How to get pin to mode 6 on beagle bone black

[Hans Bentum]

Hello,

I tried several things to put pin 8_16 into mode 6 for usage by the PRU for
high speed IO.
Up to now without any luck.  I am using FreeBSD 12.1

Question: how can I put a pin on beagle bone black to mode 6?

I did the following:

To get full speed IO signals I would like to use the enhanced GPIO on the
PRU.
To do this a device tree overlay is needed. I found a nice example on the
internet. https://nilshoel.home.blog/
In this example pin P8.16 is set to input mode 6.

/dts-v1/;
/plugin/;

/ {
compatible = "ti,beaglebone", "ti,beaglebone-black", "ti,beaglebone-green";

    // identification
    part-number = "PRU-UIO-EXAMPLE-PINS";
    version = "00A0";


   fragment at 0 {
    target = <&am33xx_pinmux>;
    __overlay__ {
      example_pins: pinmux_pru_pru_pins {
       pinctrl-single,pins = <
         0x38 0x26 /* Pin 8_16 in gpmc_ad14 Mode 6 */
       >;
      };
    };
   };


   fragment at 1 {
    target-path="<&pruss>";
    __overlay__ {
      pinctrl-names = "default";
      pinctrl-0 = <&example_pins>;
      status = "okay";
     };
   };
};


The file (egpio.dtso) is converted by

dtc –I dts –O dtb –o /boot/dtb/overlays/egpio.dtbo egpio.dtso

The egpio.dtbo is added in the file loader.conf to the line

fdt_overlays="am335x-boneblack-pruss.dtbo,egpio.dtbo"

am335x-boneblack-pruss.dtbo is to enable the pruss

/dts-v1/;
/plugin/;

/ {
                compatible = "ti,am335x-bone-black", "ti,am335x-bone",
"ti,am33xx";

                fragment at 0 {
                               target-path="/";
                               __overlay__ {
                                               ocp {

#address-cells = <1>;
                                                               #size-cells
= <1>;


pruss at 4a300000 {

status = "okay";

compatible = "ti,pruss-v2";

ti,deassert-hard-reset = "pruss", "pruss";

reg = <0x4a300000 0x080000>;

ti,pintc-offset = <0x20000>;

interrupt-parent = <&intc>;

interrupts = <20 21 22 23 24 25 26 27>;
                                                               };
                                               };
                               };
                };
};

In the PRU(0) I start a little test program which sets a userled
to on when the pin is sampled high and sets the userled to off when the pin
is sampled low.
The pin should be in mode 6 to be able to read the high value. If I use
some timer construction in the pru assembly  program bellow the leds are
blinking so the pru is up and running.

# cat rtu_w.p

.origin 0
.entrypoint START

#define GPIO0              0x44E07000
#define GPIO1              0x4804c000
#define GPIO2              0x481AC000
#define GPIO3              0x481AE000

#define GPIO_CLEARDATAOUT       0x190
#define GPIO_SETDATAOUT         0x194

#define LED_USER   1<<24
#define CONST_PRUCFG            C4
#define CTPPR_0         0x24028
#define CTPPR_1         0x2402C

.macro ST32
.mparam src,dst
    SBBO    src,dst,#0x00,4
.endm

START:LBCO    r0, CONST_PRUCFG, 4, 4
      CLR     r0, r0,
      SBCO    r0, CONST_PRUCFG, 4, 4

      MOV     r0, 0x00000100
      MOV     r1, CTPPR_0
      ST32    r0, r1

      MOV     r0, 0x00100000
      MOV     r1, CTPPR_1
      ST32    r0, r1

NO_CMD:QBBC L1, r31.t14                                             //
Quick Branch to L1 if Bit is Clear
       CALL LED_USER_LANE_1_ON
       QBA NO_CMD
L1:    CALL LED_USER_LANE_1_OFF
       QBA NO_CMD

LED_USER_LANE_1_ON: MOV r2, LED_USER
                    MOV r3, GPIO1 | GPIO_SETDATAOUT
                    SBBO r2, r3, 0, 4
                    RET

LED_USER_LANE_1_OFF:            MOV r2, LED_USER
      MOV r3, GPIO1 | GPIO_CLEARDATAOUT
                                                               SBBO r2, r3,
0, 4
                                                               RET


Makefile

pru = rtu_w

LIB_PATH = .
LIBRARIES = pthread

INCLUDES = -I. ${LIB_PATH}
INCLUDES = -I/home/freebsd/iws


EXTRA_DEFINE =
CCCFLAGS = $(EXTRA_DEFINE)
CC = clang
CFLAGS = $(EXTRA_DEFINE)
PASM = pasm

all : $(clean) $(pru)
pru : $(pru)

$(pru) : $(pru:%=%.p)
        rm -rf *.o *.bin $(project) core *~
        $(PASM) -V3 -b $@.p

clean:
      rm -rf *.o *.bin $(project) core *~

compile wtih:
#make

Run on pru:(and give the pin signals)
# pructl –t ti –p 0 –e rtu_w.bin

I also tried to set the pinmux using the pru but no luck (as expected).
https://vadl.github.io/beagleboneblack/2016/07/29/setting-up-bbb-gpio

#define P8_16                                 0x44E10838
          MOV     r2, 0x26                     // val
          MOV     r0, P8_16                  // address
          SBBO    r2, r0, 0, 4                  // store


For low speed setting or reading pin like

#include <libgpio.h>

  gself.m_gpio2 = gpio_open(2);
  gpio_pin_input (gself.m_gpio2, 22);
  gpio_close(gself.m_gpio2);

works very well.

 Regards,
Hans Bentum