PIN_MUX P9_26 not

dzhou · September 16, 2020, 1:48pm

Hi Robert,
(kernel version: 4.19.50-ti-r20)
When I try to
config-pin P9.24 can and config-pin P9.26 can
I got the following error:
ERROR: open() for /sys/devices/platform/ocp/ocp:P9_24_pinmux/state failed
ERROR: open() for /sys/devices/platform/ocp/ocp:P9_26_pinmux/state failed

I found that the pinmux for both are not listed under :
/sys/devices/platform/ocp

The above is booted with CAPE on. But without CAPE, both pinmux are there.
Is CAPE Overlay not loaded or is CAPE Overlay conflicting with something else.?
What the best way to resolve it?

(CAN1 is working under Stretch)

Thank you,
David

RobertCNelson · September 16, 2020, 1:57pm

Hi @dzhou ,

When an overlay takes a pin for a specific function, the overlay disables the corresponding config-pin entry.

Regards,

dzhou · September 16, 2020, 2:01pm

Hi Robert,

Can you please help with some suggestions how to resolve the issue? It is new to me with these overlays.

Thank you,
David

RobertCNelson · September 16, 2020, 4:44pm

Hi @dzhou, sorry i’m confused, does CAN1 work out of the box with out touching config-pin?

config-pin is used to quickly change the pinmux of pin’s on the fly. However when you load a device specific overlay, that ability is removed, as the overlay has a specific pinmux for the device, such that i’ll just work.

So, out of box with that BeagleBone Cape, the CAN1 bus should be muxed and working, if not we have another issue to deal with…

Regards,

dzhou · September 16, 2020, 4:48pm

Hi Robert,
CAN1 works on BBBw with CAPE, and BBBw loaded with Stretch version.
It needs to config-pins, too.

Now, I couldn’t be sure. But I believe it needs config-pins.

Regards,
David

RobertCNelson · September 16, 2020, 4:58pm

These two lines disable config-pin for those pins:

github.com

beagleboard/bb.org-overlays/blob/master/src/arm/BB-CAN1-00A0.dts#L52-L53


			P9_24_pinmux { status = "disabled"; };	/* P9_24: uart1_txd.d_can1_rx */
			P9_26_pinmux { status = "disabled"; };	/* P9_26: uart1_rxd.d_can1_tx */

The final pinmux setting are set here:

github.com

beagleboard/bb.org-overlays/blob/master/src/arm/BB-CAN1-00A0.dts#L57-L77


	fragment@2 {
		target = <&am33xx_pinmux>;
		__overlay__ {
			bb_dcan1_pins: pinmux_dcan1_pins {
				pinctrl-single,pins = <
					BONE_P9_24 (PIN_INPUT_PULLUP | MUX_MODE2)	/* P9_24: uart1_txd.d_can1_rx */
					BONE_P9_26 (PIN_OUTPUT_PULLUP | MUX_MODE2)	/* P9_26: uart1_rxd.d_can1_tx */
				>;
			};
		};
	};

	fragment@3 {
		target = <&dcan1>;
		__overlay__ {
			status = "okay";
			pinctrl-names = "default";
			pinctrl-0 = <&bb_dcan1_pins>;
		};
	};
};

Thus config-pin is not used…

Regards,

dzhou · September 16, 2020, 6:12pm

Hi Robert,

We got CAN working. Buster (2019-07 version) is just fine without recompiling overlays. Just config pins. We have our end problem, the mode control is implemented on our board. After grounding the pin, it just worked.

Thank you for your help,
David