Customizing the device tree - Revision history

KrzysztofChojnowski at 10:48, 30 June 2021

2021-06-30T10:48:37Z

← Older revision		Revision as of 10:48, 30 June 2021
Line 153:		Line 153:
	* visioncb-6ull-std-sd.dtb		* visioncb-6ull-std-sd.dtb

	~~Two of them - with or without the wireless modem support - may~~ be copied to the ~~''/boot'' directory~~ of the ~~VisionSOM module storage memory overwriting the existing ones (''~~visionsom-6ull.dtb~~'' and ''~~visionsom-6ull-emmc.dtb~~'').~~		== Installing new device tree files ==
			The new device tree file should be copied to the target system and by replacing existing one. In case of SoMLabs Debian the recognized names are:

			* visionsom-6ull.dtb - for SD card module
			* visionsom-6ull-emmc.dtb - for eMMC module

			The original files are located on the boot partition that should be mounted by using the following command:

			<pre>
			mount /dev/mmcblk1p1 /boot
			</pre>

	'''NOTE!''' It is strongly recommended to check startup messages after loading the device tree. If one of I/O lines is requested by more than one driver then you will get message like the one below:		'''NOTE!''' It is strongly recommended to check startup messages after loading the device tree. If one of I/O lines is requested by more than one driver then you will get message like the one below:

KrzysztofChojnowski at 12:52, 21 August 2020

2020-08-21T12:52:02Z

← Older revision		Revision as of 12:52, 21 August 2020
Line 2:		Line 2:
	Linux version 3.5.7 and newer include a new feature - device trees, they represent connections and structure of the machine it is run on. Modules used in earlier kernels are replaced with Device Tree Blobs (DTB).		Linux version 3.5.7 and newer include a new feature - device trees, they represent connections and structure of the machine it is run on. Modules used in earlier kernels are replaced with Device Tree Blobs (DTB).

	The device tree for VisionSOM-6ULL module is located in the ~~file~~: ~~somlabs~~-visionsom-6ull.~~dts (somlabs~~-visionsom-~~6ul~~.~~dts for VisionSOM~~-~~6UL)~~ located within the Linux kernel source (arch/arm/boot/dts). ~~This file~~ should be edited in order to configure the hardware. Obtaining and building the Linux kernel is described in the [[Customizing the Linux kernel]] article.		The device tree for VisionSOM-6ULL module is located in the following files that are included based on the board configuration:
			* visioncb-6ull-std.dtsi
			* visioncb-6ull-std-emmc-btwifi.dts
			* visioncb-6ull-std-emmc.dts
			* visioncb-6ull-std-sd-btwifi.dts
			* visioncb-6ull-std-sd.dts
			* visionsom-6ull-btwifi.dtsi
			* visionsom-6ull.dtsi
			* visionsom-6ull-emmc.dtsi
			* visionsom-6ull-sd.dtsi

			They are located within the Linux kernel source (arch/arm/boot/dts). The files should be edited in order to configure the hardware. Obtaining and building the Linux kernel is described in the [[Customizing the Linux kernel]] article.

	== GPIO pins definitions ==		== GPIO pins definitions ==
Line 40:		Line 51:
	These pins are connected to the IO8 and IO9 buttons on the VisionCB-STB board.		These pins are connected to the IO8 and IO9 buttons on the VisionCB-STB board.

	Both pins need to be configured in the device tree file. In this example a new section of the ''~~imx6ul~~-~~evk~~'' entry is created:		Both pins need to be configured in the device tree file. In this example a new section of the ''visioncb-6ull'' entry in the ''visioncb-6ull-std.dtsi'' file is created:

	<pre>pinctrl_gpio_in: gpioingrp {		<pre>pinctrl_gpio_in: gpioingrp {
Line 52:		Line 63:
	<pre>&iomuxc {		<pre>&iomuxc {
	pinctrl-names = "default";		pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_hog_1 &pinctrl_gpio_in>;</pre>		pinctrl-0 = <&pinctrl_hog_1 &pinctrl_gpio_in>;
			</pre>

	Now, both inputs may be used by exporting the pins:		Now, both inputs may be used by exporting the pins:
Line 87:		Line 99:
	pinctrl-names = "default";		pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_hog_1>;		pinctrl-0 = <&pinctrl_hog_1>;
	~~imx6ul~~-~~evk~~ {		visioncb-6ull {

	...		...
Line 109:		Line 121:
	UART4 RX (77 pin of the VisionSOM-6ULx module)		UART4 RX (77 pin of the VisionSOM-6ULx module)
	UART4 TX (75 pin of the VisionSOM-6ULx module)		UART4 TX (75 pin of the VisionSOM-6ULx module)
	The new pins need to be defined in the ''~~imx6ul~~-~~evk~~'' section of the ''iomux'' configuration:		The new pins need to be defined in the ''visioncb-6ull'' section of the ''iomux'' configuration (''visioncb-6ull-std.dtsi'' file):
	<pre>pinctrl_uart4: uart4grp {		<pre>pinctrl_uart4: uart4grp {
	fsl,pins = <		fsl,pins = <
Line 135:		Line 147:
	The CROSS_COMPILE environmental variable should be set according to the cross compiler installation path.		The CROSS_COMPILE environmental variable should be set according to the cross compiler installation path.

	The compiled device tree blob files:		The are compiled device tree blob files:
	*~~somlabs-visionsom~~-6ull~~.dtb~~		* visioncb-6ull-std-emmc-btwifi.dtb
	*somlabs-~~visionsom~~-~~6ull~~-~~emmc~~.dtb		* visioncb-6ull-std-emmc.dtb
	*~~somlabs~~-~~visionsom~~-~~6ull~~-~~nand~~.dtb		* visioncb-6ull-std-sd-btwifi.dtb
	or		* visioncb-6ull-std-sd.dtb
	*~~somlabs~~-~~visionsom-6ul.dtb~~
	*somlabs-~~visionsom~~-~~6ul~~-~~emmc~~.dtb
	*~~somlabs~~-~~visionsom~~-~~6ul~~-~~nand~~.dtb

	may be copied to the ''/boot'' directory of the VisionSOM module storage memory overwriting the existing ones.		Two of them - with or without the wireless modem support - may be copied to the ''/boot'' directory of the VisionSOM module storage memory overwriting the existing ones (''visionsom-6ull.dtb'' and ''visionsom-6ull-emmc.dtb'').

	'''NOTE!''' It is strongly recommended to check startup messages after loading the device tree. If one of I/O lines is requested by more than one driver then you will get message like the one below:		'''NOTE!''' It is strongly recommended to check startup messages after loading the device tree. If one of I/O lines is requested by more than one driver then you will get message like the one below:

KrzysztofChojnowski at 12:34, 2 November 2019

2019-11-02T12:34:26Z

← Older revision		Revision as of 12:34, 2 November 2019
Line 2:		Line 2:
	Linux version 3.5.7 and newer include a new feature - device trees, they represent connections and structure of the machine it is run on. Modules used in earlier kernels are replaced with Device Tree Blobs (DTB).		Linux version 3.5.7 and newer include a new feature - device trees, they represent connections and structure of the machine it is run on. Modules used in earlier kernels are replaced with Device Tree Blobs (DTB).

	The device tree for VisionSOM-6ULL module is located in the file: somlabs-visionsom-6ull.dts (somlabs-visionsom-6ul.dts for VisionSOM-6UL) located within the Linux kernel source (arch/arm/boot/dts). This file should be edited in order to configure the hardware.		The device tree for VisionSOM-6ULL module is located in the file: somlabs-visionsom-6ull.dts (somlabs-visionsom-6ul.dts for VisionSOM-6UL) located within the Linux kernel source (arch/arm/boot/dts). This file should be edited in order to configure the hardware. Obtaining and building the Linux kernel is described in the [[Customizing the Linux kernel]] article.

	== GPIO pins definitions ==		== GPIO pins definitions ==

KrzysztofChojnowski: Created page with "{{PageHeader|Customizing the device tree}} toc Linux version 3.5.7 and newer include a new feature - device trees, they represent connections and structure of the machine..."

2019-11-01T11:48:04Z

Created page with "{{PageHeader|Customizing the device tree}} __toc__ Linux version 3.5.7 and newer include a new feature - device trees, they represent connections and structure of the machine..."

New page

{{PageHeader|Customizing the device tree}} __toc__
Linux version 3.5.7 and newer include a new feature - device trees, they represent connections and structure of the machine it is run on. Modules used in earlier kernels are replaced with Device Tree Blobs (DTB).

The device tree for VisionSOM-6ULL module is located in the file: somlabs-visionsom-6ull.dts (somlabs-visionsom-6ul.dts for VisionSOM-6UL) located within the Linux kernel source (arch/arm/boot/dts). This file should be edited in order to configure the hardware.

== GPIO pins definitions ==

Each pin definition in the dts file has three parts. First is the physical pad name (for example '''MX6UL_PAD_UART5_RX_DATA'''__I2C2_SDA 0x4001b8b0), second one is selected pin function (for example MX6UL_PAD_UART5_RX_DATA__'''I2C2_SDA''' 0x4001b8b0). All possible combinations are defined in kernel sources: arch/arm/boot/dts/imx6ul-pinfunc.h. The third part (for example MX6UL_PAD_UART5_RX_DATA__I2C2_SDA '''0x4001b8b0''') can be used to perform additional pin configuration, its bits are defined as follows (kernel docummentation: Documentation/devicetree/bindings/pinctrl/fsl,imx6ul-pinctrl.txt):

<pre>PAD_CTL_HYS (1 << 16)
PAD_CTL_PUS_100K_DOWN (0 << 14)
PAD_CTL_PUS_47K_UP (1 << 14)
PAD_CTL_PUS_100K_UP (2 << 14)
PAD_CTL_PUS_22K_UP (3 << 14)
PAD_CTL_PUE (1 << 13)
PAD_CTL_PKE (1 << 12)
PAD_CTL_ODE (1 << 11)
PAD_CTL_SPEED_LOW (0 << 6)
PAD_CTL_SPEED_MED (1 << 6)
PAD_CTL_SPEED_HIGH (3 << 6)
PAD_CTL_DSE_DISABLE (0 << 3)
PAD_CTL_DSE_260ohm (1 << 3)
PAD_CTL_DSE_130ohm (2 << 3)
PAD_CTL_DSE_87ohm (3 << 3)
PAD_CTL_DSE_65ohm (4 << 3)
PAD_CTL_DSE_52ohm (5 << 3)
PAD_CTL_DSE_43ohm (6 << 3)
PAD_CTL_DSE_37ohm (7 << 3)
PAD_CTL_SRE_FAST (1 << 0)
PAD_CTL_SRE_SLOW (0 << 0)</pre>

You can also use 0x80000000 value, then default pin configuration will be used.

== GPIO Input==

In this example the following pins are configured as inputs:
*GPIO1_IO08 (45 pin of the VisionSOM-6ULx module)
*GPIO1_IO09 (56 pin of the VisionSOM-6ULx module)

These pins are connected to the IO8 and IO9 buttons on the VisionCB-STB board.

Both pins need to be configured in the device tree file. In this example a new section of the ''imx6ul-evk'' entry is created:

<pre>pinctrl_gpio_in: gpioingrp {
fsl,pins = <
MX6UL_PAD_GPIO1_IO08__GPIO1_IO08 0x1b0b0
MX6UL_PAD_GPIO1_IO09__GPIO1_IO09 0x1b0b0
>;
};</pre>

This definition needs to be also linked to the ''iomux'' entry:
<pre>&iomuxc {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_hog_1 &pinctrl_gpio_in>;</pre>

Now, both inputs may be used by exporting the pins:
<pre>
echo 8 > /sys/class/gpio/export
echo 9 > /sys/class/gpio/export
</pre>

setting them as inputs:

<pre>
echo in > /sys/class/gpio/gpio8/direction
echo in > /sys/class/gpio/gpio9/direction
</pre>

and reading the input value:

<pre>
cat /sys/class/gpio/gpio8/value
cat /sys/class/gpio/gpio9/value
</pre>

== I2C ==
Adding a new I2C interface requires defining a new section in the dts file:
<pre>&i2c2 {
clock_frequency = <100000>;
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_i2c2>;
status = "okay";
};</pre>

Second step is the definition of the new pins in the ''iomux'' section (pinctrl_i2c2):
<pre>&iomuxc {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_hog_1>;
imx6ul-evk {

...
...

pinctrl_i2c2: i2c2grp {
fsl,pins = <
MX6UL_PAD_UART5_TX_DATA__I2C2_SCL 0x4001b8b0
MX6UL_PAD_UART5_RX_DATA__I2C2_SDA 0x4001b8b0
>;
}

...
...

};</pre>

== UART ==

In this example the UART4 port is added with the following signals:
UART4 RX (77 pin of the VisionSOM-6ULx module)
UART4 TX (75 pin of the VisionSOM-6ULx module)
The new pins need to be defined in the ''imx6ul-evk'' section of the ''iomux'' configuration:
<pre>pinctrl_uart4: uart4grp {
fsl,pins = <
MX6UL_PAD_UART4_TX_DATA__UART4_DCE_TX 0x1b0b1
MX6UL_PAD_UART4_RX_DATA__UART4_DCE_RX 0x1b0b1
>;
};</pre>

After that, the new port may be added as a new section in the device tree file:

<pre>&uart4 {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_uart4>;
status = "okay";
};</pre>

After system boot, the new port will be visible as the /dev/ttymxc3 file.

== Building device tree ==

After finishing the customization of the device tree it can be built from the main kernel directory by calling:

<pre>make ARCH=arm CROSS_COMPILE=<compiler_path> dtbs</pre>

The CROSS_COMPILE environmental variable should be set according to the cross compiler installation path.

The compiled device tree blob files:
*somlabs-visionsom-6ull.dtb
*somlabs-visionsom-6ull-emmc.dtb
*somlabs-visionsom-6ull-nand.dtb
or
*somlabs-visionsom-6ul.dtb
*somlabs-visionsom-6ul-emmc.dtb
*somlabs-visionsom-6ul-nand.dtb

may be copied to the ''/boot'' directory of the VisionSOM module storage memory overwriting the existing ones.

'''NOTE!''' It is strongly recommended to check startup messages after loading the device tree. If one of I/O lines is requested by more than one driver then you will get message like the one below:
<pre>[ 0.322774] imx6ul-pinctrl 20e0000.iomuxc: pin MX6UL_PAD_JTAG_TCK already requested by 20e0000.iomuxc; cannot claim for 20f4000.pwm
[ 0.322821] imx6ul-pinctrl 20e0000.iomuxc: pin-21 (20f4000.pwm) status -22
[ 0.322859] imx6ul-pinctrl 20e0000.iomuxc: could not request pin 21 (MX6UL_PAD_JTAG_TCK) from group pwm6grp on device 20e0000.iomuxc</pre>

Customizing the device tree - Revision history

KrzysztofChojnowski at 10:48, 30 June 2021

KrzysztofChojnowski at 12:52, 21 August 2020

KrzysztofChojnowski at 12:34, 2 November 2019

KrzysztofChojnowski: Created page with "{{PageHeader|Customizing the device tree}} __toc__ Linux version 3.5.7 and newer include a new feature - device trees, they represent connections and structure of the machine..."

KrzysztofChojnowski: Created page with "{{PageHeader|Customizing the device tree}} toc Linux version 3.5.7 and newer include a new feature - device trees, they represent connections and structure of the machine..."