forked from Imagelibrary/rtems
511dc4b2be
Statically initialize the interrupt stack area
(_Configuration_Interrupt_stack_area_begin,
_Configuration_Interrupt_stack_area_end, and
_Configuration_Interrupt_stack_size) via <rtems/confdefs.h>. Place the
interrupt stack area in a special section ".rtemsstack.interrupt". Let
BSPs define the optimal placement of this section in their linker
command files (e.g. in a fast on-chip memory).
This change makes makes the CPU_HAS_SOFTWARE_INTERRUPT_STACK and
CPU_HAS_HARDWARE_INTERRUPT_STACK CPU port defines superfluous, since the
low level initialization code has all information available via global
symbols.
This change makes the CPU_ALLOCATE_INTERRUPT_STACK CPU port define
superfluous, since the interrupt stacks are allocated by confdefs.h for
all architectures. There is no need for BSP-specific linker command
file magic (except the section placement), see previous ARM linker
command file as a bad example.
Remove _CPU_Install_interrupt_stack(). Initialize the hardware
interrupt stack in _CPU_Initialize() if necessary (e.g.
m68k_install_interrupt_stack()).
The optional _CPU_Interrupt_stack_setup() is still useful to customize
the registration of the interrupt stack area in the per-CPU information.
The initialization stack can reuse the interrupt stack, since
* interrupts are disabled during the sequential system initialization,
and
* the boot_card() function does not return.
This stack resuse saves memory.
Changes per architecture:
arm:
* Mostly replace the linker symbol based configuration of stacks with
the standard <rtems/confdefs.h> configuration via
CONFIGURE_INTERRUPT_STACK_SIZE. The size of the FIQ, ABT and UND
mode stack is still defined via linker symbols. These modes are
rarely used in applications and the default values provided by the
BSP should be sufficient in most cases.
* Remove the bsp_processor_count linker symbol hack used for the SMP
support. This is possible since the interrupt stack area is now
allocated by the linker and not allocated from the heap. This makes
some configure.ac stuff obsolete. Remove the now superfluous BSP
variants altcycv_devkit_smp and realview_pbx_a9_qemu_smp.
bfin:
* Remove unused magic linker command file allocation of initialization
stack. Maybe a previous linker command file copy and paste problem?
In the start.S the initialization stack is set to a hard coded value.
lm32, m32c, mips, nios2, riscv, sh, v850:
* Remove magic linker command file allocation of initialization stack.
Reuse interrupt stack for initialization stack.
m68k:
* Remove magic linker command file allocation of initialization stack.
Reuse interrupt stack for initialization stack.
powerpc:
* Remove magic linker command file allocation of initialization stack.
Reuse interrupt stack for initialization stack.
* Used dedicated memory region (REGION_RTEMSSTACK) for the interrupt
stack on BSPs using the shared linkcmds.base (replacement for
REGION_RWEXTRA).
sparc:
* Remove the hard coded initialization stack. Use the interrupt stack
for the initialization stack on the boot processor. This saves
16KiB of RAM.
Update #3459.
BSP for the Raspberry Pi ARM board
This is a basic port that should work on either Model A or Model B.
It currently supports the following devices:
o Console using the PL011 UART0
The console driver only works with polled mode right now,
the interrupt code is there, but it does not work yet.
The console driver is currently hardcoded at 115k 8N1
o Clock uses the internal ARM timer
The Raspberry Pi can be overclocked through the config.txt file, this
would affect the duration of the clock tick.
o Benchmark timer reads the lower 32 bit GPU timer register
To run an RTEMS binary, it must be stripped and loaded on the SD card along with
the following files:
bootcode.bin
config.txt
loader.bin
start.elf
kernel.img ( the RTEMS binary, you can change the name in config.txt )
These files can be obtained from a Linux installation image, or from here:
https://github.com/raspberrypi/firmware
I used an old 256MB SD card to boot RTEMS.
Much more information about the SD card file and bootloader can be found here:
http://elinux.org/RPi_Hub
http://www.raspberrypi.org
The linker script is set up for 128MB, so it can be used with a GPU/ARM split
of 128/128.
The bootloader that is used on the SD card determines the split of RAM between the
ARM and the GPU. It might make sense to adjust the GPU/ARM memory split to give
more memory to RTEMS, especially on a 512MB board.
To do:
It would be nice to get support in the BSP for the following:
o SD card
o USB and USB 10/100 network chip on Model B
o SPI
o GPIO
o ARM MMU
o Graphics console
o Sound
Credits and links:
There is a wealth of code and information to reference on the raspberrypi.org bare metal forums:
http://www.raspberrypi.org/phpBB3/viewforum.php?f=72
I found information about how to program the timers, interrupts, and UART 0
from the examples provided by:
David Welch:
https://github.com/dwelch67/raspberrypi
The readme file at his github repository has valuable information about connecting a UART cable, JTAG etc.
Steve Bate:
http://www.stevebate.net/chibios-rpi/GettingStarted.html
Steve provided a port of the Chibios RTOS to the raspberry Pi
James Walmsley:
http://www.raspberrypi.org/phpBB3/viewtopic.php?f=72&t=22423
James ported FreeRTOS to the raspberry Pi.