On 9/4/24 23:19, Rob Herring wrote:
On Wed, Sep 4, 2024 at 12:09 PM Ayush Singh <ayush@xxxxxxxxxxxxxxx> wrote:
gpio-map is what you are looking for. It's documented in the DT spec.
It was created exactly for this purpose of remapping GPIO lines on a
connector.
Rob
Hi. I found docs on nexus nodes [1] and tried using it for mikroBUS, but
it does not seem to be working. Here is my connector:
```
mikrobus_gpio0: mikrobus-gpio0 {
#gpio-cells = <2>;
gpio-map =
<0 0 &main_gpio1 11 0>, <1 0 &main_gpio1 9 0>,
<2 0 &main_gpio1 24 0>, <3 0 &main_gpio1 25 0>,
<4 0 &main_gpio1 22 0>, <5 0 &main_gpio1 23 0>,
<6 0 &main_gpio1 7 0>, <7 0 &main_gpio1 8 0>,
<8 0 &main_gpio1 14 0>, <9 0 &main_gpio1 13 0>,
<10 0 &main_gpio1 12 0>, <11 0 &main_gpio1 10 0>;
gpio-map-mask = <0xf 0x0>;
gpio-map-pass-thru = <0x0 0x1>;
};
...
&main_uart5 {
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&mikrobus_uart_pins_default>;
gnss {
compatible = "u-blox,neo-8";
reset-gpios = <&mikrobus_gpio0 10 GPIO_ACTIVE_LOW>;
};
};
```
After some fdtdump, I can see that at least the dtc compiler does not
seem to do the forwarding at dt compile time. Here is the dump:
dtc knows nothing about it.
```
mikrobus-gpio0 {
#gpio-cells = <0x00000002>;
gpio-map = <0x00000000 0x00000000 0x00000025 0x0000000b
0x00000000 0x00000001 0x00000000 0x00000025 0x00000009 0x00000000
0x00000002 0x00000000 0x00000025 0x00000018 0x00000000 0x00000003
0x00000000 0x00000025 0x00000019 0x00000000 0x00000004 0x00000000
0x00000025 0x00000016 0x00000000 0x00000005 0x00000000 0x00000025
0x00000017 0x00000000 0x00000006 0x00000000 0x00000025 0x00000007
0x00000000 0x00000007 0x00000000 0x00000025 0x00000008 0x00000000
0x00000008 0x00000000 0x00000025 0x0000000e 0x00000000 0x00000009
0x00000000 0x00000025 0x0000000d 0x00000000 0x0000000a 0x00000000
0x00000025 0x0000000c 0x00000000 0x0000000b 0x00000000 0x00000025
0x0000000a 0x00000000>;
gpio-map-mask = <0x0000000f 0x00000000>;
gpio-map-pass-thru = <0x00000000 0x00000001>;
phandle = <0x0000000e>;
};
You might need "gpio-controller" here. Though if you do, I think
that's a mistake in the kernel. It should work like interrupt-map and
generally you have either interrupt-controller or interrupt-map, but
not both (though that is allowed now too).
...
serial@2850000 {
compatible = "ti,am64-uart", "ti,am654-uart";
reg = <0x00000000 0x02850000 0x00000000 0x00000100>;
interrupts = <0x00000000 0x000000b7 0x00000004>;
power-domains = <0x00000003 0x0000009c 0x00000001>;
clocks = <0x00000002 0x0000009c 0x00000000>;
clock-names = "fclk";
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <0x0000000d>;
phandle = <0x00000081>;
gnss {
compatible = "u-blox,neo-8";
reset-gpios = <0x0000000e 0x0000000a 0x00000001>;
};
};
```
So I am a bit unsure. Is the dtc parser in the kernel supposed to do the
No such thing as "dtc parser in the kernel".
mapping, or is it supposed to be done by `dtc` at compile time?
No.
Maybe we
do not have support for it in upstream kernel yet?
Yes, there is upstream support. Grep for of_parse_phandle_with_args_map.
Rob
So, after a bit of troubleshooting, it seems that a nexus node should
not be present at root level (unless it also has an actual driver). If
the nexus node is a root node without an actual driver, anything
referring to the node is deferred.
I am still a bit unsure if I should make the `mikrobus-connector` itself
a nexus node or if I should have a subnode named `mikrobus_gpio`, but at
least things seem to be working now. So, thanks for your help.
Ayush Singh
