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

Johan Hovold
2014-09-10T12:16:25Z

On Wed, Sep 03, 2014 at 10:45:34AM +0200, Boris BREZILLON wrote:
> Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
> ---
> .../devicetree/bindings/rtc/atmel,at91sam9-rtc.txt | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/rtc/atmel,at91sam9-rtc.txt
>
> diff --git a/Documentation/devicetree/bindings/rtc/atmel,at91sam9-rtc.txt b/Documentation/devicetree/bindings/rtc/atmel,at91sam9-rtc.txt
> new file mode 100644
> index 0000000..9ca455f
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/rtc/atmel,at91sam9-rtc.txt
> @@ -0,0 +1,20 @@
> +Atmel AT91SAM9260 Real Time Timer
> +
> +Required properties:
> +- compatible: should be: "atmel,at91sam9260-rtt"
> +- reg: should contain 2 memory regions
> + * the first one encodes the memory region of the RTT controller
> + * the second one encodes the GPBR (General Purpose Backup Resgisters)
> + memory region used to store the current time
> +- interrupts: rtc alarm/event interrupt
> +- clocks: should contain one clock pointing the the slow clk
> +
> +Example:
> +
> +rtc@fffffe00 {
> + compatible = "atmel,at91sam9260-rtt";
> + reg = <0xfffffd20 0x10
> + 0xfffffd50 0x4>;
> + interrupts = <1 4 7>;
> + clocks = <&clk32k>;
> +};

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).

This was discussed in the thread where I posted an RFC for this last
year (which you linked to in your original submission thread), but no
conclusion was reached:

http://www.spinics.net/lists/arm-kernel/msg236292.html

Johan