AM6442: How gpiochip pin numbers are mapped to schematic?

Jakub Grad

Part Number: AM6442

Hello

I want to light up the LED connected to the RPI_GPIO0_42 Expansion connector pin using /dev/gpiochip3. How pin numbers listed with the command: gpioinfo 3 map to the pins of the AM6442 processor? On the schematic (https://www.ti.com/lit/pdf/sprr432) the pin RPI_GPIO0_42 is pin R20.

root@am64xx-evm:/sys/class/gpio/gpiochip327# gpioinfo 3
gpiochip3 - 88 lines:
        line   0:      unnamed       unused   input  active-high
        line   1:      unnamed       unused   input  active-high
        line   2:      unnamed       unused   input  active-high
        line   3:      unnamed       unused   input  active-high
        line   4:      unnamed       unused   input  active-high
        line   5:      unnamed       unused   input  active-high
        line   6:      unnamed       unused   input  active-high
        line   7:      unnamed       unused   input  active-high
        line   8:      unnamed       unused   input  active-high
        line   9:      unnamed       unused   input  active-high
        line  10:      unnamed       unused   input  active-high
        line  11:      unnamed       unused   input  active-high
        line  12:      unnamed       unused   input  active-high
        line  13:      unnamed       unused   input  active-high
        line  14:      unnamed       unused   input  active-high
        line  15:      unnamed       unused   input  active-high
        line  16:      unnamed       unused   input  active-high
        line  17:      unnamed       unused   input  active-high
        line  18:      unnamed       unused   input  active-high
        line  19:      unnamed       unused   input  active-high
        line  20:      unnamed       unused   input  active-high
        line  21:      unnamed       unused   input  active-high
        line  22:      unnamed       unused   input  active-high
        line  23:      unnamed       unused   input  active-high
        line  24:      unnamed       unused   input  active-high
        line  25:      unnamed       unused   input  active-high
        line  26:      unnamed       unused   input  active-high
        line  27:      unnamed       unused   input  active-high
        line  28:      unnamed       unused   input  active-high
        line  29:      unnamed       unused   input  active-high
        line  30:      unnamed       unused   input  active-high
        line  31:      unnamed       unused   input  active-high
        line  32:      unnamed       unused   input  active-high
        line  33:      unnamed       unused   input  active-high
        line  34:      unnamed       unused   input  active-high
        line  35:      unnamed       unused   input  active-high
        line  36:      unnamed       unused   input  active-high
        line  37:      unnamed       unused   input  active-high
        line  38:      unnamed       unused   input  active-high
        line  39:      unnamed       unused   input  active-high
        line  40:      unnamed       unused   input  active-high
        line  41:      unnamed       unused   input  active-high
        line  42:      unnamed       unused   input  active-high
        line  43:      unnamed       unused   input  active-high
        line  44:      unnamed       unused   input  active-high
        line  45:      unnamed       unused   input  active-high
        line  46:      unnamed       unused   input  active-high
        line  47:      unnamed       unused   input  active-high
        line  48:      unnamed       unused   input  active-high
        line  49:      unnamed       unused   input  active-high
        line  50:      unnamed       unused   input  active-high
        line  51:      unnamed       unused   input  active-high
        line  52:      unnamed       unused   input  active-high
        line  53:      unnamed       unused   input  active-high
        line  54:      unnamed       unused   input  active-high
        line  55:      unnamed       unused   input  active-high
        line  56:      unnamed       unused   input  active-high
        line  57:      unnamed       unused   input  active-high
        line  58:      unnamed       unused   input  active-high
        line  59:      unnamed       unused   input  active-high
        line  60:      unnamed       unused   input  active-high
        line  61:      unnamed       unused   input  active-high
        line  62:      unnamed       unused   input  active-high
        line  63:      unnamed       unused   input  active-high
        line  64:      unnamed       unused   input  active-high
        line  65:      unnamed       unused   input  active-high
        line  66:      unnamed       unused   input  active-high
        line  67:      unnamed       unused   input  active-high
        line  68:      unnamed       unused   input  active-high
        line  69:      unnamed       unused   input  active-high
        line  70:      unnamed       unused   input  active-high
        line  71:      unnamed       unused   input  active-high
        line  72:      unnamed       unused   input  active-high
        line  73:      unnamed       unused   input  active-high
        line  74:      unnamed       unused   input  active-high
        line  75:      unnamed       unused   input  active-high
        line  76:      unnamed       unused   input  active-high
        line  77:      unnamed       unused   input  active-high
        line  78:      unnamed       unused   input  active-high
        line  79:      unnamed       unused   input  active-high
        line  80:      unnamed       unused   input  active-high
        line  81:      unnamed       unused   input  active-high
        line  82:      unnamed       unused   input  active-high
        line  83:      unnamed       unused   input  active-high
        line  84:      unnamed       unused   input  active-high
        line  85:      unnamed       unused   input  active-high
        line  86:      unnamed       unused   input  active-high
        line  87:      unnamed       unused   input  active-high

Thank you,

Jakub

over 3 years ago

0 Bin Liu over 3 years ago

TI__Guru**** 171861 points

Hi Jakub,

if gpiochip3 is for GPIO0 bank, then line 0 is GPIO0_0, line 1 is GPIO0_1, and so on. So line 42 is GPIO0_42.

0 Jakub Grad over 3 years ago in reply to Bin Liu

Intellectual 730 points

Is there any configuration file that describe this pin relation?

0 Bin Liu over 3 years ago in reply to Jakub Grad

TI__Guru**** 171861 points

line 0 is GPIO0_0, line 1 is GPIO0_1, ...

What configuration do you need for this simple pin mapping?

0 Jakub Grad over 3 years ago in reply to Jakub Grad

Intellectual 730 points

In our custom hardware based on AM53 there will be need to remap some pins. I wondering if it is some kind of configuration file where i can define which pin is which.

0 Bin Liu over 3 years ago in reply to Jakub Grad

TI__Guru**** 171861 points

Do you means something like, for example, line0 is GPIO0_7? You cannot do that. You can customize the pin names though.

0 Jakub Grad over 3 years ago in reply to Bin Liu

Intellectual 730 points

Ok, back to the beginning: on the schematic, pin 42 (with expansion connector) is pin R20. How does the driver know that line 42 is actually CPU pin R20. Is it configurable and where?

0 Jakub Grad over 3 years ago in reply to Jakub Grad

Intellectual 730 points

Ok, I see that this info is in AM64 datasheet. How to set pin high? I used gpiochip 3 42=1 but voltage on pin 42 is still low

0 Bin Liu over 3 years ago in reply to Jakub Grad

TI__Guru**** 171861 points

The GPIO default is in input mode. Did you configure it to output mode?

0 Bin Liu over 3 years ago in reply to Bin Liu

TI__Guru**** 171861 points

And did you configure pin R20 pinmux to GPIO mode?

0 Jakub Grad over 3 years ago in reply to Bin Liu

Intellectual 730 points

After call this command gpiochip 3 42=1 the pin is visible as output.

0 Jakub Grad over 3 years ago in reply to Bin Liu

Intellectual 730 points

Ok, I must check it

0 Jakub Grad over 3 years ago in reply to Jakub Grad

Intellectual 730 points

The following node is defined in the k3-am64-main.dtsi tree. Do I need to add another node to the device tree to be able to use GPIO? Can you share any example of how to write such a node?

main_gpio1: gpio@601000 {
		compatible = "ti,am64-gpio", "ti,keystone-gpio";
		reg = <0x0 0x00601000 0x0 0x100>;
		gpio-controller;
		#gpio-cells = <2>;
		interrupt-parent = <&main_gpio_intr>;
		interrupts = <180>, <181>, <182>,
			     <183>, <184>, <185>;
		interrupt-controller;
		#interrupt-cells = <2>;
		ti,ngpio = <88>;
		ti,davinci-gpio-unbanked = <0>;
		power-domains = <&k3_pds 78 TI_SCI_PD_EXCLUSIVE>;
		clocks = <&k3_clks 78 0>;
		clock-names = "gpio";
	};

0 Jakub Grad over 3 years ago in reply to Bin Liu

Intellectual 730 points

I added device tree overlay, but still doesn't work.

/dts-v1/;
/plugin/;

 #include "dt-bindings/pinctrl/k3.h"
 #include "dt-bindings/gpio/gpio.h"
/ {

        compatible = "ti,am642-sk", "ti,am642";

        fragment@0 {
                target = <&main_pmx0>;
                __overlay__ {
                        gpio_test_hardware_pins: gpio-test-hardware-pins-default {
                                pinctrl-single,pins = <
                                        AM64X_IOPAD(0x00AC, PIN_OUTPUT, 7) /* (R20) GPIO0_42 */
                                >;
                        };
                };

        };
};

0 Bin Liu over 3 years ago in reply to Jakub Grad

TI__Guru**** 171861 points

Jakub Grad said:
I added device tree overlay, but still doesn't work.

Besides adding the pinmux setting, you have to "activate" it. Please see my last post in the following thread:
https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1082477/processor-sdk-am64x-am64-sk-can-not-toggle-gpio-output/4012782#4012782

0 Jakub Grad over 3 years ago in reply to Bin Liu

Intellectual 730 points

Can I add this reference to any custom node? for example:

 fragment@0 {
                target = <&main_pmx0>;
                __overlay__ {
                        gpio_test_hardware_pins: gpio-test-hardware-pins-default {
                                pinctrl-single,pins = <
                                        AM64X_IOPAD(0x00AC, PIN_OUTPUT, 7) /* (R20) GPIO0_42 */
                                >;
                        };
                };

};

fragment@1 {
    target-path = "/"
    __overlay__ {
        xnode : x-node {
             pinctrl-names = "default";
             pinctrl-0 = <&gpio_test_hardware_pins>;  
        };
    };
};

0 Jakub Grad over 3 years ago in reply to Bin Liu

Intellectual 730 points

How to determine which gpiochip to use? For example I have added gpio to pinmux in device tree. For this pin gpiochip 2 is used but why not gpiochip 3?

0 Bin Liu over 3 years ago in reply to Jakub Grad

TI__Guru**** 171861 points

Jakub Grad said:
Can I add this reference to any custom node? for example:

Though it is not a good practice to add it to any node, but technically it would work, as long as the DT node has a kernel driver associated with, so that the DT node will get parsed by the driver and the pinmux will get "activated".

In your example above, you create a new DT node "x-node", you have to ensure it has the "compatible" property defined and kernel will find the driver for this "x-node".

0 Bin Liu over 3 years ago in reply to Jakub Grad

TI__Guru**** 171861 points

Jakub Grad said:
How to determine which gpiochip to use?

You can use command "ls -l /sys/class/gpio/", the output shows the symlink of each gpiochip pointing to the corresponding GPIO hardware module.

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AM6442: How gpiochip pin numbers are mapped to schematic?