powerpc/8xx: rewrite flush_instruction_cache() in C

On PPC8xx, flushing instruction cache is performed by writing
in register SPRN_IC_CST. This registers suffers CPU6 ERRATA.
The patch rewrites the fonction in C so that CPU6 ERRATA will
be handled transparently
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Scott Wood <oss@buserror.net>

arch/powerpc/kernel/misc_32.S

@@ -296,12 +296,9 @@ _GLOBAL(real_writeb)
  * Flush instruction cache.
  * This is a no-op on the 601.
  */
+#ifndef CONFIG_PPC_8xx
 _GLOBAL(flush_instruction_cache)
-#if defined(CONFIG_8xx)
-	isync
-	lis	r5, IDC_INVALL@h
-	mtspr	SPRN_IC_CST, r5
-#elif defined(CONFIG_4xx)
+#if defined(CONFIG_4xx)
 #ifdef CONFIG_403GCX
 	li      r3, 512
 	mtctr   r3
@@ -334,9 +331,10 @@ END_FTR_SECTION_IFSET(CPU_FTR_UNIFIED_ID_CACHE)
 	mfspr	r3,SPRN_HID0
 	ori	r3,r3,HID0_ICFI
 	mtspr	SPRN_HID0,r3
-#endif /* CONFIG_8xx/4xx */
+#endif /* CONFIG_4xx */
 	isync
 	blr
+#endif /* CONFIG_PPC_8xx */
 
 /*
  * Write any modified data cache blocks out to memory

arch/powerpc/mm/8xx_mmu.c

@@ -132,3 +132,10 @@ void set_context(unsigned long id, pgd_t *pgd)
 	/* sync */
 	mb();
 }
+
+void flush_instruction_cache(void)
+{
+	isync();
+	mtspr(SPRN_IC_CST, IDC_INVALL);
+	isync();
+}