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authorRalf Baechle <ralf@linux-mips.org>2008-04-28 17:14:26 +0100
committerRalf Baechle <ralf@linux-mips.org>2008-04-28 17:14:26 +0100
commit39b8d5254246ac56342b72f812255c8f7a74dca9 (patch)
treea9ec6bfb5d09a8367c34cc2067328d1b49bb46c1 /arch/mips/kernel/sync-r4k.c
parent308402445e005a039a72b315cd9b5ceeaea0063c (diff)
[MIPS] Add support for MIPS CMP platform.
Signed-off-by: Chris Dearman <chris@mips.com> Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp> Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips/kernel/sync-r4k.c')
-rw-r--r--arch/mips/kernel/sync-r4k.c159
1 files changed, 159 insertions, 0 deletions
diff --git a/arch/mips/kernel/sync-r4k.c b/arch/mips/kernel/sync-r4k.c
new file mode 100644
index 000000000000..9021108eb9c1
--- /dev/null
+++ b/arch/mips/kernel/sync-r4k.c
@@ -0,0 +1,159 @@
+/*
+ * Count register synchronisation.
+ *
+ * All CPUs will have their count registers synchronised to the CPU0 expirelo
+ * value. This can cause a small timewarp for CPU0. All other CPU's should
+ * not have done anything significant (but they may have had interrupts
+ * enabled briefly - prom_smp_finish() should not be responsible for enabling
+ * interrupts...)
+ *
+ * FIXME: broken for SMTC
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/irqflags.h>
+#include <linux/r4k-timer.h>
+
+#include <asm/atomic.h>
+#include <asm/barrier.h>
+#include <asm/cpumask.h>
+#include <asm/mipsregs.h>
+
+static atomic_t __initdata count_start_flag = ATOMIC_INIT(0);
+static atomic_t __initdata count_count_start = ATOMIC_INIT(0);
+static atomic_t __initdata count_count_stop = ATOMIC_INIT(0);
+
+#define COUNTON 100
+#define NR_LOOPS 5
+
+void __init synchronise_count_master(void)
+{
+ int i;
+ unsigned long flags;
+ unsigned int initcount;
+ int nslaves;
+
+#ifdef CONFIG_MIPS_MT_SMTC
+ /*
+ * SMTC needs to synchronise per VPE, not per CPU
+ * ignore for now
+ */
+ return;
+#endif
+
+ pr_info("Checking COUNT synchronization across %u CPUs: ",
+ num_online_cpus());
+
+ local_irq_save(flags);
+
+ /*
+ * Notify the slaves that it's time to start
+ */
+ atomic_set(&count_start_flag, 1);
+ smp_wmb();
+
+ /* Count will be initialised to expirelo for all CPU's */
+ initcount = expirelo;
+
+ /*
+ * We loop a few times to get a primed instruction cache,
+ * then the last pass is more or less synchronised and
+ * the master and slaves each set their cycle counters to a known
+ * value all at once. This reduces the chance of having random offsets
+ * between the processors, and guarantees that the maximum
+ * delay between the cycle counters is never bigger than
+ * the latency of information-passing (cachelines) between
+ * two CPUs.
+ */
+
+ nslaves = num_online_cpus()-1;
+ for (i = 0; i < NR_LOOPS; i++) {
+ /* slaves loop on '!= ncpus' */
+ while (atomic_read(&count_count_start) != nslaves)
+ mb();
+ atomic_set(&count_count_stop, 0);
+ smp_wmb();
+
+ /* this lets the slaves write their count register */
+ atomic_inc(&count_count_start);
+
+ /*
+ * Everyone initialises count in the last loop:
+ */
+ if (i == NR_LOOPS-1)
+ write_c0_count(initcount);
+
+ /*
+ * Wait for all slaves to leave the synchronization point:
+ */
+ while (atomic_read(&count_count_stop) != nslaves)
+ mb();
+ atomic_set(&count_count_start, 0);
+ smp_wmb();
+ atomic_inc(&count_count_stop);
+ }
+ /* Arrange for an interrupt in a short while */
+ write_c0_compare(read_c0_count() + COUNTON);
+
+ local_irq_restore(flags);
+
+ /*
+ * i386 code reported the skew here, but the
+ * count registers were almost certainly out of sync
+ * so no point in alarming people
+ */
+ printk("done.\n");
+}
+
+void __init synchronise_count_slave(void)
+{
+ int i;
+ unsigned long flags;
+ unsigned int initcount;
+ int ncpus;
+
+#ifdef CONFIG_MIPS_MT_SMTC
+ /*
+ * SMTC needs to synchronise per VPE, not per CPU
+ * ignore for now
+ */
+ return;
+#endif
+
+ local_irq_save(flags);
+
+ /*
+ * Not every cpu is online at the time this gets called,
+ * so we first wait for the master to say everyone is ready
+ */
+
+ while (!atomic_read(&count_start_flag))
+ mb();
+
+ /* Count will be initialised to expirelo for all CPU's */
+ initcount = expirelo;
+
+ ncpus = num_online_cpus();
+ for (i = 0; i < NR_LOOPS; i++) {
+ atomic_inc(&count_count_start);
+ while (atomic_read(&count_count_start) != ncpus)
+ mb();
+
+ /*
+ * Everyone initialises count in the last loop:
+ */
+ if (i == NR_LOOPS-1)
+ write_c0_count(initcount);
+
+ atomic_inc(&count_count_stop);
+ while (atomic_read(&count_count_stop) != ncpus)
+ mb();
+ }
+ /* Arrange for an interrupt in a short while */
+ write_c0_compare(read_c0_count() + COUNTON);
+
+ local_irq_restore(flags);
+}
+#undef NR_LOOPS
+#endif