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Message-Id: <20191106194625.116692-1-smuckle@google.com>
Date: Wed, 6 Nov 2019 11:46:25 -0800
From: Steve Muckle <smuckle@...gle.com>
To: Alessandro Zummo <a.zummo@...ertech.it>,
Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc: linux-kernel@...r.kernel.org, linux-rtc@...r.kernel.org,
kernel-team@...roid.com, Steve Muckle <smuckle@...gle.com>
Subject: [PATCH] rtc: class: support hctosys from modular RTC drivers
Due to distribution constraints it may not be possible to statically
compile the required RTC driver into the kernel.
Expand RTC_HCTOSYS support to cover all RTC devices (statically compiled
or not) by checking at the end of RTC device registration whether the
time should be synced.
Signed-off-by: Steve Muckle <smuckle@...gle.com>
---
drivers/rtc/Kconfig | 18 ++++++-----
drivers/rtc/Makefile | 1 -
drivers/rtc/class.c | 63 +++++++++++++++++++++++++++++++++++++++
drivers/rtc/hctosys.c | 69 -------------------------------------------
4 files changed, 73 insertions(+), 78 deletions(-)
delete mode 100644 drivers/rtc/hctosys.c
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 1adf9f815652..f663d77deb41 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -35,14 +35,16 @@ config RTC_HCTOSYS_DEVICE
depends on RTC_HCTOSYS
default "rtc0"
help
- The RTC device that will be used to (re)initialize the system
- clock, usually rtc0. Initialization is done when the system
- starts up, and when it resumes from a low power state. This
- device should record time in UTC, since the kernel won't do
- timezone correction.
-
- The driver for this RTC device must be loaded before late_initcall
- functions run, so it must usually be statically linked.
+ The RTC device that will be used to (re)initialize the system clock,
+ usually rtc0. Initialization is done when the driver for the RTC
+ device registers, and when it resumes from a low power state. This
+ device should record time in UTC, since the kernel won't do timezone
+ correction.
+
+ During startup it is useful to initialize the system clock from the
+ RTC as early as possible. For this reason the driver for this RTC
+ device should be statically linked, or alternately, the kernel module
+ for the RTC device driver loaded immediately.
This clock should be battery-backed, so that it reads the correct
time when the system boots from a power-off state. Otherwise, your
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 4ac8f19fb631..33f932d08262 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -6,7 +6,6 @@
ccflags-$(CONFIG_RTC_DEBUG) := -DDEBUG
obj-$(CONFIG_RTC_LIB) += lib.o
-obj-$(CONFIG_RTC_HCTOSYS) += hctosys.o
obj-$(CONFIG_RTC_SYSTOHC) += systohc.o
obj-$(CONFIG_RTC_CLASS) += rtc-core.o
obj-$(CONFIG_RTC_MC146818_LIB) += rtc-mc146818-lib.o
diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index 9458e6d6686a..b1ed5f3be223 100644
--- a/drivers/rtc/class.c
+++ b/drivers/rtc/class.c
@@ -34,6 +34,64 @@ 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 int rtc_hctosys(void)
+{
+ int err = -ENODEV;
+ struct rtc_time tm;
+ struct timespec64 tv64 = {
+ .tv_nsec = NSEC_PER_SEC >> 1,
+ };
+ struct rtc_device *rtc = rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE);
+
+ if (!rtc) {
+ pr_info("unable to open rtc device (%s)\n",
+ CONFIG_RTC_HCTOSYS_DEVICE);
+ goto err_open;
+ }
+
+ 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_class_close(rtc);
+
+err_open:
+ rtc_hctosys_ret = err;
+
+ return err;
+}
+
+
#endif
#if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
@@ -375,6 +433,11 @@ int __rtc_register_device(struct module *owner, struct rtc_device *rtc)
dev_info(rtc->dev.parent, "registered as %s\n",
dev_name(&rtc->dev));
+#ifdef CONFIG_RTC_HCTOSYS_DEVICE
+ if (!strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE))
+ rtc_hctosys();
+#endif
+
return 0;
}
EXPORT_SYMBOL_GPL(__rtc_register_device);
diff --git a/drivers/rtc/hctosys.c b/drivers/rtc/hctosys.c
deleted file mode 100644
index a74d0d890600..000000000000
--- a/drivers/rtc/hctosys.c
+++ /dev/null
@@ -1,69 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * RTC subsystem, initialize system time on startup
- *
- * Copyright (C) 2005 Tower Technologies
- * Author: Alessandro Zummo <a.zummo@...ertech.it>
- */
-
-#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
-
-#include <linux/rtc.h>
-
-/* 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 int __init rtc_hctosys(void)
-{
- int err = -ENODEV;
- struct rtc_time tm;
- struct timespec64 tv64 = {
- .tv_nsec = NSEC_PER_SEC >> 1,
- };
- struct rtc_device *rtc = rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE);
-
- if (!rtc) {
- pr_info("unable to open rtc device (%s)\n",
- CONFIG_RTC_HCTOSYS_DEVICE);
- goto err_open;
- }
-
- 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_class_close(rtc);
-
-err_open:
- rtc_hctosys_ret = err;
-
- return err;
-}
-
-late_initcall(rtc_hctosys);
--
2.24.0.rc1.363.gb1bccd3e3d-goog
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