如何在NXP源码基础上适配ELF 1开发板的PWM功能

elf@ubuntu:~/work$ tar jvxf linux-imx-imx_4.1.15_2.0.0_ga.tar.bz2
elf@ubuntu:~/work$ cd linux-imx-imx_4.1.15_2.0.0_ga/
elf@ubuntu:~/work/linux-imx-imx_4.1.15_2.0.0_ga$ ls

将arch/arm/configs路径下的imx_v7_mfg_defconfig复制一份，命名为imx6ull_elf1_defconfig

elf@ubuntu:~/work/linux-imx-imx_4.1.15_2.0.0_ga$ cp arch/arm/configs/imx_v7_mfg_defconfig arch/arm/configs/imx6ull_elf1_defconfig

将arch/arm/boot/dts路径下的imx6ull-14x14-evk.dts复制一份，命名为imx6ull-elf1-emmc.dts

elf@ubuntu:~/work/linux-imx-imx_4.1.15_2.0.0_ga$ cp arch/arm/boot/dts/imx6ull-14x14-evk.dts arch/arm/boot/dts/imx6ull-elf1-emmc.dts

elf@ubuntu:~/work/linux-imx-imx_4.1.15_2.0.0_ga$ vi arch/arm/boot/dts/Makefile

elf@ubuntu:~/work/linux-imx-imx_4.1.15_2.0.0_ga$ vim build.sh

#!/bin/bash
export CPUS=`grep -c processor /proc/cpuinfo` 
source /opt/fsl-imx-x11/4.1.15-2.0.0/environment-setup-cortexa7hf-neon-poky-linux-gnueabi
make distclean
make imx6ull_elf1_defconfig
make -j${CPUS}
rm -rf ./.tmp
make modules_install INSTALL_MOD_PATH=./.tmp/rootfs/
cd .tmp/rootfs/
tar -jcvf modules.tar.bz2 *

elf@ubuntu:~/work/linux-imx-imx_4.1.15_2.0.0_ga$ chmod 777 build.sh

从上图可以看出PWM2连接到了连接器的65脚。接下来我们需要找到这个引脚在软件上的信号名称。

打开ELF 1开发板资料包5-硬件资料5-4 管脚分配表ELF 1引脚复用对照表找到65引脚的信号名称。

pinctrl_pwm2: pwm2grp {
                        fsl,pins = <
                             MX6UL_PAD_GPIO1_IO09__PWM2_OUT   0x110b0
                        >;
                };

在设备树文件arch/arm/boot/dts/imx6ull.dtsi中已经定义好了8路PWM信号的相关节点，只需要将PWM2的时钟配置上即可，将clocks属性的IMX6UL_CLK_DUMMY更改为IMX6UL_CLK_PWM2。

&pwm2 {
        pinctrl-names = "default";
        pinctrl-0 = <&pinctrl_pwm2>;
        status = "okay";
};

由于pwm只涉及到设备树修改，不再使用脚本编译，单独编译设备树即可。

elf@ubuntu:~/work/linux-imx-imx_4.1.15_2.0.0_ga$ . /opt/fsl-imx-x11/4.1.15-2.0.0/environment-setup-cortexa7hf-neon-poky-linux-gnueabi
elf@ubuntu:~/work/linux-imx-imx_4.1.15_2.0.0_ga$ make dtbs

elf@ubuntu:~/work/linux-imx-imx_4.1.15_2.0.0_ga$ scp arch/arm/boot/dts/imx6ull-elf1-emmc.dtb root@172.16.0.175:/run/media/mmcblk1p1/

root@ELF1~# sync
root@ELF1~# reboot

待开发板启动完成，将PWM2设置为输出

root@ELF1:~#:~# echo 0 > /sys/class/pwm/pwmchip1/export

root@ELF1:~#:~# echo 1 > /sys/class/pwm/pwmchip1/pwm0/enable

root@ELF1:~#:~# echo 1000000 > /sys/class/pwm/pwmchip1/pwm0/period

root@ELF1:~#:~# echo 500000 > /sys/class/pwm/pwmchip1/pwm0/duty_cycle

root@ELF1:~#:~# echo 0 > /sys/class/pwm/pwmchip1/pwm0/enable