From dc559f7cd5d6d11a99b6c29402b31fbb3f3a1db0 Mon Sep 17 00:00:00 2001
From: Olof Johansson <olof@lixom.net>
Date: Wed, 22 Aug 2007 12:26:43 +1000
Subject: [POWERPC] Rework SMP timebase handoff for pasemi
Rework timebase handoff to play nice with configurations with more than
2 cores, as well as with CPU hotplug.
Previous scheme just pushed out the current timebase from the giving
core to all cores without caring if they wanted it or not, nor checking
if they'd taken it. The taking side didn't make sure the giving side
had provided a value yet either. In other words, it was completely broken.
Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>
---
arch/powerpc/platforms/pasemi/setup.c | 24 ++++++++++++++----------
1 file changed, 14 insertions(+), 10 deletions(-)
diff --git a/arch/powerpc/platforms/pasemi/setup.c b/arch/powerpc/platforms/pasemi/setup.c
index ffe6528048..05def6282f 100644
--- a/arch/powerpc/platforms/pasemi/setup.c
+++ b/arch/powerpc/platforms/pasemi/setup.c
@@ -50,26 +50,30 @@ static void pas_restart(char *cmd)
#ifdef CONFIG_SMP
static DEFINE_SPINLOCK(timebase_lock);
+static unsigned long timebase;
static void __devinit pas_give_timebase(void)
{
- unsigned long tb;
-
spin_lock(&timebase_lock);
mtspr(SPRN_TBCTL, TBCTL_FREEZE);
- tb = mftb();
- mtspr(SPRN_TBCTL, TBCTL_UPDATE_LOWER | (tb & 0xffffffff));
- mtspr(SPRN_TBCTL, TBCTL_UPDATE_UPPER | (tb >> 32));
- mtspr(SPRN_TBCTL, TBCTL_RESTART);
+ isync();
+ timebase = get_tb();
spin_unlock(&timebase_lock);
- pr_debug("pas_give_timebase: cpu %d gave tb %lx\n",
- smp_processor_id(), tb);
+
+ while (timebase)
+ barrier();
+ mtspr(SPRN_TBCTL, TBCTL_RESTART);
}
static void __devinit pas_take_timebase(void)
{
- pr_debug("pas_take_timebase: cpu %d has tb %lx\n",
- smp_processor_id(), mftb());
+ while (!timebase)
+ smp_rmb();
+
+ spin_lock(&timebase_lock);
+ set_tb(timebase >> 32, timebase & 0xffffffff);
+ timebase = 0;
+ spin_unlock(&timebase_lock);
}
struct smp_ops_t pas_smp_ops = {
--
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