/*

Mikey and I noticed that the decrementer isn't firing when
it should. If a decrementer is pending and an mtmsrd(MSR_EE) is
executed then we should take the decrementer exception. From the PPC AS:

  If MSR EE = 0 and an External, Decrementer, or Per-
  formance Monitor exception is pending, executing
  an mtmsrd instruction that sets MSR EE to 1 will
  cause the interrupt to occur before the next instruc-
  tion is executed, if no higher priority exception
  exists

A test case is below. r31 is incremented for every decrementer
exception.

powerpc64le-linux-gcc -c test.S
powerpc64le-linux-ld -Ttext=0x0 -o test.elf test.o
powerpc64le-linux-objcopy -O binary test.elf test.bin

qemu-system-ppc64 -M powernv -cpu POWER9 -nographic -bios test.bin

"info registers" shows it looping in the lower loop, ie the
decrementer exception was never taken.

r31 never moves. If I build with:

powerpc64le-linux-gcc -DFIX_BROKEN -c test.S

I see r31 move.

*/

#include <ppc-asm.h>

/* Load an immediate 64-bit value into a register */
#define LOAD_IMM64(r, e)			\
	lis	r,(e)@highest;			\
	ori	r,r,(e)@higher;			\
	rldicr	r,r, 32, 31;			\
	oris	r,r, (e)@h;			\
	ori	r,r, (e)@l;

#define FIXUP_ENDIAN						   \
	tdi   0,0,0x48;	  /* Reverse endian of b . + 8		*/ \
	b     191f;	  /* Skip trampoline if endian is good	*/ \
	.long 0xa600607d; /* mfmsr r11				*/ \
	.long 0x01006b69; /* xori r11,r11,1			*/ \
	.long 0x05009f42; /* bcl 20,31,$+4			*/ \
	.long 0xa602487d; /* mflr r10				*/ \
	.long 0x14004a39; /* addi r10,r10,20			*/ \
	.long 0xa64b5a7d; /* mthsrr0 r10			*/ \
	.long 0xa64b7b7d; /* mthsrr1 r11			*/ \
	.long 0x2402004c; /* hrfid				*/ \
191:

	.= 0x0
.globl _start
_start:
	b	1f

	.= 0x10
	FIXUP_ENDIAN
	b	1f

	.= 0x100
1:
	FIXUP_ENDIAN
	b	__initialize

#define EXCEPTION(nr)		\
	.= nr			;\
	b	.

	/* More exception stubs */
	EXCEPTION(0x300)
	EXCEPTION(0x380)
	EXCEPTION(0x400)
	EXCEPTION(0x480)
	EXCEPTION(0x500)
	EXCEPTION(0x600)
	EXCEPTION(0x700)
	EXCEPTION(0x800)

	.= 0x900
	LOAD_IMM64(r0, 0x1000000)
	mtdec	r0
	addi	r31,r31,1
	rfid

	EXCEPTION(0x980)
	EXCEPTION(0xa00)
	EXCEPTION(0xb00)
	EXCEPTION(0xc00)
	EXCEPTION(0xd00)
	EXCEPTION(0xe00)
	EXCEPTION(0xe20)
	EXCEPTION(0xe40)
	EXCEPTION(0xe60)
	EXCEPTION(0xe80)
	EXCEPTION(0xf00)
	EXCEPTION(0xf20)
	EXCEPTION(0xf40)
	EXCEPTION(0xf60)
	EXCEPTION(0xf80)
	EXCEPTION(0x1000)
	EXCEPTION(0x1100)
	EXCEPTION(0x1200)
	EXCEPTION(0x1300)
	EXCEPTION(0x1400)
	EXCEPTION(0x1500)
	EXCEPTION(0x1600)

__initialize:
	/* SF, HV, EE, RI, LE */
	LOAD_IMM64(r0, 0x9000000000008003)
	mtmsrd	r0
	
	/* HID0: HILE */
	LOAD_IMM64(r0, 0x800000000000000)
	mtspr	0x3f0,r0

	LOAD_IMM64(r0, 0x1000000)
	mtdec r0

1:	LOAD_IMM64(r30,0x8000)
	mtmsrd	r30,1

	/* We should take the decrementer here */
#ifdef FIX_BROKEN
	LOAD_IMM64(r29,0x100000000)
	mtctr	r29
2:	bdnz	2b
#endif

	li	r30,0x0
	mtmsrd	r30,1
	b	1b