powerpc/powernv: abstraction for saving SPRs before entering deep idle states

Create a function for saving SPRs before entering deep idle states.
This function can be reused for POWER9 deep idle states.

Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Shreyas B. Prabhu <shreyas@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/idle_book3s.S

@@ -52,6 +52,36 @@
 
 	.text
 
+/*
+ * Used by threads before entering deep idle states. Saves SPRs
+ * in interrupt stack frame
+ */
+save_sprs_to_stack:
+	/*
+	 * Note all register i.e per-core, per-subcore or per-thread is saved
+	 * here since any thread in the core might wake up first
+	 */
+	mfspr	r3,SPRN_SDR1
+	std	r3,_SDR1(r1)
+	mfspr	r3,SPRN_RPR
+	std	r3,_RPR(r1)
+	mfspr	r3,SPRN_SPURR
+	std	r3,_SPURR(r1)
+	mfspr	r3,SPRN_PURR
+	std	r3,_PURR(r1)
+	mfspr	r3,SPRN_TSCR
+	std	r3,_TSCR(r1)
+	mfspr	r3,SPRN_DSCR
+	std	r3,_DSCR(r1)
+	mfspr	r3,SPRN_AMOR
+	std	r3,_AMOR(r1)
+	mfspr	r3,SPRN_WORT
+	std	r3,_WORT(r1)
+	mfspr	r3,SPRN_WORC
+	std	r3,_WORC(r1)
+
+	blr
+
 /*
  * Used by threads when the lock bit of core_idle_state is set.
  * Threads will spin in HMT_LOW until the lock bit is cleared.
@@ -209,28 +239,8 @@ fastsleep_workaround_at_entry:
 	b	common_enter
 
 enter_winkle:
-	/*
+	bl	save_sprs_to_stack
-	 * Note all register i.e per-core, per-subcore or per-thread is saved
+
-	 * here since any thread in the core might wake up first
-	 */
-	mfspr	r3,SPRN_SDR1
-	std	r3,_SDR1(r1)
-	mfspr	r3,SPRN_RPR
-	std	r3,_RPR(r1)
-	mfspr	r3,SPRN_SPURR
-	std	r3,_SPURR(r1)
-	mfspr	r3,SPRN_PURR
-	std	r3,_PURR(r1)
-	mfspr	r3,SPRN_TSCR
-	std	r3,_TSCR(r1)
-	mfspr	r3,SPRN_DSCR
-	std	r3,_DSCR(r1)
-	mfspr	r3,SPRN_AMOR
-	std	r3,_AMOR(r1)
-	mfspr	r3,SPRN_WORT
-	std	r3,_WORT(r1)
-	mfspr	r3,SPRN_WORC
-	std	r3,_WORC(r1)
 	IDLE_STATE_ENTER_SEQ(PPC_WINKLE)
 
 _GLOBAL(power7_idle)