ARM: 5899/2: arm: provide a mechanism to reserve performance counters

To add support for perf events and to allow the hardware counters to be
shared with oprofile, we need a way to reserve access to the pmu
(performance monitor unit). Platforms with PMU interrupts should
register the interrupts in arch/arm/kernel/pmu.c

Signed-off-by: Jamie Iles <jamie.iles@picochip.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

4 files changed, 184 insertions, 0 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 233a222752c0..9e08891062bf 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -863,6 +863,11 @@ config XSCALE_PMU
         depends on CPU_XSCALE && !XSCALE_PMU_TIMER
         default y
 
+config CPU_HAS_PMU
+        depends on CPU_V6 || CPU_V7 || XSCALE_PMU
+        default y
+        bool
+
 if !MMU
 source "arch/arm/Kconfig-nommu"
 endif
diff --git a/arch/arm/include/asm/pmu.h b/arch/arm/include/asm/pmu.h
new file mode 100644
index 000000000000..2829b9f981a1
--- /dev/null
+++ b/arch/arm/include/asm/pmu.h
@@ -0,0 +1,75 @@
+/*
+ *  linux/arch/arm/include/asm/pmu.h
+ *
+ *  Copyright (C) 2009 picoChip Designs Ltd, Jamie Iles
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#ifndef __ARM_PMU_H__
+#define __ARM_PMU_H__
+
+#ifdef CONFIG_CPU_HAS_PMU
+
+struct pmu_irqs {
+        const int   *irqs;
+        int         num_irqs;
+};
+
+/**
+ * reserve_pmu() - reserve the hardware performance counters
+ *
+ * Reserve the hardware performance counters in the system for exclusive use.
+ * The 'struct pmu_irqs' for the system is returned on success, ERR_PTR()
+ * encoded error on failure.
+ */
+extern const struct pmu_irqs *
+reserve_pmu(void);
+
+/**
+ * release_pmu() - Relinquish control of the performance counters
+ *
+ * Release the performance counters and allow someone else to use them.
+ * Callers must have disabled the counters and released IRQs before calling
+ * this. The 'struct pmu_irqs' returned from reserve_pmu() must be passed as
+ * a cookie.
+ */
+extern int
+release_pmu(const struct pmu_irqs *irqs);
+
+/**
+ * init_pmu() - Initialise the PMU.
+ *
+ * Initialise the system ready for PMU enabling. This should typically set the
+ * IRQ affinity and nothing else. The users (oprofile/perf events etc) will do
+ * the actual hardware initialisation.
+ */
+extern int
+init_pmu(void);
+
+#else /* CONFIG_CPU_HAS_PMU */
+
+static inline const struct pmu_irqs *
+reserve_pmu(void)
+{
+        return ERR_PTR(-ENODEV);
+}
+
+static inline int
+release_pmu(const struct pmu_irqs *irqs)
+{
+        return -ENODEV;
+}
+
+static inline int
+init_pmu(void)
+{
+        return -ENODEV;
+}
+
+#endif /* CONFIG_CPU_HAS_PMU */
+
+#endif /* __ARM_PMU_H__ */
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index dd00f747e2ad..216890d804c2 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -46,6 +46,7 @@ obj-$(CONFIG_CPU_XSCALE)	+= xscale-cp0.o
 obj-$(CONFIG_CPU_XSC3)          += xscale-cp0.o
 obj-$(CONFIG_CPU_MOHAWK)        += xscale-cp0.o
 obj-$(CONFIG_IWMMXT)            += iwmmxt.o
+obj-$(CONFIG_CPU_HAS_PMU)       += pmu.o
 AFLAGS_iwmmxt.o                 := -Wa,-mcpu=iwmmxt
 
 ifneq ($(CONFIG_ARCH_EBSA110),y)
diff --git a/arch/arm/kernel/pmu.c b/arch/arm/kernel/pmu.c
new file mode 100644
index 000000000000..a124312e343f
--- /dev/null
+++ b/arch/arm/kernel/pmu.c
@@ -0,0 +1,103 @@
+/*
+ *  linux/arch/arm/kernel/pmu.c
+ *
+ *  Copyright (C) 2009 picoChip Designs Ltd, Jamie Iles
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/cpumask.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+#include <asm/pmu.h>
+
+/*
+ * Define the IRQs for the system. We could use something like a platform
+ * device but that seems fairly heavyweight for this. Also, the performance
+ * counters can't be removed or hotplugged.
+ *
+ * Ordering is important: init_pmu() will use the ordering to set the affinity
+ * to the corresponding core. e.g. the first interrupt will go to cpu 0, the
+ * second goes to cpu 1 etc.
+ */
+static const int irqs[] = {
+#if defined(CONFIG_ARCH_OMAP2)
+        3,
+#elif defined(CONFIG_ARCH_BCMRING)
+        IRQ_PMUIRQ,
+#elif defined(CONFIG_MACH_REALVIEW_EB)
+        IRQ_EB11MP_PMU_CPU0,
+        IRQ_EB11MP_PMU_CPU1,
+        IRQ_EB11MP_PMU_CPU2,
+        IRQ_EB11MP_PMU_CPU3,
+#elif defined(CONFIG_ARCH_OMAP3)
+        INT_34XX_BENCH_MPU_EMUL,
+#elif defined(CONFIG_ARCH_IOP32X)
+        IRQ_IOP32X_CORE_PMU,
+#elif defined(CONFIG_ARCH_IOP33X)
+        IRQ_IOP33X_CORE_PMU,
+#elif defined(CONFIG_ARCH_PXA)
+        IRQ_PMU,
+#endif
+};
+
+static const struct pmu_irqs pmu_irqs = {
+        .irqs       = irqs,
+        .num_irqs   = ARRAY_SIZE(irqs),
+};
+
+static volatile long pmu_lock;
+
+const struct pmu_irqs *
+reserve_pmu(void)
+{
+        return test_and_set_bit_lock(0, &pmu_lock) ? ERR_PTR(-EBUSY) :
+                &pmu_irqs;
+}
+EXPORT_SYMBOL_GPL(reserve_pmu);
+
+int
+release_pmu(const struct pmu_irqs *irqs)
+{
+        if (WARN_ON(irqs != &pmu_irqs))
+                return -EINVAL;
+        clear_bit_unlock(0, &pmu_lock);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(release_pmu);
+
+static int
+set_irq_affinity(int irq,
+                 unsigned int cpu)
+{
+#ifdef CONFIG_SMP
+        int err = irq_set_affinity(irq, cpumask_of(cpu));
+        if (err)
+                pr_warning("unable to set irq affinity (irq=%d, cpu=%u)\n",
+                           irq, cpu);
+        return err;
+#else
+        return 0;
+#endif
+}
+
+int
+init_pmu(void)
+{
+        int i, err = 0;
+
+        for (i = 0; i < pmu_irqs.num_irqs; ++i) {
+                err = set_irq_affinity(pmu_irqs.irqs[i], i);
+                if (err)
+                        break;
+        }
+
+        return err;
+}
+EXPORT_SYMBOL_GPL(init_pmu);