Commit f9b2a4d6 authored by Steve Muckle's avatar Steve Muckle Committed by Alexandre Belloni
Browse files

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: default avatarSteve Muckle <smuckle@google.com>
Link: https://lore.kernel.org/r/20191106194625.116692-1-smuckle@google.com


Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@bootlin.com>
parent 34ce2977

drivers/rtc/Kconfig

+0 −3
Original line number Diff line number Diff line
@@ -41,9 +41,6 @@ config RTC_HCTOSYS_DEVICE 
	  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.



	  This clock should be battery-backed, so that it reads the correct

	  time when the system boots from a power-off state. Otherwise, your

	  system will need an external clock source (like an NTP server).

drivers/rtc/Makefile

+0 −1
Original line number Diff line number Diff line
@@ -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

drivers/rtc/class.c

+61 −0
Original line number Diff line number Diff line
@@ -34,6 +34,62 @@ 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 +431,11 @@ 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);

drivers/rtc/hctosys.c

deleted100644 → 0
+0 −69
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/*

 * RTC subsystem, initialize system time on startup

 *

 * Copyright (C) 2005 Tower Technologies

 * Author: Alessandro Zummo <a.zummo@towertech.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);

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