Kernel-porting[Beaglebone]

board_am335xevm.c

File Name: am335x_evm_board.c



+MACHINE_START(AM335XEVM, "am335xevm")
+        /* Maintainer: Texas Instruments */
+        .atag_offset    = 0x100,
+        .map_io         = am335x_evm_map_io,
+        .init_early     = am33xx_init_early,
+        .init_irq       = ti81xx_init_irq,
+        .handle_irq     = omap3_intc_handle_irq,
+        .timer          = &omap3_am33xx_timer,
+        .init_machine   = am335x_evm_init,
+MACHINE_END


->The Machine Start Macro is used to indentify
	initialization functions to the Linux kernel


+        .atag_offset    = 0x100,  

->Boot parameter location passed form u-boot


+        .map_io         = am335x_evm_map_io

static void __init am335x_evm_map_io(void)
{
        omap2_set_globals_am33xx();
        omapam33xx_map_common_io();
}


-> omapam33xx_map_common_io() is called from arch/arm/mach-omap2/common.c



+        .init_early     = am33xx_init_early,

->The am33xx_init_early is a function within
	the OMAP2+ Shared common code
	
-> This is called directly from the common code
	without modification
	
 .init_irq       = ti81xx_init_irq,
 
-> arch/arm/mach-omap2/irq.c
ti81xx_init_irq()
	Interrupt initilization function
	
	

.handle_irq     = omap3_intc_handle_irq
	
-> arch/arm/mach-omap2/irq.c
	omap3_intc_handle_irq()
Interrupt handler function regration with the kernel.



.timer          = &omap3_am33xx_timer,
-> arch/arm/mach-omap2/timer.c
omap3_am33xx_timer()
{
...
....
}
 system timer definition.
 
 

.init_machine   = am335x_evm_init,

-> arch/arm/mach-omap2/board-am335xevm.c

static void __init am335x_evm_init(void)
{
        am33xx_cpuidle_init();
        am33xx_mux_init(board_mux);
        omap_serial_init();
        am335x_evm_i2c_init();
        omap_sdrc_init(NULL, NULL);
        usb_musb_init(&musb_board_data);
        omap_board_config = am335x_evm_config;
        omap_board_config_size = ARRAY_SIZE(am335x_evm_config);
        /* Create an alias for icss clock */
        if (clk_add_alias("pruss", NULL, "pruss_uart_gclk", NULL))
                pr_warn("failed to create an alias: icss_uart_gclk --> pruss\n");
        /* Create an alias for gfx/sgx clock */
        if (clk_add_alias("sgx_ck", NULL, "gfx_fclk", NULL))
                pr_warn("failed to create an alias: gfx_fclk --> sgx_ck\n");
}


-> am33xx_cpuidle_init();
        am33xx_mux_init(board_mux);
        omap_serial_init();
        Above threee functions are from "arch/arm/mach-omap2/cpuidle33xx.c"
        			[Loads cpu idle driver for AM33xx]
        				"arch/arm/mach-omap2/mux.c"
        			[Intilizes omap pin mux abstraction]	
        				"arch/arm/mach-omap2/serial.c" 
        		[Enables UARTs configured for the omap platforms, 
        		set up pin mux and clock]