On 28/01/14 15:18, [email protected] wrote:
> I have what I think is a working DTS as the UART is working fine but I cannot
> get the system to read the PPS from a GPS unit I have connected.
>
> Below is my DTS and the UART 4 is working fine and I have the GPS's PPS
> connected to P8-26 and so I'm hoping my DTS puts it into Mode7 on that pin.
>
> PPS support is inside my kernel
>
> Any ideas at all?
I haven't specifically tried PPS through devicetree yet, however..
gps_pps_pins: pinmux_gps_pps_pins {
pinctrl-single,pins = <0x7c 0x27 /* P8.26 gpio1_29 */
> >;
and
pps {
compatible = "pps-gpio";
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&gps_pps_pins>;
gpios = <&gpio2 7 0 >;
assert-rising-edge;
};
are using two different gpio pins. You're setting the pinmux for gpio1_29 then
telling pps-gpio to use gpio2_7
Also you should be aware that this will depend on which kernel version you're
using.
Some kernels have the &gpio2 reference off-by-one which means that:
0x7c 0x27 /* P8.26 gpio1_29 */ would be referred to as &gpio2 29 as someone
ignored the docs which use gpio0,gpio1,gpio2,gpio3 and called them 1-4 instead..
That's fixed in other kernels, but it does mean that your overlay needs to be
different for each kernel. Similar off-by-one problems exist elsewhere in the
BBB dts, so it's sometimes wise to use dtc to decompile the main dtb and
backtrace the references to see if it's really referring to what you think it
is!
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