Jeonghun (James) Lee

12/30/2020

Android PWM 과 GPIO 설정 및 Control Test App

1. Device Tree 관련설정

Device Tree 기본문법이해

https://elinux.org/Device_Tree_Usage

https://ahyuo79.blogspot.com/2018/04/raspberry-pi-device-tree-cmdline.html

https://ahyuo79.blogspot.com/2015/08/kernel-boot-kernel-device-tree.html

https://ahyuo79.blogspot.com/2015/08/device-tree.html

Device Tree 기반 부팅방법

https://ahyuo79.blogspot.com/2015/08/device-tree-2-am437xam335x.html

https://ahyuo79.blogspot.com/2015/08/am437x-kernel-device-tree.html

아래설정은 i.MX8에서 BSP에서 LSIO PWM 관련설정이 없어 어쩔수 없이 Datasheet를 보고 직접 만들어서 추가하였으며, MIPI에서 사용하는 PWM과 같이 i.mx27로 사용결정

$ vi *dts


/* PWM 사용을 위해서 PWM 사용과 GPIO PINMUX 설정 
iomuxc가 label 이므로  &iomuxc 사용 (iomuxc: pinctrl)  
*/

&iomuxc {
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_hog>;

	/* PINMUX 를 PWM과 GPIO 변경 
	*  IMX8QXP_UART1_RX  : PWM1
	*  IMX8QXP_UART1_TX  : GPIO 
	*/
	pinctrl_lppwm1: lppwm1grp {
		fsl,pins = <
			IMX8QXP_UART1_RX_LSIO_PWM1_OUT					0x00000020
			IMX8QXP_UART1_TX_LSIO_GPIO0_IO21				0x00000020		
		>;
	};
	/* PINMUX 를 PWM과 GPIO 변경 
	*  IMX8QXP_UART1_RTS_B  : PWM2 
	*  IMX8QXP_UART1_CTS_B  : GPIO
	*/
	pinctrl_lppwm2: lppwm2grp {
		fsl,pins = <
			IMX8QXP_UART1_RTS_B_LSIO_PWM2_OUT	0x00000020		
			IMX8QXP_UART1_CTS_B_LSIO_GPIO0_IO24	0x00000020	
		>;
	};	

};

/* MIPI의 PWM 부분 삭제 전부 label이므로 &적용  */

/delete-node/ &pwm_mipi_lvds0;
/delete-node/ &pwm_mipi_lvds1;

/delete-node/ &lvds_backlight0;
/delete-node/ &lvds_backlight1;

/* UART1 과 PWM PINMUX 충돌하여 미사용로 변경  */
&lpuart1 {
    status = "disabled";
};


/* 
    LSIO PWM 관련정의가 없어서 Datasheet를 보고 각 Address에 맞춰 정의
    MIPI도 i.MX6도 PWM을 im27-pwm 사용하여 나 또한 이것으로 사용하기로 결정 
    lsio_subsys를 main으로 넣기로함 

    / { 
    .....
     }
*/

/ {
	
	lsio_subsys: bus@5d000000 {
		compatible = "simple-bus";
		#address-cells = <1>;
		#size-cells = <1>;
		ranges = <0x5d000000 0x0 0x5d000000 0x1000000>,
			<0x08000000 0x0 0x08000000 0x10000000>;

/* 
i.MXQXP의 LSIO Datasheet 관련부분을 보면 상위 Memory Map Range 영역을 설정  
현재 child's address 1 , size 1만 존재 parent address가 없음 총 4개로 memory mapped io로 하는 것으로 생각됨 (추측)
- Physical Start 0x5d000000 0x0 
- Physical End   0x5d000000+0x1000000
- Virtual  Start 0x08000000 0x0
- Virtual  End   0x08000000+0x10000000
*/

		pwm1_lsio: pwm@5d010000 {
			compatible = "fsl,imx8qxp-pwm", "fsl,imx27-pwm";
			reg = <0x5d010000 0x1000>;
			clocks = <&pwm1_lpcg 0>,
				 <&pwm1_lpcg 1>,
				 <&pwm1_lpcg 2>;				
			pinctrl-names = "default";
			pinctrl-0 = <&pinctrl_lppwm1>;					 
			clock-names = "per", "ipg","32k";
			assigned-clocks = <&clk IMX_SC_R_PWM_1 IMX_SC_PM_CLK_PER>;
			assigned-clock-rates = <24000000>
			#pwm-cells = <2>
			power-domains = <&pd IMX_SC_R_PWM_1>;
			status = "okay";
		};	

		pwm2_lsio: pwm@5d020000 {
			compatible = "fsl,imx8qxp-pwm", "fsl,imx27-pwm";
			reg = <0x5d020000 0x1000>;
			clocks = <&pwm2_lpcg 0>,
				 <&pwm2_lpcg 1>,
				 <&pwm2_lpcg 2>;				
			pinctrl-names = "default";
			pinctrl-0 = <&pinctrl_lppwm2>;					 
			clock-names = "per", "ipg","32k";
			assigned-clocks = <&clk IMX_SC_R_PWM_2 IMX_SC_PM_CLK_PER>;
			assigned-clock-rates = <24000000>;
			#pwm-cells = <2>;
			power-domains = <&pd IMX_SC_R_PWM_2>;
			status = "okay";
		};	

	};

//#pwm-cells   pwm 기반으로 사용하는 다른 driver에서 이를 사용  (backlight) 
https://www.kernel.org/doc/Documentation/devicetree/bindings/pwm/pwm.txt
https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bindings/pwm/pwm.txt

};

2. PWM Driver 기본구조분석

PWM Driver 기본구조 및 sys filesystem 사용법

https://www.kernel.org/doc/html/latest/driver-api/pwm.html

PWM Driver (imx27)

pwmchip_add()
pwmchip_remove()

i.MX27 PWM Driver

https://github.com/torvalds/linux/blob/master/drivers/pwm/core.c

https://github.com/torvalds/linux/blob/master/drivers/pwm/pwm-imx27.c

PWM 기반의 Driver (Back light)

pwm_request() 기반으로 구현

2.1 sys filesystem PWM-TEST

상위 imx27 Driver가 설정과 Clock 설정한 후 아래와 같이 설정가능하지만, 권한이 문제발생하여 아래와 같이 su 를 이용하여 root로 테스트

PWM0 생성 및 기본제어방법

GPIO와 유사하게 export로 설정후 pwm0을 생성되어 자동마운트 된후 실제적인 설정진행

period : 주기를 설정 ( ns 단위)
duty_cycle: positive pulse width (ns 단위)

$ su 
# id
uid=0(root) gid=0(root) groups=0(root),1007(log),3009(readproc) context=u:r:su:s0

$ echo 0 > /sys/class/pwm/pwmchip0/export   // pwm0 생성됨 
$ echo 1000000 > /sys/class/pwm/pwmchip0/pwm0/period
$ echo 500000 > /sys/class/pwm/pwmchip0/pwm0/duty_cycle
$ echo 1 > /sys/class/pwm/pwmchip0/pwm0/enable

상위 설정은 1KHz의 주기를 가지고 Duty 즉, High Pulse는 반으로 설정

아래와 같이 50Hz 주기 설정 후 half duty로 변경 및 다양한 duty 테스트

//50Hz 20ms 주기 설정  
$ echo 20000000 > /sys/class/pwm/pwmchip0/pwm0/period 

//10000us (10ms) (half) Positive Pulse 
$ echo 10000000 > /sys/class/pwm/pwmchip0/pwm0/duty_cycle 

//1000 us (1ms)
$ echo 1000000 > /sys/class/pwm/pwmchip0/pwm0/duty_cycle 

//1250 us (1.25ms) 
$ echo 1250000 > /sys/class/pwm/pwmchip0/pwm0/duty_cycle 

//1500 us (1.5ms)
$ echo 1500000 > /sys/class/pwm/pwmchip0/pwm0/duty_cycle 

//1750 us (1.75ms) 
$ echo 1750000 > /sys/class/pwm/pwmchip0/pwm0/duty_cycle 

//2000 us (2.ms)
$ echo 2000000 > /sys/class/pwm/pwmchip0/pwm0/duty_cycle

https://developer.toradex.com/knowledge-base/pwm-linux

https://sunplus-tibbo.atlassian.net/wiki/spaces/doc/pages/761921537/How+to+setup+and+use+PWM+on+SP7021+demo+board+V3

상위는 Android의 기본 shell에서 동작않아, 이를 해결하기 위해서 init.rc 에서 export 와 권한설정하기로 결정.

http://wiki.lemaker.org/Use_Java_to_control_GPIO_on_Android

https://source.android.com/compatibility/tests

2.2 Android init.hardware.rc 문법 수정

Linux로 말하면, init script 이며, 이는 이부분 각 service와 초기화 관련부분을 담당

init.rc
init.%hardware%.rc

Android Init 관련문법 복습

Init 문법을 보면 크게 Action 과 Service 와 command 나누어지며, 다음과 같이 동작한다.

//Action 기능 이며, trigger 와 command를 다양하게 지원
on <trigger> [&& <trigger>]*
   <command>
   <command>
   <command>
   
//Service 기능이며 관련 option은 아래 링크 참조      
service <name> <pathname> [ <argument> ]*
   <option>
   <option>
   ...

Android init 문법의 세부내용 Manual

https://android.googlesource.com/platform/system/core/+/master/init/README.md

http://www.dreamy.pe.kr/zbxe/CodeClip/164851

http://www.eastsky.co.kr/Android_Board/4982

https://community.nxp.com/t5/i-MX-Processors-Knowledge-Base/What-is-inside-the-init-rc-and-what-is-it-used-for/ta-p/1106360

Android의 기본 init.rc 확인

기본 init.rc 위치 및 설정확인하였지만, 직접수정하지 않는 것이 좋을 것 같아 이부분은 그대로 유지

$ vi system/core/rootdir/init.rc  // 
import /init.environ.rc
import /init.usb.rc
import /init.${ro.hardware}.rc
import /vendor/etc/init/hw/init.${ro.hardware}.rc
import /init.usb.configfs.rc
import /init.${ro.zygote}.rc

# Cgroups are mounted right before early-init using list from /etc/cgroups.json
on early-init
    # Disable sysrq from keyboard
    write /proc/sys/kernel/sysrq 0

    # Set the security context of /adb_keys if present.
    restorecon /adb_keys

    # Set the security context of /postinstall if present.
    restorecon /postinstall

    mkdir /acct/uid
.........    

$ cat out/target/product/mek_8q/root/init.rc

i.MX8을 위한 init.hardware.rc 에 수정

각 hardware를 위한 init.rc 부분에 아래와 pwm관련설정부분을 추가를 해준다.

상위 문법을 보면 trigger 로 조건이 맞을 경우 command로 action이 되어진다.

$ vi ./device/fsl/imx8q/mek_8q/init.imx8qxp.rc
......
    # jhlee /sys filesystem mount가 된 경우 실행 
on property:sys.boot_completed=1
    #jhlee for PWM1/2  root 권한으로 실행됨  
    chmod 0777 /sys/class/pwm/pwmchip0
    chmod 0222 /sys/class/pwm/pwmchip0/export
    chmod 0222 /sys/class/pwm/pwmchip0/unexport
    chmod 0777 /sys/class/pwm/pwmchip1
    chmod 0222 /sys/class/pwm/pwmchip1/export
    chmod 0222 /sys/class/pwm/pwmchip1/unexport

    # PWM1 50Hz 20ms / 10ms (half)
    write /sys/class/pwm/pwmchip0/export 0
    write /sys/class/pwm/pwmchip0/pwm0/enable 1
    write /sys/class/pwm/pwmchip0/pwm0/period 20000000
    write /sys/class/pwm/pwmchip0/pwm0/duty_cycle 10000000

    # PWM2 50Hz 20ms / 10ms (half)
    write /sys/class/pwm/pwmchip1/export 0
    write /sys/class/pwm/pwmchip1/pwm0/enable 1
    write /sys/class/pwm/pwmchip1/pwm0/period 20000000
    write /sys/class/pwm/pwmchip1/pwm0/duty_cycle 10000000

    chmod 0666 /sys/class/pwm/pwmchip0/pwm0/period
    chmod 0666 /sys/class/pwm/pwmchip0/pwm0/duty_cycle
    chmod 0666 /sys/class/pwm/pwmchip0/pwm0/enable

    chmod 0666 /sys/class/pwm/pwmchip1/pwm0/period
    chmod 0666 /sys/class/pwm/pwmchip1/pwm0/duty_cycle
    chmod 0666 /sys/class/pwm/pwmchip1/pwm0/enable

    # GPIO UART1_TX 21
    write /sys/class/gpio/export 21
    write /sys/class/gpio/gpio21/direction "out"
    write /sys/class/gpio/gpio21/value 1

    # GPIO UART1_CTS_B 24
    write /sys/class/gpio/export 24
    write /sys/class/gpio/gpio24/direction "out"
    write /sys/class/gpio/gpio24/value 1

    chmod 0666 /sys/class/gpio/export
    chmod 0666 /sys/class/gpio/unexport
    chmod 0666 /sys/class/gpio/gpio21/direction
    chmod 0666 /sys/class/gpio/gpio21/value
    chmod 0666 /sys/class/gpio/gpio24/direction
    chmod 0666 /sys/class/gpio/gpio24/value
....    

$ cat out/target/product/mek_8q/vendor/etc/init/hw/init.freescale.imx8qxp.rc   // 빌드 후 실제 적용되어되었는지확인

init.rc script이 root기반으로 동작되기 때문에 초반에 chmod를 하는것은 의미가 없다

2.3 PWM ueventd.rc 문법 수정

처음 착각했던 것이 export를 값을 넣어주면, uevent가 발생하여 관련부분이 pwm이 생기면서 이 script를 이용하여 permission을 변경할 줄 알았다.

ueventd.rc
ueventd.%hardware%.rc

uevend.rc script 기본이해

https://android.googlesource.com/platform/system/core/+/master/init/README.ueventd.md

https://android.googlesource.com/device/google/marlin/+/cf1b301966adfba778a55816cabf4cb22f0b2632/ueventd.common.rc

ueventd.rc 설정

아래설정으로 하면 될 줄 알았는데, 실패했지만, 될 것이라고 생각되어 이곳에 기록하며 추후 재확인

$ vi ./device/fsl/imx8q/mek_8q/ueventd.freescale.rc
# /sys file은 entry 5개 (주의)
# /dev file은 entry 4개 
# jhlee for pwmchip0 pwm0
/sys/devices/platform/bus@5d000000/5d010000.pwm/pwm/pwmchip0/pwm0  enable 0666 system system
/sys/devices/platform/bus@5d000000/5d010000.pwm/pwm/pwmchip0/pwm0  period 0666 system system
/sys/devices/platform/bus@5d000000/5d010000.pwm/pwm/pwmchip0/pwm0  duty_cycle 0666 system system
/sys/devices/platform/bus@5d000000/5d010000.pwm/pwm/pwmchip0/pwm0  polarity   0666 system system

# jhlee for pwmchip1 pwm0
/sys/devices/platform/bus@5d000000/5d020000.pwm/pwm/pwmchip1/pwm0  enable 0666 system system
/sys/devices/platform/bus@5d000000/5d020000.pwm/pwm/pwmchip1/pwm0  period 0666 system system
/sys/devices/platform/bus@5d000000/5d020000.pwm/pwm/pwmchip1/pwm0  duty_cycle 0666 system system
/sys/devices/platform/bus@5d000000/5d020000.pwm/pwm/pwmchip1/pwm0  polarity   0666 system system

# jhlee for pwm (0/1/2/3)
/sys/class/pwm/pwmchip*      export     0666 system system
/sys/class/pwm/pwmchip*      unexport   0666 system system
/sys/class/pwm/pwmchip*      enable     0666 system system
/sys/class/pwm/pwmchip*      period     0666 system system
/sys/class/pwm/pwmchip*      duty_cycle 0666 system system
/sys/class/pwm/pwmchip*      polarity   0666 system system

$ cat out/target/product/mek_8q/vendor/ueventd.rc  // /sys file은 entry 5개 사용 주의 
[    5.133113] ueventd: /vendor/ueventd.rc: 44: /sys/ lines must have 5 entries
[    5.140349] ueventd: /vendor/ueventd.rc: 45: /sys/ lines must have 5 entries
[    5.147472] ueventd: /vendor/ueventd.rc: 46: /sys/ lines must have 5 entries
[    5.154572] ueventd: /vendor/ueventd.rc: 47: /sys/ lines must have 5 entries

ueventd.rc pwm 과 gpio 관련예제

https://gitlab.peslerbe.com/peslerbe/rk3399-android-8.1/-/commit/aabec8cf909cdd25598ab3c190774f52c9ceb077

ueventd 별도정리 필요

ueventd 의 동작의 이해와 udev 와 차이

https://lixiaogang03.github.io/2020/01/08/Android-Uevent/

https://seokbeomkim.github.io/posts/android_uevent_and_ueventd/

https://kshokd.wordpress.com/2012/08/29/init-%EA%B3%BC%EC%A0%95%EC%97%90%EC%84%9C-uevent%EC%99%80-ueventd%EC%9D%98-%ED%99%9C%EC%9A%A9/

android ueventd Main 소스

https://android.googlesource.com/platform/system/core/+/master/init/ueventd.cpp

ueventd.rc Parser 소스

ParseConfig (ueventd.rc ) -> AddSingleLineParser->ParsePermissionsLine (각 sys or dev parsing 후 permision 설정 )

(sys 와 dev는 entry 갯수가 다르며, 이는 Cold boot를 위한 것이므로, Kernel에서 미리 설정되어야 한다)

https://android.googlesource.com/platform/system/core/+/master/init/ueventd_parser.cpp

ueventd의 handler 소스

실제동작을 LOG_UEVENTS로 DEBUG 가능

https://android.googlesource.com/platform/system/core/+/master/init/uevent_listener.cpp

ueventd debug 방법

상위 ueventd 소스를 보면 LOG_UEVENTS 설정에 따라 LOG를 볼 수 있으며 이를 강제로 선언하여 Debug를 한다.

$ vi ./system/core/init/Android.mk 
.......
init_options += -DLOG_UEVENTS=1 \
    -DSEPOLICY_VERSION=$(POLICYVERS)
.......

https://android.googlesource.com/platform/system/core/+/18ccc1b%5E!/

ueventd의 selinux 설정

https://android.googlesource.com/platform/system/sepolicy/+/master/public/ueventd.te

PWM의 sysfs의 구조

https://github.com/torvalds/linux/blob/master/drivers/pwm/sysfs.c

DEVICE_ATTR

DEVICE_ATTR_RW

DEVICE_ATTR_RO

DEVICE_ATTR_WO

device_attribute

https://elixir.bootlin.com/linux/latest/source/include/linux/device.h#L130

https://www.kernel.org/doc/Documentation/filesystems/sysfs.txt

root 권한으로 shell 에서 pwm 위치 찾기

$ for i in /sys/class/pwm*/pwmchip*/pwm* ; do ls -l $i; cat $i; done
total 0
-r--r--r-- 1 root root 4096 2021-01-20 07:16 capture
-r--r--r-- 1 root root 4096 2021-01-20 07:16 consumers
-rw-rw-rw- 1 root root 4096 2021-01-20 03:33 duty_cycle
-rw-rw-rw- 1 root root 4096 2021-01-20 03:33 enable
-r--r--r-- 1 root root 4096 2021-01-20 07:16 output_type
-rw-rw-rw- 1 root root 4096 2021-01-20 03:33 period
-rw-r--r-- 1 root root 4096 2021-01-20 07:16 polarity
drwxr-xr-x 2 root root    0 2021-01-20 07:16 power
-r--r--r-- 1 root root 4096 2021-01-20 07:16 suppliers
-rw-r--r-- 1 root root 4096 2021-01-20 07:16 uevent
cat: /sys/class/pwm/pwmchip0/pwm0: Is a directory
total 0
-r--r--r-- 1 root root 4096 2021-01-20 07:17 capture
-r--r--r-- 1 root root 4096 2021-01-20 07:17 consumers
-rw-rw-rw- 1 root root 4096 2021-01-20 03:33 duty_cycle
-rw-rw-rw- 1 root root 4096 2021-01-20 03:33 enable
-r--r--r-- 1 root root 4096 2021-01-20 07:17 output_type
-rw-rw-rw- 1 root root 4096 2021-01-20 03:33 period
-rw-r--r-- 1 root root 4096 2021-01-20 07:17 polarity
drwxr-xr-x 2 root root    0 2021-01-20 07:17 power
-r--r--r-- 1 root root 4096 2021-01-20 07:17 suppliers
-rw-r--r-- 1 root root 4096 2021-01-20 07:17 uevent
cat: /sys/class/pwm/pwmchip1/pwm0: Is a directory

$ ls -alh /sys/class/pwm/          //ueventd.*.rc에 추가하 위해서 정확한 PATH 알기 (아래는 강제로 권한변경된 상태)
...
lrwxrwxrwx  1 root root 0 2020-12-30 06:06 pwmchip0 -> ../../devices/platform/bus@5d000000/5d010000.pwm/pwm/pwmchip0
lrwxrwxrwx  1 root root 0 2020-12-30 06:06 pwmchip1 -> ../../devices/platform/bus@5d000000/5d020000.pwm/pwm/pwmchip1

2.4 SELinux

i.MX8의 의 SElinux 문제발생 (동작안됨)

상위에서 write /sys/class/pwm/pwmchip0/export 0 할 경우 uevent가 발생할것이며, 아래와 같이 ls를 했을 경우 access 문제발생

mek_8q:/sys/class/pwm/pwmchip0 $ ls -alh
drwxr-xr-x 3 root root    0 1970-01-01 00:00 .[  175.487816] type=1400 audit(1609308473.916:27): avc: denied { getattr } for comm="ls" path="/sys/devices/platform/bus@5d000000/5d020000.pwm/pwm/pwmchip0/uevent" dev="sysfs" ino=34845 scontext=u:r:shell:s0 tcontext=u:object_r:sysfs:s0 tclass=file permissive=1

BoardConfig.mk 관련수정

SElinux 를 허용모드(permissive) 강제로 변경후 별도의 추가 *.te를 할 필요가 없으므로 이를 간단히 해결

$ find . -name BoardConfig.mk  // 기본위치파악 
device/Vendor/ARCH/BoardName/BoardConfig.mk

$ vi ./device/fsl/imx8q/mek_8q/BoardConfig.mk    // i.MX8 관련수정 

# NXP의 기본 Hardware 설정 
# NXP default config
BOARD_KERNEL_CMDLINE := init=/init androidboot.hardware=freescale firmware_class.path=/vendor/firmware loop.max_part=7

#
# permissive 추가 
BOARD_KERNEL_CMDLINE += androidboot.selinux=permissive

상위와 같이 permissive 로 변경할 경우, 상위와 같이 error는 발생하며, 경고는 하지만, 문제가 되지 않음

하지만, 이는 개발시에는 사용해야하면, 제품 출하시에는 반드시 관련부분을 수정해야한다.

Android SELinux (일반 Linux의 SELinux의 사용법과 좀 다름)

https://source.android.com/security/selinux

3. Android SDK/NDK/PDK 구분