[PATCH 1/2 v4] Make iSeries spin on __secondary_hold_spinloop, like pSeries.

[Tony Breeds]

Currently all iSeries secondary CPU's spin directly on the cpu_start in thier
paca.  Make them spin on the global __secondary_hold_spinloop, until after the
pacas have been initialised.

As sfr points out this works because __secondary_hold_spinloop is being set
already, but iSeries isn't looking at it :)

Signed-off-by: Tony Breeds <tony at bakeyournoodle.com>
Acked-by: Stephen Rothwell <sfr at canb.auug.org.au>
---
Changes since v1:
 - Updated commit message.
Changes since v2:
 - Fixed my brain damage, and split out the code that should be in 3/3
Changes since v3:
 - moved in patch series, no funcational changes.


 arch/powerpc/platforms/iseries/exception.S |   27 ++++++++++++++++++++++++++-
 1 files changed, 26 insertions(+), 1 deletions(-)

diff --git a/arch/powerpc/platforms/iseries/exception.S b/arch/powerpc/platforms/iseries/exception.S
index c775cd4..8ff330d 100644
--- a/arch/powerpc/platforms/iseries/exception.S
+++ b/arch/powerpc/platforms/iseries/exception.S
@@ -59,8 +59,33 @@ system_reset_iSeries:
 	andc	r4,r4,r5
 	mtspr	SPRN_CTRLT,r4
 
+/* Spin on __secondary_hold_spinloop until it is updated by the boot cpu. */
+/* In the UP case we'll yeild() later, and we will not access the paca anyway */
+#ifdef CONFIG_SMP
 1:
 	HMT_LOW
+	LOAD_REG_IMMEDIATE(r23, __secondary_hold_spinloop)
+	ld	r23,0(r23)
+	sync
+	LOAD_REG_IMMEDIATE(r3,current_set)
+	sldi	r28,r24,3		/* get current_set[cpu#] */
+	ldx	r3,r3,r28
+	addi	r1,r3,THREAD_SIZE
+	subi	r1,r1,STACK_FRAME_OVERHEAD
+
+	cmpwi	0,r23,0			/* Keep poking the Hypervisor until */
+	bne	2f			/* we're released */
+	/* Let the Hypervisor know we are alive */
+	/* 8002 is a call to HvCallCfg::getLps, a harmless Hypervisor function */
+	lis	r3,0x8002
+	rldicr	r3,r3,32,15		/* r0 = (r3 << 32) & 0xffff000000000000 */
+	li	r0,-1			/* r0=-1 indicates a Hypervisor call */
+	sc				/* Invoke the hypervisor via a system call */
+	b	1b
+#endif
+
+2:
+	HMT_LOW
 #ifdef CONFIG_SMP
 	lbz	r23,PACAPROCSTART(r13)	/* Test if this processor
 					 * should start */
@@ -91,7 +116,7 @@ iSeries_secondary_smp_loop:
 	li	r0,-1			/* r0=-1 indicates a Hypervisor call */
 	sc				/* Invoke the hypervisor via a system call */
 	mfspr	r13,SPRN_SPRG3		/* Put r13 back ???? */
-	b	1b			/* If SMP not configured, secondaries
+	b	2b			/* If SMP not configured, secondaries
 					 * loop forever */
 
 /***  ISeries-LPAR interrupt handlers ***/
-- 
1.5.5.1