From 5a3f22617b02ec366461be21765e636e6bdd0222 Mon Sep 17 00:00:00 2001
From: inmarket <andrewh@inmarket.com.au>
Date: Mon, 6 Oct 2014 17:05:16 +1000
Subject: Add support for FreeRTOS into make system

---
 boards/base/RaspberryPi/FreeRTOS/startup.s | 102 +++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)
 create mode 100644 boards/base/RaspberryPi/FreeRTOS/startup.s

(limited to 'boards/base/RaspberryPi/FreeRTOS/startup.s')

diff --git a/boards/base/RaspberryPi/FreeRTOS/startup.s b/boards/base/RaspberryPi/FreeRTOS/startup.s
new file mode 100644
index 00000000..d865439f
--- /dev/null
+++ b/boards/base/RaspberryPi/FreeRTOS/startup.s
@@ -0,0 +1,102 @@
+.extern	system_init
+.extern __bss_start
+.extern __bss_end
+.extern vFreeRTOS_ISR
+.extern vPortYieldProcessor
+.extern DisableInterrupts
+.extern FreeRTOS_Main
+	.section .init
+	.globl _start
+;; 
+_start:
+	;@ All the following instruction should be read as:
+	;@ Load the address at symbol into the program counter.
+	
+	ldr	pc,reset_handler		;@ 	Processor Reset handler 		-- we will have to force this on the raspi!
+	;@ Because this is the first instruction executed, of cause it causes an immediate branch into reset!
+	
+	ldr pc,undefined_handler	;@ 	Undefined instruction handler 	-- processors that don't have thumb can emulate thumb!
+    ldr pc,swi_handler			;@ 	Software interrupt / TRAP (SVC) -- system SVC handler for switching to kernel mode.
+    ldr pc,prefetch_handler		;@ 	Prefetch/abort handler.
+    ldr pc,data_handler			;@ 	Data abort handler/
+    ldr pc,unused_handler		;@ 	-- Historical from 26-bit addressing ARMs -- was invalid address handler.
+    ldr pc,irq_handler			;@ 	IRQ handler
+    ldr pc,fiq_handler			;@ 	Fast interrupt handler.
+
+	;@ Here we create an exception address table! This means that reset/hang/irq can be absolute addresses
+reset_handler:      .word reset
+undefined_handler:  .word undefined_instruction
+swi_handler:        .word vPortYieldProcessor
+prefetch_handler:   .word prefetch_abort
+data_handler:       .word data_abort
+unused_handler:     .word unused
+irq_handler:        .word vFreeRTOS_ISR
+fiq_handler:        .word fiq
+
+reset:
+	;@	In the reset handler, we need to copy our interrupt vector table to 0x0000, its currently at 0x8000
+
+	mov r0,#0x8000								;@ Store the source pointer
+    mov r1,#0x0000								;@ Store the destination pointer.
+
+	;@	Here we copy the branching instructions
+    ldmia r0!,{r2,r3,r4,r5,r6,r7,r8,r9}			;@ Load multiple values from indexed address. 		; Auto-increment R0
+    stmia r1!,{r2,r3,r4,r5,r6,r7,r8,r9}			;@ Store multiple values from the indexed address.	; Auto-increment R1
+
+	;@	So the branches get the correct address we also need to copy our vector table!
+    ldmia r0!,{r2,r3,r4,r5,r6,r7,r8,r9}			;@ Load from 4*n of regs (8) as R0 is now incremented.
+    stmia r1!,{r2,r3,r4,r5,r6,r7,r8,r9}			;@ Store this extra set of data.
+
+
+	;@	Set up the various STACK pointers for different CPU modes
+    ;@ (PSR_IRQ_MODE|PSR_FIQ_DIS|PSR_IRQ_DIS)
+    mov r0,#0xD2
+    msr cpsr_c,r0
+    mov sp,#0x8000
+
+    ;@ (PSR_FIQ_MODE|PSR_FIQ_DIS|PSR_IRQ_DIS)
+    mov r0,#0xD1
+    msr cpsr_c,r0
+    mov sp,#0x4000
+
+    ;@ (PSR_SVC_MODE|PSR_FIQ_DIS|PSR_IRQ_DIS)
+    mov r0,#0xD3
+    msr cpsr_c,r0
+	mov sp,#0x8000000
+
+	ldr r0, =__bss_start
+	ldr r1, =__bss_end
+
+	mov r2, #0
+
+zero_loop:
+	cmp 	r0,r1
+	it		lt
+	strlt	r2,[r0], #4
+	blt		zero_loop
+
+	bl 		DisableInterrupts
+	
+	
+	;@ 	mov	sp,#0x1000000
+	b FreeRTOS_Main									;@ We're ready?? Lets start main execution!
+	.section .text
+
+undefined_instruction:
+	b undefined_instruction
+
+prefetch_abort:
+	b prefetch_abort
+
+data_abort:
+	b data_abort
+
+unused:
+	b unused
+
+fiq:
+	b fiq
+	
+hang:
+	b hang
+
-- 
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