Uboot reads the DDR memory size by sending 'R' characters through the terminal

uboot Send through the terminal ’r’ Character reading ddr Memory size

static int show_dram(void)
{
    
	unsigned long long size;

#ifdef CONFIG_NR_DRAM_BANKS
	int i;

	debug("\nRAM Configuration:\n");
	for (i = size = 0; i < CONFIG_NR_DRAM_BANKS; i++) {
    
		size += gd->bd->bi_dram[i].size;
		debug("Bank #%d: %llx ", i,
		      (unsigned long long)(gd->bd->bi_dram[i].start));
#ifdef DEBUG
		print_size(gd->bd->bi_dram[i].size, "\n");
#endif
	}
	debug("\nDRAM: ");
#else
	size = gd->ram_size;
#endif

	print_size(size, "");
	putc('\n');

	return 0;
}

static int run_main_loop(void)
{
    
int flag=1;
#ifdef CONFIG_SANDBOX
	sandbox_main_loop_init();
#endif
	/* main_loop() can return to retry autoboot, if so just run it again */
	for (;;){
    
		if (flag&&serial_getc() == 'r'){
    
		show_dram();
		flag=~flag;
		}
	}	
	main_loop();
	return 0;
}