Uboot adds hardware watchdog

Let's talk about it first. uboot Compilation process ：

1.make distclean

2.make defconfig

3. make

Before executing the above , It is also necessary Set up , Such as configuration ARCH CROSS_COMPILE_ wait , Configure this environment variable in embedded development , To form a conditioned reflex . Then you can run the above 3 Step ：

1. eliminate , 

2. To configure , This needs to be explained in detail , This step is based on configs/defconfig file , To do some basic configuration , And generate include/config.h The header file .

3. make This is the real compilation

Actually uboot Framework Hardware watchdog is supported in ,

In the series configuration file configs/mx6qsabreauto.h, Definition CONFIG_HW_WATCHDOG

Then realize the following 2 A function , this 2 A function stay watchdog.h Statement in , seeing the name of a thing one thinks of its function , One is initialization , One is to feed the dog ,

void hw_watchdog_init(void);

void hw_watchdog_reset(void);

feed a dog hw_watchdog_reset, stay uboot The frequency of calls in is very high , Don't try to add print information to it , Once you add printf, Will crash .

stay uboot Add watchdog in , In fact, it is not complicated , But my watchdog chip uses MAX6323, This chip is my first 1 Secondary use , It's different from the watchdog I used before , The watchdog I used before DS1832, Just keep feeding the dog , There would be no reset , But this MAX6323, Quite abnormal , Hey, it's not good even if it's fast , You can't feed too slowly , It must be neither fast nor slow , Here's the picture ：

This is more troublesome , If in Uboot Pig feeding function provided hw_watchdog_reset（） in , If you change the level directly , It will be less than FAST Value of mode , Cause the dog to be fed too fast and reset , So we must control the time of feeding dogs 15ms<t<10s, Only in this way can we satisfy MAX6323 The requirements of .

On the key code , explain ： Feeding the dog uses the inside of the chip get_ticks(); Initializing ticks after , The value obtained by this function will always increase , Therefore, this value can be used to make a count , When this count is met , Will be in hw_watchdog_reset（） Change the level in ,

void hw_watchdog_reset(void)

{

    static int sta =1;

    static unsigned long long tim_bak = 0;

    unsigned long long ticks = get_ticks();

    if(ticks > tim_bak) {

        if((ticks-tim_bak) > 1000000)

        {

            tim_bak = ticks;

            if(sta){

                sta = 0;                

            }

            else{

                sta = 1;

            }

            gpio_direction_output(IMX_GPIO_NR(4, 30), sta);

        }

    }

}