From 0fb885c7b70916f111bdde57a96b607604a14bb2 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@google.com>
Date: Thu, 9 Apr 2020 15:28:26 +0200
Subject: [PATCH] ANDROID: fix up rtc-core merge error in previous upstream
 merge

Commit dd5c9369672e ("Merge 7e63420847ae ("Merge tag 'acpi-5.7-rc1-2' of
git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm") into
android-mainline") was not done properly, and had a half-completed merge
of drivers/rtc/class.c

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ibedf4e800ef54c77da371dea24fede7adc8a4a37
---
 drivers/rtc/class.c    | 46 +++++++++++++++++++++++++++++++++++++++++-
 drivers/rtc/rtc-core.h |  4 ----
 2 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index 970b19c0fead..7c88d190c51f 100644
--- a/drivers/rtc/class.c
+++ b/drivers/rtc/class.c
@@ -34,6 +34,50 @@ static void rtc_device_release(struct device *dev)
 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
 /* Result of the last RTC to system clock attempt. */
 int rtc_hctosys_ret = -ENODEV;
+
+/* IMPORTANT: the RTC only stores whole seconds. It is arbitrary
+ * whether it stores the most close value or the value with partial
+ * seconds truncated. However, it is important that we use it to store
+ * the truncated value. This is because otherwise it is necessary,
+ * in an rtc sync function, to read both xtime.tv_sec and
+ * xtime.tv_nsec. On some processors (i.e. ARM), an atomic read
+ * of >32bits is not possible. So storing the most close value would
+ * slow down the sync API. So here we have the truncated value and
+ * the best guess is to add 0.5s.
+ */
+
+static void rtc_hctosys(struct rtc_device *rtc)
+{
+	int err;
+	struct rtc_time tm;
+	struct timespec64 tv64 = {
+		.tv_nsec = NSEC_PER_SEC >> 1,
+	};
+
+	err = rtc_read_time(rtc, &tm);
+	if (err) {
+		dev_err(rtc->dev.parent,
+			"hctosys: unable to read the hardware clock\n");
+		goto err_read;
+	}
+
+	tv64.tv_sec = rtc_tm_to_time64(&tm);
+
+#if BITS_PER_LONG == 32
+	if (tv64.tv_sec > INT_MAX) {
+		err = -ERANGE;
+		goto err_read;
+	}
+#endif
+
+	err = do_settimeofday64(&tv64);
+
+	dev_info(rtc->dev.parent, "setting system clock to %ptR UTC (%lld)\n",
+		 &tm, (long long)tv64.tv_sec);
+
+err_read:
+	rtc_hctosys_ret = err;
+}
 #endif
 
 #if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
@@ -377,7 +421,7 @@ int __rtc_register_device(struct module *owner, struct rtc_device *rtc)
 
 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
 	if (!strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE))
-		rtc_hctosys();
+		rtc_hctosys(rtc);
 #endif
 
 	return 0;
diff --git a/drivers/rtc/rtc-core.h b/drivers/rtc/rtc-core.h
index c38ef33a4bff..0abf98983e13 100644
--- a/drivers/rtc/rtc-core.h
+++ b/drivers/rtc/rtc-core.h
@@ -46,7 +46,3 @@ static inline const struct attribute_group **rtc_get_dev_attribute_groups(void)
 	return NULL;
 }
 #endif
-
-#ifdef CONFIG_RTC_HCTOSYS
-extern int rtc_hctosys(void);
-#endif