remap-vec.patch

Uboot常用的移植patches, 方便定制移植到s3c2440

This patch changes how we avoid getting killed by an interrupt if the vectors
at address zero and the u-boot we're running don't agree.

Instead of copying the vectors to SteppingStone, which introduced the very
ugly need to wait until AUX was released, and didn't work for NAND, we copy
the vectors to the beginning of our DRAM and map the address range 0x0...
to 0x3...

This obsoletes nor-irqvec.patch

We could probably also use the same logic to replace
uboot-s3c2410-norelocate_irqvec_cpy.patch
but then, never change a running system ;-)

Note: this is still experimental. Please give it a solid beating.

- Werner

Index: u-boot/board/neo1973/gta02/gta02.c
===================================================================
--- u-boot.orig/board/neo1973/gta02/gta02.c
+++ u-boot/board/neo1973/gta02/gta02.c
@@ -215,17 +215,28 @@
 	dcache_enable();
 
 	/*
-	 * Since the NOR is replaced by SteppingStone when the AUX button is
-	 * released, we have to wait for this and copy our exception vectors
-	 * before we can let u-boot enable interrupts.
+	 * Since the NOR at address 0 is replaced by SteppingStone when the AUX
+	 * button is released, we would crash when an interrupt arrives (e.g.,
+	 * on USB insertion).
+	 *
+	 * We solve this as follows: we copy the vector table to RAM at address
+	 * 0x30000000 and then use the PID feature in the 920T MMU to map all
+	 * addresses in the range 0x0....... to 0x3....... without actually
+	 * setting up page mappings in the MMU. Thus, vectors are then
+	 * retrieved from their location in RAM.
+	 *
+	 * Note that the mapping is done in lib_arm/interrupts.c, so that it
+	 * automatically tracks whether we allow interrupts or not. This is
+	 * particularly necessary when we boot, since the operating system may
+	 * not expect to find this sort of mapping to be active.
 	 */
-	if (booted_from_nor) {
+#ifdef CONFIG_GTA02_REVISION
+	{
 		extern char _start;
 
-		while (neo1973_aux_key_pressed());
-		memcpy((void *) 0, &_start, 0x40);
+		memcpy((void *) 0x30000000, &_start, 0x40);
 	}
-
+#endif
 	return 0;
 }
 
Index: u-boot/lib_arm/interrupts.c
===================================================================
--- u-boot.orig/lib_arm/interrupts.c
+++ u-boot/lib_arm/interrupts.c
@@ -43,9 +43,14 @@
 void enable_interrupts (void)
 {
 	unsigned long temp;
-	__asm__ __volatile__("mrs %0, cpsr\n"
+	__asm__ __volatile__(
+#ifdef CONFIG_GTA02_REVISION
+			     "mov %0, #0x30000000\n"
+			     "mcr p15, 0, %0, c13, c0\n"
+#endif
+			     "mrs %0, cpsr\n"
 			     "bic %0, %0, #0x80\n"
-			     "msr cpsr_c, %0"
+			     "msr cpsr_c, %0\n"
 			     : "=r" (temp)
 			     :
 			     : "memory");
@@ -61,7 +66,11 @@
 	unsigned long old,temp;
 	__asm__ __volatile__("mrs %0, cpsr\n"
 			     "orr %1, %0, #0xc0\n"
-			     "msr cpsr_c, %1"
+			     "msr cpsr_c, %1\n"
+#ifdef CONFIG_GTA02_REVISION
+			     "mov %1, #0\n"
+			     "mcr p15, 0, %1, c13, c0\n"
+#endif
 			     : "=r" (old), "=r" (temp)
 			     :
 			     : "memory");