powerpc: Implement smp_release_cpus() in C not asm

There's no reason for smp_release_cpus() to be asm, and most people can make
more sense of C code. Add an extern declaration to smp.h and remove the custom
one in machine_kexec.c

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

4 files changed, 21 insertions, 39 deletions

diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index ba30e3177b05..45d81976987f 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -1914,24 +1914,6 @@ _GLOBAL(hmt_start_secondary)
         blr
 #endif
 
-#if defined(CONFIG_KEXEC) || defined(CONFIG_SMP)
-_GLOBAL(smp_release_cpus)
-        /* All secondary cpus are spinning on a common
-         * spinloop, release them all now so they can start
-         * to spin on their individual paca spinloops.
-         * For non SMP kernels, the secondary cpus never
-         * get out of the common spinloop.
-         * XXX This does nothing useful on iSeries, secondaries are
-         * already waiting on their paca.
-         */
-        li      r3,1
-        LOADADDR(r5,__secondary_hold_spinloop)
-        std     r3,0(r5)
-        sync
-        blr
-#endif /* CONFIG_SMP */
-
-
 /*
  * We put a few things here that have to be page-aligned.
  * This stuff goes at the beginning of the bss, which is page-aligned.
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index d4a3c5dd1a21..275d86ddd612 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -103,8 +103,6 @@ extern void htab_initialize(void);
 extern void early_init_devtree(void *flat_dt);
 extern void unflatten_device_tree(void);
 
-extern void smp_release_cpus(void);
-
 int have_of = 1;
 int boot_cpuid = 0;
 int boot_cpuid_phys = 0;
@@ -400,6 +398,27 @@ void __init early_setup(unsigned long dt_ptr)
 }
 
 
+#if defined(CONFIG_SMP) || defined(CONFIG_KEXEC)
+void smp_release_cpus(void)
+{
+        extern unsigned long __secondary_hold_spinloop;
+
+        DBG(" -> smp_release_cpus()\n");
+
+        /* All secondary cpus are spinning on a common spinloop, release them
+         * all now so they can start to spin on their individual paca
+         * spinloops. For non SMP kernels, the secondary cpus never get out
+         * of the common spinloop.
+         * This is useless but harmless on iSeries, secondaries are already
+         * waiting on their paca spinloops. */
+
+        __secondary_hold_spinloop = 1;
+        mb();
+
+        DBG(" <- smp_release_cpus()\n");
+}
+#endif /* CONFIG_SMP || CONFIG_KEXEC */
+
 /*
  * Initialize some remaining members of the ppc64_caches and systemcfg structures
  * (at least until we get rid of them completely). This is mostly some
diff --git a/arch/ppc64/kernel/head.S b/arch/ppc64/kernel/head.S
index 0b65efe1682e..db1cf397be2d 100644
--- a/arch/ppc64/kernel/head.S
+++ b/arch/ppc64/kernel/head.S
@@ -1914,24 +1914,6 @@ _GLOBAL(hmt_start_secondary)
         blr
 #endif
 
-#if defined(CONFIG_KEXEC) || defined(CONFIG_SMP)
-_GLOBAL(smp_release_cpus)
-        /* All secondary cpus are spinning on a common
-         * spinloop, release them all now so they can start
-         * to spin on their individual paca spinloops.
-         * For non SMP kernels, the secondary cpus never
-         * get out of the common spinloop.
-         * XXX This does nothing useful on iSeries, secondaries are
-         * already waiting on their paca.
-         */
-        li      r3,1
-        LOADADDR(r5,__secondary_hold_spinloop)
-        std     r3,0(r5)
-        sync
-        blr
-#endif /* CONFIG_SMP */
-
-
 /*
  * We put a few things here that have to be page-aligned.
  * This stuff goes at the beginning of the bss, which is page-aligned.
diff --git a/arch/ppc64/kernel/machine_kexec.c b/arch/ppc64/kernel/machine_kexec.c
index bf7cc4f8210f..ff8679f260f3 100644
--- a/arch/ppc64/kernel/machine_kexec.c
+++ b/arch/ppc64/kernel/machine_kexec.c
@@ -244,7 +244,6 @@ static void kexec_prepare_cpus(void)
 
 static void kexec_prepare_cpus(void)
 {
-        extern void smp_release_cpus(void);
         /*
          * move the secondarys to us so that we can copy
          * the new kernel 0-0x100 safely