GPIO debounce on IMX8MP

growbook — Fri, 30 Jun 2023 06:57:32 GMT

Hello,

I'm trying to set GPIO debounce time on Linux made from Yocto.

I was going to do it using gpio_set_debounce() function.

Like this :

if(gpio_set_debounce(GPIO_25_IN, 200) < 0){

pr_err("ERROR: gpio_set_debounce - %d\n", GPIO_25_IN);

}

However, it always makes an error.

Is it possible to enable GPIO debounce? or Is there any pre-defined debounce time?

regards

growbook

Re: GPIO debounce on IMX8MP

Dhruvit — Mon, 03 Jul 2023 12:31:22 GMT

Hi @growbook,

I hope you are doing well.

Please share the dmesg logs or error logs also to debug the issue further.

Thanks & Regards,
Dhruvit Vasavada

Re: GPIO debounce on IMX8MP

growbook — Tue, 04 Jul 2023 05:43:35 GMT

Sorry that I've offered a few clues for debugging.

This is my code.

(You may not need to read the whole code. I'll explain it in the next paragraph)

/***************************************************************************//** * \file driver.c * * \details Simple GPIO driver explanation (GPIO Interrupt) * * \author EmbeTronicX * * \Tested with Linux raspberrypi 5.4.51-v7l+ * *******************************************************************************/ #include <linux/kernel.h> #include <linux/init.h> #include <linux/module.h> #include <linux/kdev_t.h> #include <linux/fs.h> #include <linux/cdev.h> #include <linux/device.h> #include <linux/delay.h> #include <linux/uaccess.h> //copy_to/from_user() #include <linux/gpio.h> //GPIO #include <linux/interrupt.h> #include <linux/err.h> /* Since debounce is not supported in Raspberry pi, I have addded this to disable ** the false detection (multiple IRQ trigger for one interrupt). ** Many other hardware supports GPIO debounce, I don't want care about this even ** if this has any overhead. Our intention is to explain the GPIO interrupt. ** If you want to disable this extra coding, you can comment the below macro. ** This has been taken from : https://raspberrypi.stackexchange.com/questions/8544/gpio-interrupt-debounce ** ** If you want to use Hardaware Debounce, then comment this EN_DEBOUNCE. ** */ // #define EN_DEBOUNCE #ifdef EN_DEBOUNCE #include <linux/jiffies.h> extern unsigned long volatile jiffies; unsigned long old_jiffie = 0; #endif //LED is connected to this GPIO #define GPIO_137_OUT 137 //LED is connected to this GPIO #define GPIO_135_IN 135 //GPIO_135_IN value toggle unsigned int led_toggle = 0; //This used for storing the IRQ number for the GPIO unsigned int GPIO_irqNumber; //Interrupt handler for GPIO 135. This will be called whenever there is a raising edge detected. static irqreturn_t gpio_irq_handler(int irq,void *dev_id) { static unsigned long flags = 0; #ifdef EN_DEBOUNCE unsigned long diff = jiffies - old_jiffie; pr_info("diff calculation is called"); if (diff < 20) { return IRQ_HANDLED; } old_jiffie = jiffies; #endif local_irq_save(flags); led_toggle = (0x01 ^ led_toggle); // toggle the old value gpio_set_value(GPIO_137_OUT, led_toggle); // toggle the GPIO_137_OUT pr_info("Interrupt Occurred : GPIO_137_OUT : %d ",gpio_get_value(GPIO_137_OUT)); local_irq_restore(flags); return IRQ_HANDLED; } dev_t dev = 0; static struct class *dev_class; static struct cdev etx_cdev; static int __init etx_driver_init(void); static void __exit etx_driver_exit(void); /*************** Driver functions **********************/ static int etx_open(struct inode *inode, struct file *file); static int etx_release(struct inode *inode, struct file *file); static ssize_t etx_read(struct file *filp, char __user *buf, size_t len,loff_t * off); static ssize_t etx_write(struct file *filp, const char *buf, size_t len, loff_t * off); /******************************************************/ //File operation structure static struct file_operations fops = { .owner = THIS_MODULE, .read = etx_read, .write = etx_write, .open = etx_open, .release = etx_release, }; /* ** This function will be called when we open the Device file */ static int etx_open(struct inode *inode, struct file *file) { pr_info("Device File Opened...!!!\n"); return 0; } /* ** This function will be called when we close the Device file */ static int etx_release(struct inode *inode, struct file *file) { pr_info("Device File Closed...!!!\n"); return 0; } /* ** This function will be called when we read the Device file */ static ssize_t etx_read(struct file *filp, char __user *buf, size_t len, loff_t *off) { uint8_t gpio_state = 0; //reading GPIO value gpio_state = gpio_get_value(GPIO_137_OUT); //write to user len = 1; if( copy_to_user(buf, &gpio_state, len) > 0) { pr_err("ERROR: Not all the bytes have been copied to user\n"); } pr_info("Read function : GPIO_137 = %d \n", gpio_state); pr_info("Read function : GPIO_135 = %d \n", gpio_get_value(GPIO_135_IN)); return 0; } /* ** This function will be called when we write the Device file */ static ssize_t etx_write(struct file *filp, const char __user *buf, size_t len, loff_t *off) { uint8_t rec_buf[10] = {0}; if( copy_from_user( rec_buf, buf, len ) > 0) { pr_err("ERROR: Not all the bytes have been copied from user\n"); } if (rec_buf[0]=='1') { //set the GPIO value to HIGH gpio_set_value(GPIO_137_OUT, 1); } else if (rec_buf[0]=='0') { //set the GPIO value to LOW gpio_set_value(GPIO_137_OUT, 0); } else { pr_err("Unknown command : Please provide either 1 or 0 \n"); } pr_info("Write Function : GPIO_137 Set = %c\n", rec_buf[0]); return len; } /* ** Module Init function */ static int __init etx_driver_init(void) { /*Allocating Major number*/ if((alloc_chrdev_region(&dev, 0, 1, "etx_Dev")) <0){ pr_err("Cannot allocate major number\n"); goto r_unreg; } pr_info("Major = %d Minor = %d \n",MAJOR(dev), MINOR(dev)); /*Creating cdev structure*/ cdev_init(&etx_cdev,&fops); /*Adding character device to the system*/ if((cdev_add(&etx_cdev,dev,1)) < 0){ pr_err("Cannot add the device to the system\n"); goto r_del; } /*Creating struct class*/ if(IS_ERR(dev_class = class_create(THIS_MODULE,"etx_class"))){ pr_err("Cannot create the struct class\n"); goto r_class; } /*Creating device*/ if(IS_ERR(device_create(dev_class,NULL,dev,NULL,"etx_device"))){ pr_err( "Cannot create the Device \n"); goto r_device; } //Output GPIO configuration //Checking the GPIO is valid or not if(gpio_is_valid(GPIO_137_OUT) == false){ pr_err("GPIO %d is not valid\n", GPIO_137_OUT); goto r_device; } //Requesting the GPIO if(gpio_request(GPIO_137_OUT,"GPIO_137_OUT") < 0){ pr_err("ERROR: GPIO %d request\n", GPIO_137_OUT); goto r_gpio_out; } //configure the GPIO as output gpio_direction_output(GPIO_137_OUT, 0); //Input GPIO configuratioin //Checking the GPIO is valid or not if(gpio_is_valid(GPIO_135_IN) == false){ pr_err("GPIO %d is not valid\n", GPIO_135_IN); goto r_gpio_in; } //Requesting the GPIO if(gpio_request(GPIO_135_IN,"GPIO_135_IN") < 0){ pr_err("ERROR: GPIO %d request\n", GPIO_135_IN); goto r_gpio_in; } //configure the GPIO as input gpio_direction_input(GPIO_135_IN); /* ** I have commented the below few lines, as gpio_set_debounce is not supported ** in the Raspberry pi. So we are using EN_DEBOUNCE to handle this in this driver. */ #ifndef EN_DEBOUNCE //Debounce the button with a delay of 200ms pr_info("gpio_set_debounce is called\n"); if(gpio_set_debounce(GPIO_135_IN, 1000) < 0){ pr_err("ERROR: gpio_set_debounce - %d\n", GPIO_135_IN); //goto r_gpio_in; } #endif //Get the IRQ number for our GPIO GPIO_irqNumber = gpio_to_irq(GPIO_135_IN); pr_info("GPIO_irqNumber = %d\n", GPIO_irqNumber); if (request_irq(GPIO_irqNumber, //IRQ number (void *)gpio_irq_handler, //IRQ handler IRQF_TRIGGER_RISING, //Handler will be called in raising edge "etx_device", //used to identify the device name using this IRQ NULL)) { //device id for shared IRQ pr_err("my_device: cannot register IRQ "); goto r_gpio_in; } pr_info("Device Driver Insert...Done!!!\n"); return 0; r_gpio_in: gpio_free(GPIO_135_IN); r_gpio_out: gpio_free(GPIO_137_OUT); r_device: device_destroy(dev_class,dev); r_class: class_destroy(dev_class); r_del: cdev_del(&etx_cdev); r_unreg: unregister_chrdev_region(dev,1); return -1; } /* ** Module exit function */ static void __exit etx_driver_exit(void) { free_irq(GPIO_irqNumber,NULL); gpio_free(GPIO_135_IN); gpio_free(GPIO_137_OUT); device_destroy(dev_class,dev); class_destroy(dev_class); cdev_del(&etx_cdev); unregister_chrdev_region(dev, 1); pr_info("Device Driver Remove...Done!!\n"); } module_init(etx_driver_init); module_exit(etx_driver_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("EmbeTronicX <embetronicx@gmail.com>"); MODULE_DESCRIPTION("A simple device driver - GPIO Driver (GPIO Interrupt) "); MODULE_VERSION("1.33");

This code is a simple GPIO driver for handling interrupts on a Linux system. Although comments in the code seem like targeting the Raspberry Pi platform, I've tested it on Imx8mp board. It allows users to control an output GPIO (GPIO_137) and receive interrupt notifications when a rising edge is detected on an input GPIO (GPIO_135).

The functionality I want to implement is setting debounce time. I've tried to search 'debounce' on every datasheet of imx8mp, but I could not find it. So, I was wondering that Imx8mp support debounce time or not.

Also, Here is dmesg.

[ 124.721829] gpio_irq: loading out-of-tree module taints kernel. [ 124.728804] Major = 510 Minor = 0 [ 124.732897] gpio_set_debounce is called [ 124.736778] ERROR: gpio_set_debounce - 135 [ 124.740951] GPIO_irqNumber = 224 [ 124.744225] Device Driver Insert...Done!!!

This is a message when the device driver module started.

At the fourth line, gpio_set_debounce returns an error.

So, now I'm trying to set the debounce time at device tree like this.

gpio-keys { compatible = "gpio-keys"; pinctrl-names = "default"; pinctrl-0 = <&pinctrl_gpio_switch>; switch { label = "button"; gpios = <&gpio5 7 GPIO_ACTIVE_HIGH>; debounce-interval = <100>; }; }; (emitted) pinctrl_gpio_switch: gpioswitchgrp { fsl,pins = < MX8MP_IOMUXC_ECSPI1_MOSI__GPIO5_IO07 0x16 >; };

And it also doesn't work as I expected.

Thank you for your reply.

Best regards,

growbook91

Re: GPIO debounce on IMX8MP

Dhruvit — Wed, 05 Jul 2023 08:40:55 GMT

Hi @growbook,

I hope you are doing well.

->Thanks for sharing the code & further details.

->Please check with the pad settings you made in the code are being used by other nodes or not in the same device tree.
->I found out that uart3 also uses the same pad so please disable the uart3 node from the device tree by doing the below settings.
status = "disabled"

Now it should work.

Thanks & Regards,
Dhruvit Vasavada

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