:19PM +0200, Boris BREZILLON wrote:
> On Wed, 10 Sep 2014 14:14:24 +0200
> Johan Hovold <johan@kernel.org> wrote:

> > This does not describe the hardware, but rather a specific software
> > configuration.
> >
> > The RTT is first of all not an RTC (although it can be used as one in a
> > specific software configuration). And the second register resource above
> > is not an RTT register, but a general-purpose backup register could be
> > used for other purposes (which register to use is currently configurable
> > for legacy booting using CONFIG_RTC_DRV_AT91SAM9_GPBR).
>
> We could use a syscon device (which exposes a regmap) for the GPBR
> block.
>
> rtc@ffffff20 {

rtt

> compatible = "atmel,at91sam9260-rtt";
> reg = <0xfffffd20 0x10>;
> interrupts = <1 4 7>;
> clocks = <&clk32k>;
> atmel,time-reg = <&gpbr 0x0>;
> };
>
> gpbr: syscon@fffffd50 {
> compatible = "atmel,at91sam9260-gpbr", "syscon";
> reg = <0xfffffd50 0x10>;
>
> };

Yes, this essentially what I suggested in the thread (and my last reply)
and relying on syscon rather than a custom driver seems like a good
idea. It would allow early access to the registers too with the recently
proposed changes. It would not guarantee any kind of exclusivity,
though, but I guess that's tolerable?

Johan