GPIO configuration on device Tree[Beagle Board]

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1

Hi. I am using Robert C. Nelson’s kernel on my Beagle Board Rev-C

I want to use mmc2 ports as GPIO.

There is 8 pins in mmc and the default configuration in device tree is =

mmc2: mmc@480b4000 {
compatible = “ti,omap3-hsmmc”;
reg = <0x480b4000 0x200>;
interrupts = <86>;
ti,hwmods = “mmc2”;
dmas = <&sdma 47>, <&sdma 48>;
dma-names = “tx”, “rx”;
};

but disbled default in omap3-beagle.dts. So how should i use these ports as GPIO(not as mmc2) and pull them HIGH and direction > out during sturtup?

I am a newbie, I’ve tried many things but still can’t solve.

Any help could be great.

Thanks.

2

Hi. I am using Robert C. Nelson's kernel on my Beagle Board Rev-C

I want to use mmc2 ports as GPIO.

There is 8 pins in mmc and the default configuration in device tree is =

mmc2: mmc@480b4000 {
compatible = "ti,omap3-hsmmc";
reg = <0x480b4000 0x200>;
interrupts = <86>;
ti,hwmods = "mmc2";
dmas = <&sdma 47>, <&sdma 48>;
dma-names = "tx", "rx";
};

but disbled default in omap3-beagle.dts. So how should i use these ports as
GPIO(not as mmc2) and pull them HIGH and direction > out during sturtup?

I am a newbie, I've tried many things but still can't solve.

See this example of the "eMMC" reset gpio on the black, pick the
correct gpio on the xm and it'll work the same..

Step 1: define the pins a pinmux..

mmc1_pins: pinmux_mmc1_pins {
     pinctrl-single,pins = <
          0x160 (PIN_INPUT | MUX_MODE7) /* GPIO0_6 */
     >;
};

Step 2: gpio-hog...

&gpio1 {
     emmc_rst {
          gpio-hog;
          gpios = <20 0>;
          output-high;
          line-name = "EMMC ResetN";
     };
};

Regards,

3

re-adding the beagle list...

Thanks for your help. But it is getting complicated. :S

Ok. Lets keep it simple. Assume that i just want to light on a led from
MMC2_DAT7 whis is equal to GPIO_139 in Beagleboard.

I test GPIO's by exporting under /sys/class/gpio and echo > high to
direction. Works well under kernel ver. 3.0.x with Angstrom distro. My leds
are on.

Ok here is the story:

I am using your directions under eewiki with kernel 4.x + ubuntu.

1) First i tried to handle this from u-boot, so i pulled every MMC2_DAT* to
MUX_4 (Which is assigned to GPIO's for documentation) . Reboot again with
new u-boot image from SD. Nothing was happened. So i tought Kernel is
blocking GPIO behave of this ports.

Question 1: Does patching only u-boot is enough or necessary? Did i
missing something?

2) Then i start to investigate Kernel Device Tree file from
https://github.com/RobertCNelson/dtb-rebuilder/tree/4.1-ti/src/arm.

I found some documentation under dtb-rebuilder/Bindings/gpio/ . gpio.txt and
gpio-omap.txt. Read them.

Then I found that omap3-beagle.dts and omap3.dtsi are main files. And in
these files:

mmc2: mmc@480b4000 {
compatible = "ti,omap3-hsmmc";
reg = <0x480b4000 0x200>;
interrupts = <86>;
ti,hwmods = "mmc2";
dmas = <&sdma 47>, <&sdma 48>;
dma-names = "tx", "rx";
};

&mmc2 {
status = "disabled";
};

Acoording to this files i understand that mmc2 pins are handled by kernel
and disabled default. Next i deleted this files rebooted and tested again
still nothing was happened.

Leave the mmc2 disabled section..

Question 2: Why kernel still blocks this ports to behave like GPIO even i
remove them in device tree and applied mux_4 in u-boot?

3) Then i removed mmc comments and asked this question here. Now i tried
the example that you gave as:

&mmc2 {
status = "disabled";
};

still remains and i added:

&omap3_pmx_core {
    .....
mmc2_pins: pinmux_mmc2_pins {
pinctrl-single,pins = <
0x016A (PIN_INPUT | MUX_MODE4) /* GPIO_139 -pin3 -mmc_dat_7 */
>;
};

}

And this part gives Error while "make":

&gpio139{
     GPIO_139 {
          gpio-hog;
          gpios = <20 0>;
          output-high;
          line-name = "GPIO_139";
     };
};

//'gpio139', not found at this line &gpio139{

options are &gpio1 -> &gpio6, pick the correct "bank" that gpio139 is in..

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/omap3.dtsi#n216

Then i removed and make again. Builded but stil nothing happens

Question 3: Must i remove mmc2 status="disabled" part?

Question 4: Where and how should i define &gpio139 or must i leave it as
&gpio1

Question 5: Is first part enough to test GPIO from /sys/class/gpio/ or must
i add tthe second part too? line-name = "GPIO_139"; What is it related with?

Question 6: Is 0x016A the offset of the register? According to what? Where
can i find the documentation of these adresses or offsets? In u-boot's
mux.h they differs.

This offset can be found in the dm3730 reference manual.

For example in omap3-beagle.dts > 0x0ac (PIN_OUTPUT | MUX_MODE0) /*
dss_data0.dss_data0 */

But in u-boot -> mux.h #define CONTROL_PADCONF_DSS_DATA0
0x00DC

I confused in there.

If you have time and if you may answer them it should be greaceful.

Regards,

4

Sorry i answered last message directly to you.

Now i rearranged the omap3-beagle.dts.

sudo cat /sys/kernel/debug/gpio >

…
GPIOs 128-159, platform/49058000.gpio, gpio:
…

So i picked up &gpio6 for GPIO_139 and set gpios = <11 0>;

I’ve searched in dm3730 reference manual but there is no knowledge about offsets of registers.

But i found offset 0x16A in http://elinux.org/BeagleBoardPinMux#Pin_Mux_Cross_Reference_Table

I’ve also found real physical adress of the register CONTROL_PADCONF_MMC2_DAT6[31:16] ==== 0x4800 2168 ==== mmc2_dat7 in OMAP35 Techinical Reference Manual.

So i combined them and

&omap3_pmx_core {
…
…
…
mmc2_pins: pinmux_mmc2_pins {
pinctrl-single,pins = <
0x16A (PIN_OUTPUT | MUX_MODE4)

;
};
};
&gpio6{
GPIO_139 {
gpio-hog;
gpios = <11 0>;
output-high;
line-name = “GPIO_139_6”;
};
};

make & make install & reboot.

But still nothing happens. My LED still remains silently.

when i checked sudo cat /sys/kernel/debug/gpio

GPIOs 128-159, platform/49058000.gpio, gpio:
gpio-138 (tfp410 PD ) out hi
gpio-139 (GPIO_139_6 ) out hi

it looks ok. And also

dmesg | grep GPIO

[ 0.811126] GPIO line 139 (GPIO_139_6) hogged as output/high

what am i doing wrong? I suspect about pin offset but dont enough knowledge of this is offset of what and how to calculate. So i cannot be sure what is wrong.

Best Wishes.