v4.19.13 snapshot.
diff --git a/drivers/clocksource/tango_xtal.c b/drivers/clocksource/tango_xtal.c
new file mode 100644
index 0000000..3f94e45
--- /dev/null
+++ b/drivers/clocksource/tango_xtal.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/clocksource.h>
+#include <linux/sched_clock.h>
+#include <linux/of_address.h>
+#include <linux/printk.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/clk.h>
+
+static void __iomem *xtal_in_cnt;
+static struct delay_timer delay_timer;
+
+static unsigned long notrace read_xtal_counter(void)
+{
+ return readl_relaxed(xtal_in_cnt);
+}
+
+static u64 notrace read_sched_clock(void)
+{
+ return read_xtal_counter();
+}
+
+static int __init tango_clocksource_init(struct device_node *np)
+{
+ struct clk *clk;
+ int xtal_freq, ret;
+
+ xtal_in_cnt = of_iomap(np, 0);
+ if (xtal_in_cnt == NULL) {
+ pr_err("%pOF: invalid address\n", np);
+ return -ENXIO;
+ }
+
+ clk = of_clk_get(np, 0);
+ if (IS_ERR(clk)) {
+ pr_err("%pOF: invalid clock\n", np);
+ return PTR_ERR(clk);
+ }
+
+ xtal_freq = clk_get_rate(clk);
+ delay_timer.freq = xtal_freq;
+ delay_timer.read_current_timer = read_xtal_counter;
+
+ ret = clocksource_mmio_init(xtal_in_cnt, "tango-xtal", xtal_freq, 350,
+ 32, clocksource_mmio_readl_up);
+ if (ret) {
+ pr_err("%pOF: registration failed\n", np);
+ return ret;
+ }
+
+ sched_clock_register(read_sched_clock, 32, xtal_freq);
+ register_current_timer_delay(&delay_timer);
+
+ return 0;
+}
+
+TIMER_OF_DECLARE(tango, "sigma,tick-counter", tango_clocksource_init);