gpio模擬pwm訊號（風扇轉速控制）
阿新 • • 發佈：2021-06-21
一、需求：
四路風扇分別通過PA6\PG9\PG11\PG12四個腳輸出pwm訊號，控制風扇風速。但是晶片這4個腳沒用硬體PWM功能，所以必須使用io口模擬pwm時序。 主要通過高精度定時器hrtimer去模擬pwm時序
二、功能實現
1、dts檔案註冊pwm裝置
gpio-pwms {
compatible = "gpio-pwms";
pinctrl-names = "default";
pwm1 {
label = "pwm1";
gpios = <&pio 0 6 GPIO_ACTIVE_HIGH>; //GPIO6 ---> PA6
};
pwm2 {
label = "pwm2";
gpios = <&pio 6 9 GPIO_ACTIVE_HIGH>; //GPIO201 ---->PG9
};
pwm3{
label = "pwm3";
gpios = <&pio 6 11 GPIO_ACTIVE_HIGH>; //GPIO203 ----->PG11
};
pwm4{
label = "pwm4";
gpios = <&pio 6 12 GPIO_ACTIVE_HIGH>; //GPIO204 ----->PG12
};
};
2、驅動編寫
(1）解析dts檔案中的資料
static struct gpio_pwms_platform_data * gpio_pwms_get_devtree_pdata(struct device *dev)
{
struct device_node *node, *pp;
struct gpio_pwms_platform_data *pdata;
struct pwm_chip *pwm;
int error;
int npwms;
int i = 0;
node = dev->of_node;
if (!node)
return NULL;
npwms = of_get_child_count(node); //獲取dts檔案中pwm結點的個數
if (npwms == 0)
return NULL;
pdata = devm_kzalloc(dev, sizeof(*pdata) + npwms * (sizeof *pwm),GFP_KERNEL);
if (!pdata) {
error = -ENOMEM;
goto err_out;
}
pdata->pwms = (struct pwm_chip *)(pdata + 1);
pdata->npwms = npwms;
for_each_child_of_node(node, pp)
{
enum of_gpio_flags flags;
if (!of_find_property(pp, "gpios", NULL))
{
pdata->npwms--;
printk( "Found pwm without gpios\n");
continue;
}
pwm = &pdata->pwms[i++];
pwm->gpio = of_get_gpio_flags(pp, 0, &flags); //獲取每個pwm的gpio
printk("pwm->gpio=%d,flags=%d",pwm->gpio,flags);
if (pwm->gpio < 0)
{
error = pwm->gpio;
if (error != -ENOENT)
{
if (error != -EPROBE_DEFER)
dev_err(dev,
"Failed to get gpio flags, error: %d\n",
error);
return ERR_PTR(error);
}
}
else
{
pwm->active_low = flags ;
}
pwm->desc = of_get_property(pp, "label", NULL); //獲取label的字串
}
if (pdata->npwms == 0) {
error = -EINVAL;
goto err_out;
}
return pdata;
err_out:
return ERR_PTR(error);
}
（2）gpio_demo_probe函式主要用於建立pwm裝置和class，分別給四個pwm裝置分配主裝置和次裝置號,並且設定io口的輸入輸出。
static int gpio_demo_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
int error;
int i,ret=0;
unsigned int gpio;
struct pwm_chip *gpwm = NULL;
pdata = pdev->dev.platform_data;
if (!pdata) {
pdata = gpio_pwms_get_devtree_pdata(dev); //獲取dts中定義裝置樹的資料
if (IS_ERR(pdata))
return PTR_ERR(pdata);
if (!pdata) {
printk( "missing platform data\n");
return -EINVAL;
}
}
gloabl_pwms_dev = devm_kzalloc(dev, pdata->npwms * sizeof(struct pwm_chip),
GFP_KERNEL);
if (!gloabl_pwms_dev) {
printk("no memory for gloabl_pwms_dev data\n");
return -ENOMEM;
}
memcpy(gloabl_pwms_dev, pdata->pwms, pdata->npwms * sizeof(struct pwm_chip));
for(i=0;i<pdata->npwms;i++)
{
//申請主裝置和此裝置號,分配了cdev
註冊了字元裝置後，/dev/目錄下會生成pwm1\pwm2\pwm3\pwm4四個字元裝置。可以在應用層去對裝置進行讀寫操作，會呼叫到驅動下的這幾個函式。
const struct file_operations pwm_fops = {
.open = pwm_drv_open,
.write = pwm_drv_write,
.read = pwm_drv_read,
.unlocked_ioctl = pwm_drv_ioctl,
.release = pwm_drv_close,
};
（3）pwm_drv_ioctl函式會對應用層發過來的指令進行響應.
//command
#define PWM_PERIOD_SET _IOW('A', 1, unsigned long) #define PWM_DUTY_SET _IOW('A', 2, unsigned long) #define PWM_START _IOW('A', 3, unsigned long)
long pwm_drv_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
{
int ret = 0,minornum=0;
struct inode * ginode = NULL;
struct pwm_chip * pwm_dev = NULL;
ginode = file_inode(filep);
minornum= iminor(ginode);
pwm_dev = &gloabl_pwms_dev[minornum];
printk("pwm_drv_ioctl.minornum=%d...gpio=%d.period=%ld..duty=%ld..\n",minornum,pwm_dev->gpio,pwm_dev->period,pwm_dev->duty);
switch(minornum)
{
case 0:
pwm1_dev = &gloabl_pwms_dev[minornum];
break;
case 1:
pwm2_dev = &gloabl_pwms_dev[minornum];
break;
case 2:
pwm3_dev = &gloabl_pwms_dev[minornum];
break;
case 3:
pwm4_dev = &gloabl_pwms_dev[minornum];
break;
default:
break;
}
switch(cmd)
{
case PWM_PERIOD_SET :
if(0 == minornum)
{
pwm1_dev->period = arg;
}
else if(1 == minornum)
{
pwm2_dev->period = arg;
}
else if(2 == minornum)
{
pwm3_dev->period = arg;
}
else if(3 == minornum)
{
pwm4_dev->period = arg;
}
break;
case PWM_DUTY_SET :
if(0 == minornum)
{
pwm1_dev->duty = arg;
}
else if(1 == minornum)
{
pwm2_dev->duty = arg;
}
else if(2 == minornum)
{
pwm3_dev->duty = arg;
}
else if(3 == minornum)
{
pwm4_dev->duty = arg;
}
break;
case PWM_START :
if(0 == minornum)
{
if(pwm1_dev->status == PWM_DISABLE){
// start timer
pwm_gpio_start(minornum);
pwm1_dev->status = PWM_ENABLE;
}else{
printk("debug:pwm1_gpio aready work\n");
}
}
else if(1 == minornum)
{
if(pwm2_dev->status == PWM_DISABLE){
// start timer
pwm_gpio_start(minornum);
pwm2_dev->status = PWM_ENABLE;
}else{
printk("debug:pwm2_gpio aready work\n");
}
}
else if(2 == minornum)
{
if(pwm3_dev->status == PWM_DISABLE){
// start timer
pwm_gpio_start(minornum);
pwm3_dev->status = PWM_ENABLE;
}else{
printk("debug:pwm3_gpio aready work\n");
}
}
else if(3 == minornum)
{
if(pwm4_dev->status == PWM_DISABLE){
// start timer
pwm_gpio_start(minornum);
pwm4_dev->status = PWM_ENABLE;
}else{
printk("debug:pwm4_gpio aready work\n");
}
}
break;
default :
ret = -1;
break;
}
return 0;
}
(4)hrtimer精準定時器模擬pwm訊號
- 初始化定時器，是指hrtimer1_handler為回撥函式，hrtimer_start啟用回撥函式。
hrtimer_init(&pwm1_dev->mytimer,CLOCK_MONOTONIC,HRTIMER_MODE_REL); pwm1_dev->mytimer.function = hrtimer1_handler; pwm1_dev->kt = ktime_set(0, pwm1_dev->period-pwm1_dev->duty); hrtimer_start(&pwm1_dev->mytimer,pwm1_dev->kt,HRTIMER_MODE_REL);
- 初始化完之後會呼叫hrtimer1_handler函式，在回撥函式會判斷io口的電平高低，然後使用ktime_set設定到期時間，如果io為低電平，如果duty不為0，則拉高，ktime_set設定高電平的時間為duty,hrtimer_forward_now函式會等待duty納秒，然後再執行回撥函式hrtimer1_handler，再進行判斷，如此迴圈。使用hrtimer_cancel函式去取消hrtimer.
我們需要四個定時器去模擬pwm,故要寫四個回撥函式模擬。
注意：根據實際測量，這裡gpio_get_value獲取到gpio的值，1為低電平，0為高電平。
static enum hrtimer_restart hrtimer1_handler(struct hrtimer *timer)
{
if (gpio_get_value(pwm1_dev->gpio) == 1) {
// There is no need to pull down when the duty cycle is 100%
if (pwm1_dev->duty != 0) {
gpio_set_value(pwm1_dev->gpio, 0);
pwm1_dev->kt = ktime_set(0, pwm1_dev->duty);
}
// timer overflow
hrtimer_forward_now(&pwm1_dev->mytimer, pwm1_dev->kt);
} else {
// There is no need to pull up when the duty cycle is 0
if (pwm1_dev->duty != pwm1_dev->period) {
gpio_set_value(pwm1_dev->gpio, 1);
pwm1_dev->kt = ktime_set(0, pwm1_dev->period-pwm1_dev->duty);
}
// timer overflow
hrtimer_forward_now(&pwm1_dev->mytimer, pwm1_dev->kt);
}
return HRTIMER_RESTART;
}
（5）設備註冊
static struct of_device_id gpio_demo_of_match[] = {
{.compatible = "gpio-pwms"},
{},
}
MODULE_DEVICE_TABLE(of, gpio_demo_of_match);
static struct platform_driver gpio_demo_driver = {
.probe = gpio_demo_probe,
.driver = {
.name = "gpio-pwms",
.owner = THIS_MODULE,
.of_match_table = of_match_ptr(gpio_demo_of_match),
}
};
static int __init gpio_demo_init(void)
{
return platform_driver_register(&gpio_demo_driver);
}
static void __exit gpio_demo_exit(void)
{
int i;
struct pwm_chip *gpwm = NULL;
for(i=0;i<pdata->npwms;i++ )
{
gpwm = &gloabl_pwms_dev[i];
gpio_set_value(gpwm->gpio, 1);
gpio_free(gpwm->gpio);
device_destroy(pwm_class,gpwm->devno);
cdev_del(gpwm->cdev);
unregister_chrdev_region(gpwm->devno,1);
hrtimer_cancel(&gpwm->mytimer);
kfree(gpwm);
}
class_destroy(pwm_class);
return platform_driver_unregister(&gpio_demo_driver);
}
late_initcall(gpio_demo_init);
module_exit(gpio_demo_exit);
// add by SouthLj 2019-0924 end
MODULE_LICENSE("GPL");
MODULE_AUTHOR("SouthLj");
註冊完pwm裝置和gpio_pwms class就可以看到如下目錄：
可以看到裝置的主、次裝置號：
/dev目錄下也可以看到四個裝置，應用層就會通過ioctl對pwm裝置寫資料到驅動。
驅動的pwm_drv_ioctl函式根據應用層傳過來的指令設定pwm週期，duty資料調整pwm訊號。
luci介面中設定風扇的資料後，會將資料更新到/etc/config/cgminer配置檔案中，然後重新啟動cgminer(即執行/etc/init.d/cgminer指令碼)，指令碼中會將風扇風速最大最小值、風速預設值、風速自動控制、預啟動時間以及預啟動時間內風扇的風速，通過傳參傳給cgminer.
AVA9_OPTIONS=" --fan-limit $_fan_min-$_fan_max $VOLT_OFFSET"
PARAMS=" --lowmem $AVA9_OPTIONS $POOL1 $POOL2 $POOL3 --api-allow $_aa --api-listen $_mo --fan-ctrl $_fan_ctrl $PRE_BOOT --pwm-default $_pwm_default"
NTP_POOL="-p 0.openwrt.pool.ntp.org -p 1.openwrt.pool.ntp.org -p 3.openwrt.pool.ntp.org -p 4.openwrt.pool.ntp.org"
ASIA="-p 1.cn.pool.ntp.org -p 3.asia.pool.ntp.org -p 2.asia.pool.ntp.org"
# _ntp_enable: openwrt, asia, globle
if [ "$_ntp_enable" == "asia" ]; then
NTP_POOL="${ASIA}"
fi
if [ ! -f /tmp/cgminer-ntpd-done -a "$_ntp_enable" != "disable" ]; then
while [ "$NTPD_RET" != "0" ]; do
ntpd -d -n -q -N ${NTP_POOL}
NTPD_RET=$?
done
touch /tmp/cgminer-ntpd-done
fi
# Make sure udevd run before cgminer start
UDEVDCNT=`pidof udevd | wc -w`
if [ "$UDEVDCNT" == "0" ]; then
mkdir -p /run
udevd --daemon
fi
sleep 2
start-stop-daemon -S -x $APP -p $PID_FILE -m -b -- $PARAMS
pwm佔空比設到20%，pwm波形不穩定,導致風扇有頓挫感。nano給的軟體預設最小佔空比為30%.
cgminer.c中通過引數判斷會執行相應的函式：
char *set_avalon9_fan_auto_control(char *arg)
{
int ret=1,autocontrol=0;
ret = sscanf(arg, "%d", &autocontrol);
printf("autocontrol=%d\n",autocontrol);
if (ret < 1)
return "No value passed to avalon9-fan-auto-control";
opt_avalon9_fan_auto_control = autocontrol;
return NULL;
}
//風扇預啟動設定邏輯是，如果風扇自動控制開關為enable,控制板上電開機後，則會根據
預啟動速度跑，跑的時間是預啟動時間，時間過後，風扇風速會按照預設風速轉。預啟動
設定只在上電第一次有效。
char *set_avalon9_fan_pre_boot_setup(char *arg)
{
int ret=1,prebootime =1,prebootfan =100;
ret = sscanf(arg, "%d-%d", &prebootfan,&prebootime);
printf("prebootime=%d,prebootfan=%d\n",prebootime,prebootfan);
if (prebootfan < 0 || prebootfan> 100 || prebootime < 0 || prebootime > 10)
return "Invalid value passed to boot_setup";
if (ret < 1)
return "No value passed to avalon9-fan-pre-boot-setup";
prebootflag = 1;
opt_avalon9_fan_pre_boottim = prebootime;
opt_avalon9_fan_pre_bootfan = prebootfan;
return NULL;
}
void open_pwm_device(float pwmval)
{
int fd;
fd = open("/dev/pwm1",O_RDWR );
if(fd < 0)
{
printf("failed to open pwm1 failed!\n");
}
ioctl(fd,PWM_PERIOD_SET,40000); // 10 000 00ns = 1ms 10 00ns = 1us
ioctl(fd,PWM_DUTY_SET,(int)(40000*((float)pwmval/100)));
ioctl(fd,PWM_START,1);
close(fd);
fd = open("/dev/pwm2",O_RDWR);
if(fd < 0)
{
printf("failed to open pwm2!\n");
}
ioctl(fd,PWM_PERIOD_SET,40000); // 10 000 000ns = 10ms
ioctl(fd,PWM_DUTY_SET,(int)(40000*((float)pwmval/100)));
ioctl(fd,PWM_START,1);
close(fd);
fd = open("/dev/pwm3",O_RDWR);
if(fd < 0)
{
printf("failed to open pwm3 failed!\n");
}
ioctl(fd,PWM_PERIOD_SET,40000); // 10 000 000ns = 10ms
ioctl(fd,PWM_DUTY_SET,(int)(40000*((float)pwmval/100)));
ioctl(fd,PWM_START,1);
close(fd);
fd = open("/dev/pwm4",O_RDWR);
if(fd < 0)
{
printf("failed to open pwm4! \n");
}
ioctl(fd,PWM_PERIOD_SET,40000); // 10 000 000ns = 10ms
ioctl(fd,PWM_DUTY_SET,(int)(40000*((float)pwmval/100)));
ioctl(fd,PWM_START,1);
close(fd);
}
char *set_avalon9_fan_pwm_default(char *arg)
{
int pwmval;
int ret=1;
// int delaytime = 90000000;
ret = sscanf(arg, "%d", &pwmval);
printf("\n...........set_avalon9_fan_default_pwm....pwmval=%d..opt_avalon9_fan_auto_control=%d...\n",pwmval,opt_avalon9_fan_auto_control);
if (ret < 1)
return "No value passed to avalon9-fan-default-pwm";
if(pwmval<opt_avalon9_fan_min)
{
pwmval =opt_avalon9_fan_min;
}
else if(pwmval>opt_avalon9_fan_max)
{
pwmval =opt_avalon9_fan_max;
}
if(opt_avalon9_fan_auto_control == 1)
{
if(opt_avalon9_fan_pre_bootfan<opt_avalon9_fan_min)
{
opt_avalon9_fan_pre_bootfan =opt_avalon9_fan_min;
}
else if(opt_avalon9_fan_pre_bootfan>opt_avalon9_fan_max)
{
opt_avalon9_fan_pre_bootfan =opt_avalon9_fan_max;
}
if(prebootflag==1)
{
prebootflag==0;
open_pwm_device(opt_avalon9_fan_pre_bootfan);
cgsleep_ms(opt_avalon9_fan_pre_boottim*60000);
}
open_pwm_device(pwmval);
}
else
{
open_pwm_device(pwmval);
}
return NULL;
}
通過cat /sys/class/kernel/gpio命令檢視四個pwm口的電平高低。
static struct of_device_id gpio_demo_of_match[] = { {.compatible = "gpio-pwms"}, {},}MODULE_DEVICE_TABLE(of, gpio_demo_of_match);static struct platform_driver gpio_demo_driver = { .probe = gpio_demo_probe, .driver = {.name = "gpio-pwms",.owner = THIS_MODULE,.of_match_table = of_match_ptr(gpio_demo_of_match), }};static int __init gpio_demo_init(void){ return platform_driver_register(&gpio_demo_driver);}static void __exit gpio_demo_exit(void){int i; struct pwm_chip *gpwm = NULL;for(i=0;i<pdata->npwms;i++ ){gpwm = &gloabl_pwms_dev[i];gpio_set_value(gpwm->gpio, 1);gpio_free(gpwm->gpio);device_destroy(pwm_class,gpwm->devno);cdev_del(gpwm->cdev);unregister_chrdev_region(gpwm->devno,1);hrtimer_cancel(&gpwm->mytimer);kfree(gpwm);}class_destroy(pwm_class); return platform_driver_unregister(&gpio_demo_driver);}late_initcall(gpio_demo_init);module_exit(gpio_demo_exit);// add by SouthLj 2019-0924 endMODULE_LICENSE("GPL");MODULE_AUTHOR("SouthLj");