[PATCH 4/4] x86: Introduce Numachip2 timer mechanisms

[Daniel J Blueman <daniel@numascale.com>]

Add 1GHz 64-bit Numachip2 clocksource timer support for accurate
system-wide timekeeping, as core TSCs are unsynchronised.

Additionally, add a per-core clockevent mechanism that interrupts via the
platform IPI vector after a programmed period.

Signed-off-by: Daniel J Blueman <daniel@numascale.com>
Acked-by: Steffen Persvold <sp@numascale.com>
---
 arch/x86/include/asm/numachip/numachip_csr.h | 9 +++++++++
 drivers/clocksource/Makefile                 | 1 +
 2 files changed, 10 insertions(+)

diff --git a/arch/x86/include/asm/numachip/numachip_csr.h b/arch/x86/include/asm/numachip/numachip_csr.h
index e09d845..29719ee 100644
--- a/arch/x86/include/asm/numachip/numachip_csr.h
+++ b/arch/x86/include/asm/numachip/numachip_csr.h
@@ -59,6 +59,10 @@ static inline void write_lcsr(unsigned long offset, unsigned int val)
 #define NUMACHIP2_LCSR_BASE       0xf0000000UL
 #define NUMACHIP2_LCSR_SIZE       0x1000000UL
 #define NUMACHIP2_APIC_ICR        0x100000
+#define NUMACHIP2_TIMER_DEADLINE  0x200000
+#define NUMACHIP2_TIMER_INT       0x200008
+#define NUMACHIP2_TIMER_NOW       0x200018
+#define NUMACHIP2_TIMER_RESET     0x200020
 
 static inline void __iomem *numachip2_lcsr_address(unsigned long offset)
 {
@@ -86,4 +90,9 @@ static inline void numachip2_write64_lcsr(unsigned long offset, u64 val)
 	writeq(val, numachip2_lcsr_address(offset));
 }
 
+static inline unsigned int numachip2_timer(void)
+{
+	return (smp_processor_id() % 48) << 6;
+}
+
 #endif /* _ASM_X86_NUMACHIP_NUMACHIP_CSR_H */
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 5c00863..57dfad3 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -62,3 +62,4 @@ obj-$(CONFIG_H8300)			+= h8300_timer8.o
 obj-$(CONFIG_H8300_TMR16)		+= h8300_timer16.o
 obj-$(CONFIG_H8300_TPU)			+= h8300_tpu.o
 obj-$(CONFIG_CLKSRC_ST_LPC)		+= clksrc_st_lpc.o
+obj-$(CONFIG_X86_NUMACHIP)		+= numachip.o
diff --git a/drivers/clocksource/numachip.c b/drivers/clocksource/numachip.c
new file mode 100644
index 0000000..5e4f90e
--- /dev/null
+++ b/drivers/clocksource/numachip.c
@@ -0,0 +1,95 @@
+/*
+ *
+ * Copyright (C) 2015 Numascale AS. All rights reserved.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/clockchips.h>
+
+#include <asm/irq.h>
+#include <asm/numachip/numachip.h>
+#include <asm/numachip/numachip_csr.h>
+
+static DEFINE_PER_CPU(struct clock_event_device, cpu_ced);
+
+static cycles_t numachip2_timer_read(struct clocksource *cs)
+{
+	return numachip2_read64_lcsr(NUMACHIP2_TIMER_NOW);
+}
+
+static struct clocksource numachip2_clocksource = {
+	.name            = "numachip2",
+	.rating          = 295,
+	.read            = numachip2_timer_read,
+	.mask            = CLOCKSOURCE_MASK(64),
+	.flags           = CLOCK_SOURCE_IS_CONTINUOUS,
+	.mult            = 1,
+	.shift           = 0,
+};
+
+static int numachip2_set_next_event(unsigned long delta, struct clock_event_device *ced)
+{
+	numachip2_write64_lcsr(NUMACHIP2_TIMER_DEADLINE + numachip2_timer(),
+		delta);
+	return 0;
+}
+
+static struct clock_event_device numachip2_clockevent = {
+	.name		     = "numachip2",
+	.rating		     = 400,
+	.set_next_event  = numachip2_set_next_event,
+	.features	     = CLOCK_EVT_FEAT_ONESHOT,
+	.mult            = 1,
+	.shift           = 0,
+	.min_delta_ns    = 1250,
+	.max_delta_ns    = LONG_MAX,
+};
+
+static void numachip_timer_interrupt(void)
+{
+	struct clock_event_device *ced = this_cpu_ptr(&cpu_ced);
+
+	ced->event_handler(ced);
+}
+
+static __init void numachip_timer_each(struct work_struct *work)
+{
+	unsigned local_apicid = __this_cpu_read(x86_cpu_to_apicid) & 0xff;
+	struct clock_event_device *ced = this_cpu_ptr(&cpu_ced);
+
+	/* Setup IPI vector to local core and relative timing mode */
+	numachip2_write64_lcsr(NUMACHIP2_TIMER_INT + numachip2_timer(),
+		| (X86_PLATFORM_IPI_VECTOR << 14) |
+		(local_apicid << 6));
+
+	*ced = numachip2_clockevent;
+	ced->cpumask = cpumask_of(smp_processor_id());
+	clockevents_register_device(ced);
+}
+
+static int __init numachip_timer_init(void)
+{
+	if (numachip_system != 2)
+		return -ENODEV;
+
+	/* Reset timer */
+	numachip2_write64_lcsr(NUMACHIP2_TIMER_RESET, 0);
+	clocksource_register_hz(&numachip2_clocksource, NSEC_PER_SEC);
+
+	/* Setup per-cpu clockevents */
+	x86_platform_ipi_callback = numachip_timer_interrupt;
+	schedule_on_each_cpu(&numachip_timer_each);
+
+	return 0;
+}
+
+arch_initcall(numachip_timer_init);
-- 
2.5.0