Commit 0dd8d6cb authored by Mateusz Jończyk's avatar Mateusz Jończyk Committed by Alexandre Belloni
Browse files

rtc: Check return value from mc146818_get_time() 



There are 4 users of mc146818_get_time() and none of them was checking
the return value from this function. Change this.

Print the appropriate warnings in callers of mc146818_get_time() instead
of in the function mc146818_get_time() itself, in order not to add
strings to rtc-mc146818-lib.c, which is kind of a library.

The callers of alpha_rtc_read_time() and cmos_read_time() may use the
contents of (struct rtc_time *) even when the functions return a failure
code. Therefore, set the contents of (struct rtc_time *) to 0x00,
which looks more sensible then 0xff and aligns with the (possibly
stale?) comment in cmos_read_time:

	/*
	 * If pm_trace abused the RTC for storage, set the timespec to 0,
	 * which tells the caller that this RTC value is unusable.
	 */

For consistency, do this in mc146818_get_time().

Note: hpet_rtc_interrupt() may call mc146818_get_time() many times a
second. It is very unlikely, though, that the RTC suddenly stops
working and mc146818_get_time() would consistently fail.

Only compile-tested on alpha.

Signed-off-by: default avatarMateusz Jończyk <mat.jonczyk@o2.pl>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: linux-alpha@vger.kernel.org
Cc: x86@kernel.org
Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20211210200131.153887-4-mat.jonczyk@o2.pl
parent d35786b3

arch/alpha/kernel/rtc.c

+6 −1
Original line number Diff line number Diff line
@@ -80,7 +80,12 @@ init_rtc_epoch(void) 
static int

alpha_rtc_read_time(struct device *dev, struct rtc_time *tm)

{

	mc146818_get_time(tm);

	int ret = mc146818_get_time(tm);



	if (ret < 0) {

		dev_err_ratelimited(dev, "unable to read current time\n");

		return ret;

	}



	/* Adjust for non-default epochs.  It's easier to depend on the

	   generic __get_rtc_time and adjust the epoch here than create

arch/x86/kernel/hpet.c

+6 −2
Original line number Diff line number Diff line
@@ -1435,8 +1435,12 @@ irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id) 
	hpet_rtc_timer_reinit();

	memset(&curr_time, 0, sizeof(struct rtc_time));



	if (hpet_rtc_flags & (RTC_UIE | RTC_AIE))

		mc146818_get_time(&curr_time);

	if (hpet_rtc_flags & (RTC_UIE | RTC_AIE)) {

		if (unlikely(mc146818_get_time(&curr_time) < 0)) {

			pr_err_ratelimited("unable to read current time from RTC\n");

			return IRQ_HANDLED;

		}

	}



	if (hpet_rtc_flags & RTC_UIE &&

	    curr_time.tm_sec != hpet_prev_update_sec) {

drivers/base/power/trace.c

+5 −1
Original line number Diff line number Diff line
@@ -120,7 +120,11 @@ static unsigned int read_magic_time(void) 
	struct rtc_time time;

	unsigned int val;



	mc146818_get_time(&time);

	if (mc146818_get_time(&time) < 0) {

		pr_err("Unable to read current time from RTC\n");

		return 0;

	}



	pr_info("RTC time: %ptRt, date: %ptRd\n", &time, &time);

	val = time.tm_year;				/* 100 years */

	if (val > 100)

drivers/rtc/rtc-cmos.c

+8 −1
Original line number Diff line number Diff line
@@ -222,6 +222,8 @@ static inline void cmos_write_bank2(unsigned char val, unsigned char addr) 


static int cmos_read_time(struct device *dev, struct rtc_time *t)

{

	int ret;



	/*

	 * If pm_trace abused the RTC for storage, set the timespec to 0,

	 * which tells the caller that this RTC value is unusable.
@@ -229,7 +231,12 @@ static int cmos_read_time(struct device *dev, struct rtc_time *t) 
	if (!pm_trace_rtc_valid())

		return -EIO;



	mc146818_get_time(t);

	ret = mc146818_get_time(t);

	if (ret < 0) {

		dev_err_ratelimited(dev, "unable to read current time\n");

		return ret;

	}



	return 0;

}

drivers/rtc/rtc-mc146818-lib.c

+1 −1
Original line number Diff line number Diff line
@@ -24,7 +24,7 @@ unsigned int mc146818_get_time(struct rtc_time *time) 
	/* Ensure that the RTC is accessible. Bit 6 must be 0! */

	if (WARN_ON_ONCE((CMOS_READ(RTC_VALID) & 0x40) != 0)) {

		spin_unlock_irqrestore(&rtc_lock, flags);

		memset(time, 0xff, sizeof(*time));

		memset(time, 0, sizeof(*time));

		return -EIO;

	}