[MIPS] Workaround for RM7000 WAIT instruction aka erratum 38
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index c6b8b07..06448a9 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -75,6 +75,27 @@
local_irq_enable();
}
+/*
+ * The RM7000 variant has to handle erratum 38. The workaround is to not
+ * have any pending stores when the WAIT instruction is executed.
+ */
+static void rm7k_wait_irqoff(void)
+{
+ local_irq_disable();
+ if (!need_resched())
+ __asm__(
+ " .set push \n"
+ " .set mips3 \n"
+ " .set noat \n"
+ " mfc0 $1, $12 \n"
+ " sync \n"
+ " mtc0 $1, $12 # stalls until W stage \n"
+ " wait \n"
+ " mtc0 $1, $12 # stalls until W stage \n"
+ " .set pop \n");
+ local_irq_enable();
+}
+
/* The Au1xxx wait is available only if using 32khz counter or
* external timer source, but specifically not CP0 Counter. */
int allow_au1k_wait;
@@ -132,7 +153,6 @@
case CPU_R4700:
case CPU_R5000:
case CPU_NEVADA:
- case CPU_RM7000:
case CPU_4KC:
case CPU_4KEC:
case CPU_4KSC:
@@ -142,6 +162,10 @@
cpu_wait = r4k_wait;
break;
+ case CPU_RM7000:
+ cpu_wait = rm7k_wait_irqoff;
+ break;
+
case CPU_24K:
case CPU_34K:
cpu_wait = r4k_wait;