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Locating configuration file
The initial CPU configuration is part the following device tree source file:
- arch/arm/boot/dts/imx53.dtsi
Shared module configuration can be found in the following file:
- arch/arm/boot/dts/imx53-vmx53.dtsi
The specific module configuration customised for i.MX53 SODIMM PC Module is part of these device tree source files:
- i.MX53 SODIMM PC Module Max: arch/arm/boot/dts/imx53-vmx53-557.dts
- i.MX53 SODIMM PC Module Pro: arch/arm/boot/dts/imx53-vmx53-668.dts
- i.MX53 SODIMM PC Module Basic: arch/arm/boot/dts/imx53-vmx53-779.dts
Note: In most cases just a single file edit is needed to apply modifications.
Definition of configuration macros
PAD_CTL_HVE (1 << 13) PAD_CTL_HYS (1 << 8) PAD_CTL_PKE (1 << 7) PAD_CTL_PUE (1 << 6) PAD_CTL_PUS_100K_DOWN (0 << 4) PAD_CTL_PUS_47K_UP (1 << 4) PAD_CTL_PUS_100K_UP (2 << 4) PAD_CTL_PUS_22K_UP (3 << 4) PAD_CTL_ODE (1 << 3) PAD_CTL_DSE_LOW (0 << 1) PAD_CTL_DSE_MED (1 << 1) PAD_CTL_DSE_HIGH (2 << 1) PAD_CTL_DSE_MAX (3 << 1) PAD_CTL_SRE_FAST (1 << 0) PAD_CTL_SRE_SLOW (0 << 0)
Controlling GPIO signals using raw access
In this example signals CSI0_DAT12 - CSI0_DAT19 will be configured as GPIOs.
Note: Make sure signals MX53_PAD_CSI0_DAT12_* up to MX53_PAD_CSI0_DAT19_* are set only once in all related device tree source files.
Device tree modification:
&iomuxc {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_hog>;
imx53-vmx53 {
pinctrl_hog: hoggrp {
fsl,pins = <
MX53_PAD_CSI0_DAT12__GPIO5_30 0x80000000 // PAD default config
MX53_PAD_CSI0_DAT13__GPIO5_31 0x000000e0 // PKE + PUE + PUS_47K_UP + DSE_LOW + SRE_SLOW
MX53_PAD_CSI0_DAT14__GPIO6_0 0x00000100 // HYS + DSE_LOW + SRE_SLOW
MX53_PAD_CSI0_DAT15__GPIO6_1 0x000000c0 // PKE + PUE + PUS_100K_DOWN + DSE_LOW + SRE_SLOW
MX53_PAD_CSI0_DAT16__GPIO6_2 0x80000000 // PAD default config
MX53_PAD_CSI0_DAT17__GPIO6_3 0x80000000 // PAD default config
MX53_PAD_CSI0_DAT18__GPIO6_4 0x80000000 // PAD default config
MX53_PAD_CSI0_DAT19__GPIO6_5 0x80000000 // PAD default config
>;
};
}
Testing the modifications
Calculating GPIO number
GPIO pin numbering follows this general equation:
GPIO_NUMBER = MX53_PAD_NAME__GPIOX_Y = X_Y = (X-1)*32+Y
GPIO accessible from CSI0_DAT13 pin is available at this number:
GPIO_NUMBER = MX53_PAD_CSI0_DAT13__GPIO5_31 = 5_31 = (5-1)*32+31 = 4*32+31 = 159
Setting GPIO as output
root@vmx53 ~$ echo 159 > /sys/class/gpio/export
root@vmx53 ~$ echo out > /sys/class/gpio/gpio159/direction
root@vmx53 ~$ echo 0 > /sys/class/gpio/gpio159/value
#root@vmx53 ~$ echo 1 > /sys/class/gpio/gpio159/value
#root@vmx53 ~$ echo 159 > /sys/class/gpio/unexport
Setting GPIO as input
root@vmx53 ~$ echo 159 > /sys/class/gpio/export
root@vmx53 ~$ echo in > /sys/class/gpio/gpio159/direction
root@vmx53 ~$ cat /sys/class/gpio/gpio159/value
0
#root@vmx53 ~$ echo 159 > /sys/class/gpio/unexport
Controlling GPIO signals using drivers
Signals will be set accordingly:
- pins CSI0_DAT12 - CSI0_DAT14 as input GPIOs
- pins CSI0_DAT15 - CSI0_DAT17 as output GPIOs
Note: Make sure signals MX53_PAD_CSI0_DAT12_* up to MX53_PAD_CSI0_DAT17_* are set only once in all related device tree source files.
Device tree modification:
&iomuxc {
...
imx53-vmx53 {
...
pinctrl_inp: inpgrp {
fsl,pins = <
MX53_PAD_CSI0_DAT12__GPIO5_30 0x80000000 // PAD default config
MX53_PAD_CSI0_DAT13__GPIO5_31 0x80000000 // PAD default config
MX53_PAD_CSI0_DAT14__GPIO6_0 0x80000000 // PAD default config
>;
};
pinctrl_out: outgrp {
fsl,pins = <
MX53_PAD_CSI0_DAT15__GPIO6_1 0x80000000 // PAD default config
MX53_PAD_CSI0_DAT16__GPIO6_2 0x80000000 // PAD default config
MX53_PAD_CSI0_DAT17__GPIO6_3 0x80000000 // PAD default config
>;
};
...
};
...
}
Input signals
Adding GPIO kernel module
Device Drivers --->
Input device support --->
[*] Keyboards --->
<*> GPIO Buttons
Altering input sources in the device tree
/ {
...
inputs {
compatible = "gpio-keys";
#address-cells = <1>;
#size-cells = <0>;
autorepeat;
input@0 {
label = "input-0";
gpios = <&gpio5 30 GPIO_ACTIVE_HIGH>;
linux,code = <0x100>; // BTN_0
};
input@1 {
label = "input-1";
gpios = <&gpio5 31 GPIO_ACTIVE_HIGH>;
linux,code = <0x101>; // BTN_1
};
input@2 {
label = "input-2";
gpios = <&gpio6 0 GPIO_ACTIVE_HIGH>;
linux,code = <0x102>; // BTN_2
};
};
...
};
Testing the modifications
root@vmx53 ~$ evtest /dev/input/event4
Input driver version is 1.0.1
Input device ID: bus 0x19 vendor 0x1 product 0x1 version 0x100
Input device name: "inputs.12"
Supported events:
Event type 0 (EV_SYN)
Event type 1 (EV_KEY)
Event code 256 (BTN_0)
Event code 257 (BTN_1)
Event code 258 (BTN_2)
Properties:
Property type 20 (EV_REP)
Property code 0 (REP_DELAY)
Value 250
Property code 1 (REP_PERIOD)
Value 33
Testing ... (interrupt to exit)
Event: time 946946772.718139, type 1 (EV_KEY), code 256 (BTN_0), value 1
Event: time 946946772.718139, -------------- SYN_REPORT ------------
Event: time 946946772.968114, type 1 (EV_KEY), code 256 (BTN_0), value 2
Event: time 946946772.968114, -------------- SYN_REPORT ------------
Event: time 946946773.008115, type 1 (EV_KEY), code 256 (BTN_0), value 2
Event: time 946946773.008115, -------------- SYN_REPORT ------------
Event: time 946946773.018134, type 1 (EV_KEY), code 256 (BTN_0), value 0
Event: time 946946773.018134, -------------- SYN_REPORT ------------
Event: time 946946786.688130, type 1 (EV_KEY), code 256 (BTN_0), value 1
Event: time 946946786.688130, -------------- SYN_REPORT ------------
Event: time 946946786.908131, type 1 (EV_KEY), code 256 (BTN_0), value 0
Output signals
Adding GPIO kernel module
Device Drivers --->
[*] LED Support --->
<*> LED Class Support
<*> LED Support for GPIO connected LEDs
[*] LED Trigger support --->
Altering output sources in the device tree
/ {
...
outputs {
compatible = "gpio-leds";
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_out>;
output@0 {
label = "output-0";
gpios = <&gpio6 1 GPIO_ACTIVE_HIGH>;
default-state = "keep";
};
output@1 {
label = "output-1";
gpios = <&gpio6 2 GPIO_ACTIVE_HIGH>;
default-state = "on";
};
output@2 {
label = "output-2";
gpios = <&gpio6 3 GPIO_ACTIVE_HIGH>;
default-state = "off";
};
};
...
};
Testing the modifications
root@vmx53 ~$ cat /sys/class/leds/output-0/trigger
[none] nand-disk mmc0 mmc1 timer heartbeat backlight gpio default-on
root@vmx53 ~$ cat /sys/class/leds/output-0/brightness
0
root@vmx53 ~$ echo 255 > /sys/class/leds/output-0/brightness # On
root@vmx53 ~$ echo 0 > /sys/class/leds/output-0/brightness # Off
Printing the current state (brightness) of output signals:
root@vmx53 ~$ for i in /sys/class/leds/output-*/ ; do value=$(cat ${i}/brightness); echo $(basename ${i}) :: ${value}; done
output-0 :: 0
output-1 :: 255
output-2 :: 0
Debugging
root@vmx53 ~$ mount -t debugfs none /sys/kernel/debug
root@vmx53 ~$ cat /sys/kernel/debug/gpio
GPIOs 0-31, platform/53f84000.gpio, 53f84000.gpio:
gpio-7 (usbotg_vbus ) out lo
GPIOs 32-63, platform/53f88000.gpio, 53f88000.gpio:
gpio-48 (spi_imx ) out lo
gpio-49 (spi_imx ) out lo
gpio-52 (ads7846_pendown ) in hi
gpio-62 (spi_imx ) out lo
GPIOs 64-95, platform/53f8c000.gpio, 53f8c000.gpio:
gpio-83 (spi_imx ) out lo
gpio-88 (50004000.esdhc cd ) in hi
gpio-89 (50008000.esdhc cd ) in hi
gpio-93 (led-red ) out lo
gpio-95 (usbh1_vbus ) out lo
GPIOs 96-127, platform/53f90000.gpio, 53f90000.gpio:
GPIOs 128-159, platform/53fdc000.gpio, 53fdc000.gpio:
gpio-132 (LCD PEN ) out lo
gpio-158 (input-0 ) in lo
gpio-159 (input-1 ) in lo
GPIOs 160-191, platform/53fe0000.gpio, 53fe0000.gpio:
gpio-160 (input-2 ) in lo
gpio-161 (output-0 ) out lo
gpio-162 (output-1 ) out lo
gpio-163 (output-2 ) out lo
GPIOs 192-223, platform/53fe4000.gpio, 53fe4000.gpio: