[POWERPC] Make iSeries spin on __secondary_hold_spinloop, like pSeries

Currently all iSeries secondary CPUs spin directly on the cpu_start
field in their paca.  Make them spin on the global
__secondary_hold_spinloop until after the pacas have been initialised.

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

Signed-off-by: Tony Breeds <tony@bakeyournoodle.com>
Acked-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 26 insertions, 1 deletions

diff --git a/arch/powerpc/platforms/iseries/exception.S b/arch/powerpc/platforms/iseries/exception.S
index c775cd4b3d6e..8ff330d026ca 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 ***/