MIPS: Add new GIC clocksource.

Add new clocksource that uses the counter present on the MIPS
Global Interrupt Controller.

Signed-off-by: Steven J. Hill <sjhill@mips.com>
Patchwork: http://patchwork.linux-mips.org/patch/4681/
Signed-off-by: John Crispin <blogic@openwrt.org>

1 files changed, 49 insertions, 0 deletions

diff --git a/arch/mips/kernel/csrc-gic.c b/arch/mips/kernel/csrc-gic.c
new file mode 100644
index 000000000000..5dca24bce51b
--- /dev/null
+++ b/arch/mips/kernel/csrc-gic.c
@@ -0,0 +1,49 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2012 MIPS Technologies, Inc.  All rights reserved.
+ */
+#include <linux/clocksource.h>
+#include <linux/init.h>
+
+#include <asm/time.h>
+#include <asm/gic.h>
+
+static cycle_t gic_hpt_read(struct clocksource *cs)
+{
+	unsigned int hi, hi2, lo;
+
+	do {
+		GICREAD(GIC_REG(SHARED, GIC_SH_COUNTER_63_32), hi);
+		GICREAD(GIC_REG(SHARED, GIC_SH_COUNTER_31_00), lo);
+		GICREAD(GIC_REG(SHARED, GIC_SH_COUNTER_63_32), hi2);
+	} while (hi2 != hi);
+
+	return (((cycle_t) hi) << 32) + lo;
+}
+
+static struct clocksource gic_clocksource = {
+	.name	= "GIC",
+	.read	= gic_hpt_read,
+	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+void __init gic_clocksource_init(unsigned int frequency)
+{
+	unsigned int config, bits;
+
+	/* Calculate the clocksource mask. */
+	GICREAD(GIC_REG(SHARED, GIC_SH_CONFIG), config);
+	bits = 32 + ((config & GIC_SH_CONFIG_COUNTBITS_MSK) >>
+		(GIC_SH_CONFIG_COUNTBITS_SHF - 2));
+
+	/* Set clocksource mask. */
+	gic_clocksource.mask = CLOCKSOURCE_MASK(bits);
+
+	/* Calculate a somewhat reasonable rating value. */
+	gic_clocksource.rating = 200 + frequency / 10000000;
+
+	clocksource_register_hz(&gic_clocksource, frequency);
+}