v4.19.13 snapshot.
diff --git a/arch/mips/kernel/csrc-ioasic.c b/arch/mips/kernel/csrc-ioasic.c
new file mode 100644
index 0000000..f6acd1e
--- /dev/null
+++ b/arch/mips/kernel/csrc-ioasic.c
@@ -0,0 +1,74 @@
+/*
+ * DEC I/O ASIC's counter clocksource
+ *
+ * Copyright (C) 2008 Yoichi Yuasa <yuasa@linux-mips.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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/clocksource.h>
+#include <linux/sched_clock.h>
+#include <linux/init.h>
+
+#include <asm/ds1287.h>
+#include <asm/time.h>
+#include <asm/dec/ioasic.h>
+#include <asm/dec/ioasic_addrs.h>
+
+static u64 dec_ioasic_hpt_read(struct clocksource *cs)
+{
+ return ioasic_read(IO_REG_FCTR);
+}
+
+static struct clocksource clocksource_dec = {
+ .name = "dec-ioasic",
+ .read = dec_ioasic_hpt_read,
+ .mask = CLOCKSOURCE_MASK(32),
+ .flags = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static u64 notrace dec_ioasic_read_sched_clock(void)
+{
+ return ioasic_read(IO_REG_FCTR);
+}
+
+int __init dec_ioasic_clocksource_init(void)
+{
+ unsigned int freq;
+ u32 start, end;
+ int i = HZ / 8;
+
+ ds1287_timer_state();
+ while (!ds1287_timer_state())
+ ;
+
+ start = dec_ioasic_hpt_read(&clocksource_dec);
+
+ while (i--)
+ while (!ds1287_timer_state())
+ ;
+
+ end = dec_ioasic_hpt_read(&clocksource_dec);
+
+ freq = (end - start) * 8;
+
+ /* An early revision of the I/O ASIC didn't have the counter. */
+ if (!freq)
+ return -ENXIO;
+
+ printk(KERN_INFO "I/O ASIC clock frequency %dHz\n", freq);
+
+ clocksource_dec.rating = 200 + freq / 10000000;
+ clocksource_register_hz(&clocksource_dec, freq);
+
+ sched_clock_register(dec_ioasic_read_sched_clock, 32, freq);
+
+ return 0;
+}