Rtems 4.11 Start-up process (arm, Beagle)

Please refer to the official BSP_HOWTO documentation, for ARM, the first file to execute is start. S

Start. S

C/src/lib/libbsp/arm/shared/start/start. S

1, from the _start start execution
2, off the CPU interrupt, initialize the register, set the stack of each mode, call Bsp_start_hook_0 (), note: At this time the exception vector table is not configured
3. Then copy the vector to the real position (but not set CP15)
4. Call Bsp_start_hook_1 ()
5, Last Call Boot_card (), this function should not return, if unfortunate return, will call Bsp_reset () restart

According to the BSP_HOWTO documentation, the things you should do before calling Boot_card () are as follows:
1. Init stack
2, zero. BSS
3. Disable IRQ
4. Copy. Data to RAM
Among them, items 2nd and 4 are not at start. s, where are they? Let's take a look at Beagle's bsp_start_hook_0 () and Bsp_start_hook_1 (), which are

C/SRC/LIB/LIBBSP/ARM/BEAGLE/STARTUP/BSPSTARTHOOKS.C

Bsp_start_hook_0() didn't do anything.

Bsp_start_hook_1()
Arm_a8core_start_hook_1 () =c/src/lib/libbsp/arm/include/arm-a8core-start.hTell Cp15 where the interrupt vector is.
Bsp_start_copy_sections () =c/src/lib/libbsp/arm/include/start.hCopy standard sections to memory, including. Data to initialize to memory
Beagle_setup_mmu_and_cache () =c/src/lib/libbsp/arm/beagle/startup/bspstartmmu.cSet up the MMU of the board
BSP_START_CLEAR_BSS () =c/src/lib/libbsp/arm/include/start.hClear 0. BSS segment

All the tasks before Boot_card () in Bsp_howto have been completed, then take a look at Boot_card ()

Boot_card ()

The default implementation of Boot_card () is c/src/lib/libbsp/shared/bootcard.c, and the implementation is simple:
1. Off interrupt
2. Log the command line (if Bootloader is uboot, there may be a command line)
3, call Rtems_initialize_executive () into the core of the Rtems zone ~

Rtems_initialize_executive () in cpukit/sapi/src/exinit.c
Call all registered Rtems_sysinit_item (initializers) once, and then the operating system officially starts running

Where does Rtems_sysinit_item come from? Speaking here we also have to think about the BSP_HOWTO manual in the said Bsp_work_area_initialize/bsp_start/bsp_predriver_hook where, look back to BOOTCARD.C bar, in Boot_card ( ) above the function, there are also these definitions

Rtems_sysinit_item (  bsp_work_area_initialize,  rtems_sysinit_bsp_work_areas,  rtems_sysinit_order_ Middle); Rtems_sysinit_item (  Bsp_start,  Rtems_sysinit_bsp_start,  rtems_sysinit_order_middle); Rtems_sysinit_item (  Bsp_predriver_hook,  rtems_sysinit_bsp_pre_drivers,  

That's what Rtems_sysinit_item defines! So what's the order of them, and see if cpukit/score/include/rtems/sysinit.h is probably in the order of the definition, and how to do it in the order of definition, I don't know now, dig a hole first.

Bsp_work_area_initialize () in c/src/lib/libbsp/shared/bspgetworkarea.c, the default implementation is generally used
Bsp_start () in c/src/lib/libbsp/arm/beagle/startup/bspstart.c call bsp_interrupt_initialize () = Bsp_ Interrupt_facility_initialize () Initialize the interrupt controller (as described in the Bsp_howto Manual) (in c/src/lib/libbsp/arm/beagle/irq.c )
Bsp_predriver_hook () default implementation nothing is done in c/src/lib/libbsp/shared/bsppredriverhook.c .

Other

Bsp_reset () The main function in c/src/lib/libbsp/arm/beagle/startup/bspreset.c is to restart the system.

Beagle_setup_mmu_and_cache () initializes the MMU, initializes the MMU based on the section configuration table, and the table is mostly armv7_cp15_start_default_sections, defined in c/src/ The Lib/libbsp/arm/shared/include/arm-cp15-start.h !

At this point, the initialization steps of the Rtems operating system are generally clear ^_^

Rtems 4.11 Start-up process (arm, Beagle)