cpu: Do an isync after setting LPCR

This is required by the architecture and the implementations, I've
observed failures to wake up on big cores without this.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Stewart Smith <stewart@linux.ibm.com>

core/cpu.c

@@ -351,6 +351,7 @@ static void cpu_idle_p8(enum cpu_wake_cause wake_on)
 		lpcr |= SPR_LPCR_P8_PECE2 | SPR_LPCR_P8_PECE3;
 		mtspr(SPR_LPCR, lpcr);
 	}
+	isync();
 
 	/* Enter nap */
 	enter_p8_pm_state(false);
@@ -404,6 +405,7 @@ static void cpu_idle_p9(enum cpu_wake_cause wake_on)
 	}
 
 	mtspr(SPR_LPCR, lpcr);
+	isync();
 
 	if (sreset_enabled) {
 		/* stop with EC=1 (sreset) and ESL=1 (enable thread switch). */
@@ -973,6 +975,7 @@ static void enable_large_dec(bool on)
 		lpcr &= ~SPR_LPCR_P9_LD;
 
 	mtspr(SPR_LPCR, lpcr);
+	isync();
 }
 
 #define HIGH_BIT (1ull << 63)

core/fast-reboot.c

@@ -239,6 +239,7 @@ static void check_split_core(void)
 		/* Setup LPCR to wakeup on external interrupts only */
 		mtspr(SPR_LPCR, ((mfspr(SPR_LPCR) & ~SPR_LPCR_P8_PECE) |
 				 SPR_LPCR_P8_PECE2));
+		isync();
 		/* Go to nap (doesn't return) */
 		enter_nap();
 	}

hw/slw.c

@@ -73,6 +73,7 @@ static void slw_do_rvwinkle(void *data)
 
 	/* Setup LPCR to wakeup on external interrupts only */
 	mtspr(SPR_LPCR, ((lpcr & ~SPR_LPCR_P8_PECE) | SPR_LPCR_P8_PECE2));
+	isync();
 
 	prlog(PR_DEBUG, "SLW: CPU PIR 0x%04x goint to rvwinkle...\n",
 	      cpu->pir);
@@ -99,6 +100,7 @@ static void slw_do_rvwinkle(void *data)
 
 	/* Restore LPCR */
 	mtspr(SPR_LPCR, lpcr);
+	isync();
 
 	/* If we are passed a master pointer we are the designated
 	 * waker, let's proceed. If not, return, we are finished.