v4.19.13 snapshot.
diff --git a/arch/powerpc/kernel/rtas-rtc.c b/arch/powerpc/kernel/rtas-rtc.c
new file mode 100644
index 0000000..a28239b
--- /dev/null
+++ b/arch/powerpc/kernel/rtas-rtc.c
@@ -0,0 +1,113 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/time.h>
+#include <linux/timer.h>
+#include <linux/init.h>
+#include <linux/rtc.h>
+#include <linux/delay.h>
+#include <linux/ratelimit.h>
+#include <asm/prom.h>
+#include <asm/rtas.h>
+#include <asm/time.h>
+
+
+#define MAX_RTC_WAIT 5000 /* 5 sec */
+#define RTAS_CLOCK_BUSY (-2)
+time64_t __init rtas_get_boot_time(void)
+{
+ int ret[8];
+ int error;
+ unsigned int wait_time;
+ u64 max_wait_tb;
+
+ max_wait_tb = get_tb() + tb_ticks_per_usec * 1000 * MAX_RTC_WAIT;
+ do {
+ error = rtas_call(rtas_token("get-time-of-day"), 0, 8, ret);
+
+ wait_time = rtas_busy_delay_time(error);
+ if (wait_time) {
+ /* This is boot time so we spin. */
+ udelay(wait_time*1000);
+ }
+ } while (wait_time && (get_tb() < max_wait_tb));
+
+ if (error != 0) {
+ printk_ratelimited(KERN_WARNING
+ "error: reading the clock failed (%d)\n",
+ error);
+ return 0;
+ }
+
+ return mktime64(ret[0], ret[1], ret[2], ret[3], ret[4], ret[5]);
+}
+
+/* NOTE: get_rtc_time will get an error if executed in interrupt context
+ * and if a delay is needed to read the clock. In this case we just
+ * silently return without updating rtc_tm.
+ */
+void rtas_get_rtc_time(struct rtc_time *rtc_tm)
+{
+ int ret[8];
+ int error;
+ unsigned int wait_time;
+ u64 max_wait_tb;
+
+ max_wait_tb = get_tb() + tb_ticks_per_usec * 1000 * MAX_RTC_WAIT;
+ do {
+ error = rtas_call(rtas_token("get-time-of-day"), 0, 8, ret);
+
+ wait_time = rtas_busy_delay_time(error);
+ if (wait_time) {
+ if (in_interrupt()) {
+ memset(rtc_tm, 0, sizeof(struct rtc_time));
+ printk_ratelimited(KERN_WARNING
+ "error: reading clock "
+ "would delay interrupt\n");
+ return; /* delay not allowed */
+ }
+ msleep(wait_time);
+ }
+ } while (wait_time && (get_tb() < max_wait_tb));
+
+ if (error != 0) {
+ printk_ratelimited(KERN_WARNING
+ "error: reading the clock failed (%d)\n",
+ error);
+ return;
+ }
+
+ rtc_tm->tm_sec = ret[5];
+ rtc_tm->tm_min = ret[4];
+ rtc_tm->tm_hour = ret[3];
+ rtc_tm->tm_mday = ret[2];
+ rtc_tm->tm_mon = ret[1] - 1;
+ rtc_tm->tm_year = ret[0] - 1900;
+}
+
+int rtas_set_rtc_time(struct rtc_time *tm)
+{
+ int error, wait_time;
+ u64 max_wait_tb;
+
+ max_wait_tb = get_tb() + tb_ticks_per_usec * 1000 * MAX_RTC_WAIT;
+ do {
+ error = rtas_call(rtas_token("set-time-of-day"), 7, 1, NULL,
+ tm->tm_year + 1900, tm->tm_mon + 1,
+ tm->tm_mday, tm->tm_hour, tm->tm_min,
+ tm->tm_sec, 0);
+
+ wait_time = rtas_busy_delay_time(error);
+ if (wait_time) {
+ if (in_interrupt())
+ return 1; /* probably decrementer */
+ msleep(wait_time);
+ }
+ } while (wait_time && (get_tb() < max_wait_tb));
+
+ if (error != 0)
+ printk_ratelimited(KERN_WARNING
+ "error: setting the clock failed (%d)\n",
+ error);
+
+ return 0;
+}