Linux/PROCESSOR-SDK-OMAPL138: Unable to toggle GPIO LED's in Linux

Dmitriy Stepin

Part Number: PROCESSOR-SDK-OMAPL138
Other Parts Discussed in Thread: OMAP-L138

Tool/software: Linux

Hi,

I want to be able to toggle and set GPIO's on the OMAP-L138 LCDK via Linux. I am running the latest Linux out of the Processor SDK provided.

I have followed the instructions provided in this thread:

and here:

I have modified my arch/arm/mach-davinci/include/mach/mux.h to include

DA850_GPIO0_9,
DA850_GPIO2_12,
DA850_GPIO6_12,

I have modified arch/arm/mach-davinci/da850.c to include for PINMUX

MUX_CFG(DA850, GPIO0_9,		0,	24,	15,	8,	false)
MUX_CFG(DA850, GPIO2_12,	5,	12,	15,	8,	false)
MUX_CFG(DA850, GPIO6_12,	13,	12,	15,	8,	false)

and I have also modified both arch/arm/mach-davinci/board-omapl138-hawk.c and arch/arm/mach-davinci/board-da850-evm.c to include

	/* Configure the LED Pins D7, D6, D5, D4 for LCDK */
	ret = davinci_cfg_reg(DA850_GPIO0_9);
	if (ret)
		pr_warn("%s:GPIO(0,9) mux setup failed\n", __func__);

	ret = davinci_cfg_reg(DA850_GPIO2_12);
	if (ret)
		pr_warn("%s:GPIO(2,12) mux setup failed\n", __func__);

	ret = davinci_cfg_reg(DA850_GPIO6_12);
	if (ret)
		pr_warn("%s:GPIO(6,12) mux setup failed\n", __func__);

	ret = davinci_cfg_reg(DA850_GPIO6_13);
	if (ret)
		pr_warn("%s:GPIO(6,13) mux setup failed\n", __func__);

However, when I access /sys/class/gpio and export the GPIO's I can't edit their values, they never change.

I am able to change their directions, however i cannot set the values.

I set echo 'out' > direction and it goes through, then when I do echo 1 > value, the value doesn't change.

/sys/kernel/debug/gpio shows the GPIO's that are exported through the sysfs, their directions can change but not the values.

What am I doing wrong here? Or what can I do to be able to toggle the GPIO's through the Linux system. I assumed I pinmuxed them all correctly.

over 5 years ago

0 Cvetolin Shulev-XID over 5 years ago

TI__Guru 65405 points

Hi Dmitriy,

The team is notified. They will post their feedback directly here.

BR
Tsvetolin Shulev

0 Yordan Kovachev over 5 years ago

TI__Guru**** 161600 points

Hi,

Which Processor SDK Linux version is this?

Best Regards,
Yordan

0 Dmitriy Stepin over 5 years ago in reply to Yordan Kovachev

Intellectual 585 points

It's 04.03.00.05

0 Yordan Kovachev over 5 years ago in reply to Dmitriy Stepin

TI__Guru**** 161600 points

Hi Dmitry,

I this sdk the board files in mach-davinci folder are not used.
Pinmux is performed in arch/arm/boot/dts/da850.dtsi -> pmx_core: pinmux@14120 {
and in arch/arm/boot/dts/da850-lcdk.dts -> &pmx_core {

You should add the gpio pinmux there. Then later in da850-lcdk.dts you should add:
&gpio0 {
pinctrl-names = "default";
pinctrl-0 = <&gpio0_pins>;
status = "okay";
} ;
&gpio2 {
pinctrl-names = "default";
pinctrl-0 = <&gpio2_pins>;
status = "okay";
};
&gpio6 {
pinctrl-names = "default";
pinctrl-0 = <&gpio6_pins>;
status = "okay";
};

Of course you should also check that there are NO pinmux conflicts (make sure there isn't any other dts node or driver that uses these gpio pins).

Best Regards,
Yordan

0 Dmitriy Stepin over 5 years ago in reply to Yordan Kovachev

Intellectual 585 points

Hey,

So I receive the following error when building my linux kernel:

Error: arch/arm/boot/dts/da850-lcdk.dts:199.1-7 Label or path gpio0 not found
Error: arch/arm/boot/dts/da850-lcdk.dts:205.1-7 Label or path gpio2 not found
Error: arch/arm/boot/dts/da850-lcdk.dts:211.1-7 Label or path gpio6 not found
FATAL ERROR: Syntax error parsing input tree
scripts/Makefile.lib:313: recipe for target 'arch/arm/boot/dts/da850-lcdk.dtb' failed
make[2]: *** [arch/arm/boot/dts/da850-lcdk.dtb] Error 1
arch/arm/Makefile:336: recipe for target 'da850-lcdk.dtb' failed
make[1]: *** [da850-lcdk.dtb] Error 2
make[1]: *** Waiting for unfinished jobs....
make[1]: Leaving directory '/home/dmitriy/ti-processor-sdk-linux-omapl138-lcdk-04.03.00.05/board-support/linux-4.9.69+gitAUTOINC+9ce43c71ae-g9ce43c71ae'
Makefile:313: recipe for target 'linux-dtbs' failed
make: *** [linux-dtbs] Error 2

I have made those modifications the da850-lcdk.dts

To &pmx_core I added:

	gpio0_pins: pinmux_gpio0_pins {
		pinctrl-single,bits = <
			/* GP0[9] */
			0x00 0x08000000  0x0f000000
		>;
	};

	gpio2_pins: pinmux_gpio2_pins {
		pinctrl-single,bits = <
			/* GP2[12] */
			0x14 0x00008000  0x0000f000
		>;
	};

	gpio6_pins: pinmux_gpio6_pins {
		pinctrl-single,bits = <
			/* GP6[12], GP6[13] */
			0x34 0x00008800  0x0000ff00
		>;
	};

I also added in just the DTS:

&gpio0 {
	pinctrl-names = "default";
	pinctrl-0 = <&gpio0_pins>;
	status = "okay";
};

&gpio2 {
	pinctrl-names = "default";
	pinctrl-0 = <&gpio2_pins>;
	status = "okay";
};

&gpio6 {
	pinctrl-names = "default";
	pinctrl-0 = <&gpio6_pins>;
	status = "okay";
};

I'm guessing it's because I haven't added those labels to the da850.dtsi

The only gpio label in there is this one:

		gpio: gpio@226000 {
			compatible = "ti,dm6441-gpio";
			gpio-controller;
			#gpio-cells = <2>;
			reg = <0x226000 0x1000>;
			interrupts = <42 IRQ_TYPE_EDGE_BOTH
				43 IRQ_TYPE_EDGE_BOTH 44 IRQ_TYPE_EDGE_BOTH
				45 IRQ_TYPE_EDGE_BOTH 46 IRQ_TYPE_EDGE_BOTH
				47 IRQ_TYPE_EDGE_BOTH 48 IRQ_TYPE_EDGE_BOTH
				49 IRQ_TYPE_EDGE_BOTH 50 IRQ_TYPE_EDGE_BOTH>;
			ti,ngpio = <144>;
			ti,davinci-gpio-unbanked = <0>;
			status = "disabled";
		};

I'm not sure how I would extend the da850.dtsi with the gpio0, gpio2, and gpio6 labels.

0 Yordan Kovachev over 5 years ago in reply to Dmitriy Stepin

TI__Guru**** 161600 points

Hi,

Sorry for the delay. This is my bad. You're getting this error because in da850.dtsi the gpio is defined as:
gpio: gpio@226000

And then in da850-lcdk.dts it is enabled like:
&gpio {
status = "okay";
};

So you just need to figure out the pin number you want to use, pinmux it and make sure it is NOT used in any other dts node.

Best Regards,
Yordan

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Linux/PROCESSOR-SDK-OMAPL138: Unable to toggle GPIO LED's in Linux