1 files changed, 90 insertions, 0 deletions
diff --git a/arch/mips/kernel/csrc-r4k.c b/arch/mips/kernel/csrc-r4k.c
new file mode 100644
index 000000000..eed099f35
--- /dev/null
+++ b/arch/mips/kernel/csrc-r4k.c
@@ -0,0 +1,90 @@
+/*
+ * 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) 2007 by Ralf Baechle
+ */
+#include <linux/clocksource.h>
+#include <linux/init.h>
+#include <linux/sched_clock.h>
+
+#include <asm/time.h>
+
+static u64 c0_hpt_read(struct clocksource *cs)
+{
+	return read_c0_count();
+}
+
+static struct clocksource clocksource_mips = {
+	.name		= "MIPS",
+	.read		= c0_hpt_read,
+	.mask		= CLOCKSOURCE_MASK(32),
+	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static u64 __maybe_unused notrace r4k_read_sched_clock(void)
+{
+	return read_c0_count();
+}
+
+static inline unsigned int rdhwr_count(void)
+{
+	unsigned int count;
+
+	__asm__ __volatile__(
+	"	.set push\n"
+	"	.set mips32r2\n"
+	"	rdhwr	%0, $2\n"
+	"	.set pop\n"
+	: "=r" (count));
+
+	return count;
+}
+
+static bool rdhwr_count_usable(void)
+{
+	unsigned int prev, curr, i;
+
+	/*
+	 * Older QEMUs have a broken implementation of RDHWR for the CP0 count
+	 * which always returns a constant value. Try to identify this and don't
+	 * use it in the VDSO if it is broken. This workaround can be removed
+	 * once the fix has been in QEMU stable for a reasonable amount of time.
+	 */
+	for (i = 0, prev = rdhwr_count(); i < 100; i++) {
+		curr = rdhwr_count();
+
+		if (curr != prev)
+			return true;
+
+		prev = curr;
+	}
+
+	pr_warn("Not using R4K clocksource in VDSO due to broken RDHWR\n");
+	return false;
+}
+
+int __init init_r4k_clocksource(void)
+{
+	if (!cpu_has_counter || !mips_hpt_frequency)
+		return -ENXIO;
+
+	/* Calculate a somewhat reasonable rating value */
+	clocksource_mips.rating = 200 + mips_hpt_frequency / 10000000;
+
+	/*
+	 * R2 onwards makes the count accessible to user mode so it can be used
+	 * by the VDSO (HWREna is configured by configure_hwrena()).
+	 */
+	if (cpu_has_mips_r2_r6 && rdhwr_count_usable())
+		clocksource_mips.archdata.vdso_clock_mode = VDSO_CLOCK_R4K;
+
+	clocksource_register_hz(&clocksource_mips, mips_hpt_frequency);
+
+#ifndef CONFIG_CPU_FREQ
+	sched_clock_register(r4k_read_sched_clock, 32, mips_hpt_frequency);
+#endif
+
+	return 0;
+}