From 830531b7d463155018857ca9899e760d72208279 Mon Sep 17 00:00:00 2001
From: Michael Sevakis <jethead71@rockbox.org>
Date: Fri, 14 Oct 2011 00:01:41 +0000
Subject: i.MX31: Simplify nested interrupt handling. Give SVC mode its own
 stack by grabbing the FIQ stack that's just been taking up space. Just get
 rid of all FIQ setup since it isn't used anyway.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@30747 a1c6a512-1295-4272-9138-f99709370657
---
 firmware/target/arm/imx31/crt0.S | 35 ++++++++++++++++++-----------------
 1 file changed, 18 insertions(+), 17 deletions(-)

(limited to 'firmware/target/arm/imx31/crt0.S')

diff --git a/firmware/target/arm/imx31/crt0.S b/firmware/target/arm/imx31/crt0.S
index 69577e4d3d..b6a49266ef 100644
--- a/firmware/target/arm/imx31/crt0.S
+++ b/firmware/target/arm/imx31/crt0.S
@@ -32,8 +32,9 @@ start:
     b       prefetch_abort_handler
     b       data_abort_handler
     b       reserved_handler
+    /* These vectors are unused */
     subs    pc, lr, #4              @ b       irq_handler
-    b       fiq_handler
+    subs    pc, lr, #4              @ b       fiq_handler
     .balign 0x40, 0x6B
 
 /* Arm bootloader and startup code based on startup.s from the iPodLinux loader
@@ -80,7 +81,7 @@ remap_start:
     mcrne   p15, 0, r0, c7, c7, 0  /* invalidate I cache and D cache */
     mcr     p15, 0, r0, c8, c7, 0  /* invalidate TLBs */
     mcr     p15, 0, r0, c7, c10, 4 /* Drain the write buffer */
-    
+
     mcr     p15, 0, r0, c13, c0, 0
     mcr     p15, 0, r0, c13, c0, 1
 
@@ -100,7 +101,7 @@ remap_start:
     bic     r3, r3, #((1 << 2) |  /* L1 D-cache disabled */ \
                       (1 << 0))   /* MMU disabled */
     mcr     p15, 0, r3, c1, c0, 0
-    
+
     /*
      * Configure L2 Cache:
      * - 128k size(16k way)
@@ -175,7 +176,7 @@ remap_start:
     mov     r0, #0
     mcr     p15, 0, r0, c8, c7, 0 /* Invalidate TLB */
     mcr     p15, 0, r0, c7, c7, 0 /* Invalidate icache and dcache */
-    
+
     /* Auxilliary control register */
     mrc     p15, 0, r0, c1, c0, 1
     bic     r0, r0, #((1 << 6) | /* Restrict cache size OFF */ \
@@ -252,18 +253,18 @@ remap_end:
     cmp     r3, r2
     strhi   r4, [r2], #4
     bhi     1b
-    
-    /* Set up stack for IRQ mode */ 
+
+    /* Set up stack for IRQ mode */
     msr     cpsr_c, #0xd2
     ldr     sp, =irq_stack
 
-    /* Set up stack for FIQ mode */ 
-    msr     cpsr_c, #0xd1
-    ldr     sp, =fiq_stack
+    /* FIQ mode is unused, thus sp_FIQ is irrelevant for it */
 
-    /* Let svc, abort and undefined modes use irq stack */
+    /* Set up stack for SVC mode */
     msr     cpsr_c, #0xd3
-    ldr     sp, =irq_stack
+    ldr     sp, =svc_stack
+
+    /* Let abort and undefined modes use irq stack */
     msr     cpsr_c, #0xd7
     ldr     sp, =irq_stack
     msr     cpsr_c, #0xdb
@@ -286,7 +287,7 @@ remap_end:
     mrc     p15, 0, r3, c1, c0, 2
     orr     r3, r3, #0xf00000
     mcr     p15, 0, r3, c1, c0, 2
-    
+
     /* Enable VFP */
     mrc     p10, 7, r3, c8, c0, 0
     orr     r3, r3, #1<<30
@@ -314,7 +315,7 @@ remap_end:
     ldr     pc, [pc, #24]
     ldr     pc, [pc, #24]
     subs    pc, lr, #4          @ ldr     pc, [pc, #24]
-    ldr     pc, [pc, #24]
+    subs    pc, lr, #4          @ ldr     pc, [pc, #24]
     .word   newstart
     .word   undef_instr_handler
     .word   software_int_handler
@@ -322,7 +323,7 @@ remap_end:
     .word   data_abort_handler
     .word   reserved_handler
     .word   0                   @ irq_handler
-    .word   fiq_handler
+    .word   0                   @ fiq_handler
 #endif /* BOOTLOADER */
 
     .text
@@ -350,7 +351,7 @@ prefetch_abort_handler:
     b      UIE
 
 data_abort_handler:
-    sub    r0, lr, #8 
+    sub    r0, lr, #8
     mov    r1, #2
     b      UIE
 
@@ -360,8 +361,8 @@ data_abort_handler:
     .space   256*4
 irq_stack:
 
-/* 256 words of FIQ stack */
+/* 256 words of SVC stack */
     .section .bss
     .balign  32
     .space   256*4
-fiq_stack:
+svc_stack:
-- 
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