powerpc/85xx: add hardware automatically enter pw20 state

Using hardware features make core automatically enter PW20 state.
Set a TB count to hardware, the effective count begins when PW10
is entered. When the effective period has expired, the core will
proceed from PW10 to PW20 if no exit conditions have occurred during
the period.
Signed-off-by: Wang Dongsheng <dongsheng.wang@freescale.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>

arch/powerpc/kernel/cpu_setup_fsl_booke.S

@@ -53,6 +53,25 @@ _GLOBAL(__e500_dcache_setup)
 	isync
 	blr
 
+/*
+ * FIXME - we haven't yet done testing to determine a reasonable default
+ * value for PW20_WAIT_IDLE_BIT.
+ */
+#define PW20_WAIT_IDLE_BIT		50 /* 1ms, TB frequency is 41.66MHZ */
+_GLOBAL(setup_pw20_idle)
+	mfspr	r3, SPRN_PWRMGTCR0
+
+	/* Set PW20_WAIT bit, enable pw20 state*/
+	ori	r3, r3, PWRMGTCR0_PW20_WAIT
+	li	r11, PW20_WAIT_IDLE_BIT
+
+	/* Set Automatic PW20 Core Idle Count */
+	rlwimi	r3, r11, PWRMGTCR0_PW20_ENT_SHIFT, PWRMGTCR0_PW20_ENT
+
+	mtspr	SPRN_PWRMGTCR0, r3
+
+	blr
+
 /*
  * FIXME - we haven't yet done testing to determine a reasonable default
  * value for AV_WAIT_IDLE_BIT.
@@ -83,6 +102,7 @@ _GLOBAL(__setup_cpu_e6500)
 	bl	.setup_lrat_ivor
 1:
 #endif
+	bl	setup_pw20_idle
 	bl	setup_altivec_idle
 	bl	__setup_cpu_e5500
 	mtlr	r6
@@ -151,6 +171,7 @@ _GLOBAL(__restore_cpu_e6500)
 	beq	1f
 	bl	.setup_lrat_ivor
 1:
+	bl	.setup_pw20_idle
 	bl	.setup_altivec_idle
 	bl	__restore_cpu_e5500
 	mtlr	r5