rtc: Check return value from mc146818_get_time()

[ Upstream commit 0dd8d6cb9eddfe637bcd821bbfd40ebd5a0737b9 ]

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: Mateusz 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: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20211210200131.153887-4-mat.jonczyk@o2.pl
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/alpha/kernel/rtc.c b/arch/alpha/kernel/rtc.c
index ce30779..fb30253 100644 (file)
--- a/arch/alpha/kernel/rtc.c
+++ b/arch/alpha/kernel/rtc.c
@@ -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

diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index 882213d..71f3364 100644 (file)
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -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) {

diff --git a/drivers/base/power/trace.c b/drivers/base/power/trace.c
index 9466503..72b7a92 100644 (file)
--- a/drivers/base/power/trace.c
+++ b/drivers/base/power/trace.c
@@ -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)

diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index dc3f8b0..d0f58cc 100644 (file)
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -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;
 }
 

diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c
index bd48cee..97e3ceb 100644 (file)
--- a/drivers/rtc/rtc-mc146818-lib.c
+++ b/drivers/rtc/rtc-mc146818-lib.c
@@ -24,7 +24,7 @@ again:
        /* 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;
        }