diff mbox series

[v3,3/4] rtc: Add support for configuring the UIP timeout for RTC reads

Message ID 20231127192553.9734-4-mario.limonciello@amd.com (mailing list archive)
State Superseded, archived
Headers show
Series Extend time to wait for UIP for some callers | expand

Commit Message

Mario Limonciello Nov. 27, 2023, 7:25 p.m. UTC
The UIP timeout is hardcoded to 10ms for all RTC reads, but in some
contexts this might not be enough time. Add a timeout parameter to
mc146818_get_time() and mc146818_get_time_callback().

If UIP timeout is configured by caller to be >=100 ms and a call
takes this long, log a warning.

Make all callers use 10ms to ensure no functional changes.

Cc: stable@vger.kernel.org # 6.1.y
Fixes: ec5895c0f2d8 ("rtc: mc146818-lib: extract mc146818_avoid_UIP")
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
v2->v3:
 * Logic adjustments
 * Clarify warning message
v1->v2:
 * Add a warning if 100ms or more
 * Add stable and fixes tags
---
 arch/alpha/kernel/rtc.c        |  2 +-
 arch/x86/kernel/hpet.c         |  2 +-
 arch/x86/kernel/rtc.c          |  2 +-
 drivers/base/power/trace.c     |  2 +-
 drivers/rtc/rtc-cmos.c         |  6 +++---
 drivers/rtc/rtc-mc146818-lib.c | 37 ++++++++++++++++++++++++++--------
 include/linux/mc146818rtc.h    |  3 ++-
 7 files changed, 38 insertions(+), 16 deletions(-)

Comments

Mateusz Jończyk Nov. 27, 2023, 8:31 p.m. UTC | #1
W dniu 27.11.2023 o 20:25, Mario Limonciello pisze:
> The UIP timeout is hardcoded to 10ms for all RTC reads, but in some
> contexts this might not be enough time. Add a timeout parameter to
> mc146818_get_time() and mc146818_get_time_callback().
>
> If UIP timeout is configured by caller to be >=100 ms and a call
> takes this long, log a warning.
>
> Make all callers use 10ms to ensure no functional changes.
>
> Cc: stable@vger.kernel.org # 6.1.y
> Fixes: ec5895c0f2d8 ("rtc: mc146818-lib: extract mc146818_avoid_UIP")
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
> v2->v3:
>  * Logic adjustments
>  * Clarify warning message
> v1->v2:
>  * Add a warning if 100ms or more
>  * Add stable and fixes tags
[snip]
> diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c
> index 43a28e82674e..ab077dde397b 100644
> --- a/drivers/rtc/rtc-mc146818-lib.c
> +++ b/drivers/rtc/rtc-mc146818-lib.c
> @@ -8,26 +8,31 @@
>  #include <linux/acpi.h>
>  #endif
>  
> +#define UIP_RECHECK_DELAY		100	/* usec */
> +#define UIP_RECHECK_DELAY_MS		(USEC_PER_MSEC / UIP_RECHECK_DELAY)
> +#define UIP_RECHECK_TIMEOUT_MS(x)	(x / UIP_RECHECK_DELAY_MS)
> +
>  /*
>   * Execute a function while the UIP (Update-in-progress) bit of the RTC is
> - * unset.
> + * unset. The timeout is configurable by the caller in ms.
>   *
>   * Warning: callback may be executed more then once.
>   */
>  bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
> +			int timeout,
>  			void *param)
>  {
>  	int i;
>  	unsigned long flags;
>  	unsigned char seconds;
>  
> -	for (i = 0; i < 100; i++) {
> +	for (i = 0; i < UIP_RECHECK_TIMEOUT_MS(timeout); i++) {

Sorry, this will not work. UIP_RECHECK_DELAY_MS is 10, so
UIP_RECHECK_TIMEOUT_MS(timeout) will be 1 for timeout=10. Should be

      for (i = 0; UIP_RECHECK_TIMEOUT_MS(i) < timeout; i++) {

With this, for i == 99, UIP_RECHECK_TIMEOUT_MS(i) = 9
for i == 100, UIP_RECHECK_TIMEOUT_MS(i) = 10 and the loop correctly terminates.

The macro should probably be renamed UIP_RECHECK_LOOPS_MS as it converts
loop count to ms.

>  		spin_lock_irqsave(&rtc_lock, flags);
>  
>  		/*
>  		 * Check whether there is an update in progress during which the
>  		 * readout is unspecified. The maximum update time is ~2ms. Poll
> -		 * every 100 usec for completion.
> +		 * for completion.
>  		 *
>  		 * Store the second value before checking UIP so a long lasting
>  		 * NMI which happens to hit after the UIP check cannot make
> @@ -37,7 +42,7 @@ bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
>  
>  		if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
>  			spin_unlock_irqrestore(&rtc_lock, flags);
> -			udelay(100);
> +			udelay(UIP_RECHECK_DELAY);
>  			continue;
>  		}
>  
> @@ -56,7 +61,7 @@ bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
>  		 */
>  		if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
>  			spin_unlock_irqrestore(&rtc_lock, flags);
> -			udelay(100);
> +			udelay(UIP_RECHECK_DELAY);
>  			continue;
>  		}
>  
> @@ -72,6 +77,10 @@ bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
>  		}
>  		spin_unlock_irqrestore(&rtc_lock, flags);
>  
> +		if (i >= UIP_RECHECK_TIMEOUT_MS(100))

Same, should be:

          if (UIP_RECHECK_TIMEOUT_MS(i) >= 100)

> +			pr_warn("Reading current time from RTC took around %d ms\n",
> +				UIP_RECHECK_TIMEOUT_MS(i));
> +
>  		return true;
>  	}
>  	return false;

[snip]

Greetings,

Mateusz
Mario Limonciello Nov. 27, 2023, 8:37 p.m. UTC | #2
On 11/27/2023 14:31, Mateusz Jończyk wrote:
> W dniu 27.11.2023 o 20:25, Mario Limonciello pisze:
>> The UIP timeout is hardcoded to 10ms for all RTC reads, but in some
>> contexts this might not be enough time. Add a timeout parameter to
>> mc146818_get_time() and mc146818_get_time_callback().
>>
>> If UIP timeout is configured by caller to be >=100 ms and a call
>> takes this long, log a warning.
>>
>> Make all callers use 10ms to ensure no functional changes.
>>
>> Cc: stable@vger.kernel.org # 6.1.y
>> Fixes: ec5895c0f2d8 ("rtc: mc146818-lib: extract mc146818_avoid_UIP")
>> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
>> ---
>> v2->v3:
>>   * Logic adjustments
>>   * Clarify warning message
>> v1->v2:
>>   * Add a warning if 100ms or more
>>   * Add stable and fixes tags
> [snip]
>> diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c
>> index 43a28e82674e..ab077dde397b 100644
>> --- a/drivers/rtc/rtc-mc146818-lib.c
>> +++ b/drivers/rtc/rtc-mc146818-lib.c
>> @@ -8,26 +8,31 @@
>>   #include <linux/acpi.h>
>>   #endif
>>   
>> +#define UIP_RECHECK_DELAY		100	/* usec */
>> +#define UIP_RECHECK_DELAY_MS		(USEC_PER_MSEC / UIP_RECHECK_DELAY)
>> +#define UIP_RECHECK_TIMEOUT_MS(x)	(x / UIP_RECHECK_DELAY_MS)
>> +
>>   /*
>>    * Execute a function while the UIP (Update-in-progress) bit of the RTC is
>> - * unset.
>> + * unset. The timeout is configurable by the caller in ms.
>>    *
>>    * Warning: callback may be executed more then once.
>>    */
>>   bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
>> +			int timeout,
>>   			void *param)
>>   {
>>   	int i;
>>   	unsigned long flags;
>>   	unsigned char seconds;
>>   
>> -	for (i = 0; i < 100; i++) {
>> +	for (i = 0; i < UIP_RECHECK_TIMEOUT_MS(timeout); i++) {
> 
> Sorry, this will not work. UIP_RECHECK_DELAY_MS is 10, so
> UIP_RECHECK_TIMEOUT_MS(timeout) will be 1 for timeout=10. Should be
> 
>        for (i = 0; UIP_RECHECK_TIMEOUT_MS(i) < timeout; i++) {
> 
> With this, for i == 99, UIP_RECHECK_TIMEOUT_MS(i) = 9
> for i == 100, UIP_RECHECK_TIMEOUT_MS(i) = 10 and the loop correctly terminates.
> 
> The macro should probably be renamed UIP_RECHECK_LOOPS_MS as it converts
> loop count to ms.

Got it; thanks for that.

> 
>>   		spin_lock_irqsave(&rtc_lock, flags);
>>   
>>   		/*
>>   		 * Check whether there is an update in progress during which the
>>   		 * readout is unspecified. The maximum update time is ~2ms. Poll
>> -		 * every 100 usec for completion.
>> +		 * for completion.
>>   		 *
>>   		 * Store the second value before checking UIP so a long lasting
>>   		 * NMI which happens to hit after the UIP check cannot make
>> @@ -37,7 +42,7 @@ bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
>>   
>>   		if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
>>   			spin_unlock_irqrestore(&rtc_lock, flags);
>> -			udelay(100);
>> +			udelay(UIP_RECHECK_DELAY);
>>   			continue;
>>   		}
>>   
>> @@ -56,7 +61,7 @@ bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
>>   		 */
>>   		if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
>>   			spin_unlock_irqrestore(&rtc_lock, flags);
>> -			udelay(100);
>> +			udelay(UIP_RECHECK_DELAY);
>>   			continue;
>>   		}
>>   
>> @@ -72,6 +77,10 @@ bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
>>   		}
>>   		spin_unlock_irqrestore(&rtc_lock, flags);
>>   
>> +		if (i >= UIP_RECHECK_TIMEOUT_MS(100))
> 
> Same, should be:
> 
>            if (UIP_RECHECK_TIMEOUT_MS(i) >= 100)
> 
>> +			pr_warn("Reading current time from RTC took around %d ms\n",
>> +				UIP_RECHECK_TIMEOUT_MS(i));
>> +
>>   		return true;
>>   	}
>>   	return false;
> 
> [snip]
> 
> Greetings,
> 
> Mateusz
> 
>
kernel test robot Nov. 28, 2023, 12:19 a.m. UTC | #3
Hi Mario,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 2cc14f52aeb78ce3f29677c2de1f06c0e91471ab]

url:    https://github.com/intel-lab-lkp/linux/commits/Mario-Limonciello/rtc-mc146818-lib-Adjust-failure-return-code-for-mc146818_get_time/20231128-032825
base:   2cc14f52aeb78ce3f29677c2de1f06c0e91471ab
patch link:    https://lore.kernel.org/r/20231127192553.9734-4-mario.limonciello%40amd.com
patch subject: [PATCH v3 3/4] rtc: Add support for configuring the UIP timeout for RTC reads
config: alpha-defconfig (https://download.01.org/0day-ci/archive/20231128/202311280605.EB8LQAVD-lkp@intel.com/config)
compiler: alpha-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231128/202311280605.EB8LQAVD-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202311280605.EB8LQAVD-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from include/asm-generic/bug.h:22,
                    from arch/alpha/include/asm/bug.h:23,
                    from include/linux/bug.h:5,
                    from include/linux/thread_info.h:13,
                    from include/asm-generic/current.h:6,
                    from ./arch/alpha/include/generated/asm/current.h:1,
                    from include/linux/sched.h:12,
                    from include/linux/delay.h:23,
                    from drivers/rtc/rtc-mc146818-lib.c:3:
   drivers/rtc/rtc-mc146818-lib.c: In function 'mc146818_avoid_UIP':
>> include/linux/kern_levels.h:5:25: warning: format '%d' expects argument of type 'int', but argument 2 has type 'long int' [-Wformat=]
       5 | #define KERN_SOH        "\001"          /* ASCII Start Of Header */
         |                         ^~~~~~
   include/linux/printk.h:427:25: note: in definition of macro 'printk_index_wrap'
     427 |                 _p_func(_fmt, ##__VA_ARGS__);                           \
         |                         ^~~~
   include/linux/printk.h:508:9: note: in expansion of macro 'printk'
     508 |         printk(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__)
         |         ^~~~~~
   include/linux/kern_levels.h:12:25: note: in expansion of macro 'KERN_SOH'
      12 | #define KERN_WARNING    KERN_SOH "4"    /* warning conditions */
         |                         ^~~~~~~~
   include/linux/printk.h:508:16: note: in expansion of macro 'KERN_WARNING'
     508 |         printk(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__)
         |                ^~~~~~~~~~~~
   drivers/rtc/rtc-mc146818-lib.c:81:25: note: in expansion of macro 'pr_warn'
      81 |                         pr_warn("Reading current time from RTC took around %d ms\n",
         |                         ^~~~~~~


vim +5 include/linux/kern_levels.h

314ba3520e513a Joe Perches 2012-07-30  4  
04d2c8c83d0e3a Joe Perches 2012-07-30 @5  #define KERN_SOH	"\001"		/* ASCII Start Of Header */
04d2c8c83d0e3a Joe Perches 2012-07-30  6  #define KERN_SOH_ASCII	'\001'
04d2c8c83d0e3a Joe Perches 2012-07-30  7
kernel test robot Nov. 28, 2023, 3:01 a.m. UTC | #4
Hi Mario,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 2cc14f52aeb78ce3f29677c2de1f06c0e91471ab]

url:    https://github.com/intel-lab-lkp/linux/commits/Mario-Limonciello/rtc-mc146818-lib-Adjust-failure-return-code-for-mc146818_get_time/20231128-032825
base:   2cc14f52aeb78ce3f29677c2de1f06c0e91471ab
patch link:    https://lore.kernel.org/r/20231127192553.9734-4-mario.limonciello%40amd.com
patch subject: [PATCH v3 3/4] rtc: Add support for configuring the UIP timeout for RTC reads
config: i386-randconfig-141-20231128 (https://download.01.org/0day-ci/archive/20231128/202311280845.YrtuJ0eq-lkp@intel.com/config)
compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231128/202311280845.YrtuJ0eq-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202311280845.YrtuJ0eq-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/rtc/rtc-mc146818-lib.c:82:5: warning: format specifies type 'int' but the argument has type 'long' [-Wformat]
                                   UIP_RECHECK_TIMEOUT_MS(i));
                                   ^~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/printk.h:508:37: note: expanded from macro 'pr_warn'
           printk(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__)
                                      ~~~     ^~~~~~~~~~~
   include/linux/printk.h:455:60: note: expanded from macro 'printk'
   #define printk(fmt, ...) printk_index_wrap(_printk, fmt, ##__VA_ARGS__)
                                                       ~~~    ^~~~~~~~~~~
   include/linux/printk.h:427:19: note: expanded from macro 'printk_index_wrap'
                   _p_func(_fmt, ##__VA_ARGS__);                           \
                           ~~~~    ^~~~~~~~~~~
   drivers/rtc/rtc-mc146818-lib.c:13:35: note: expanded from macro 'UIP_RECHECK_TIMEOUT_MS'
   #define UIP_RECHECK_TIMEOUT_MS(x)       (x / UIP_RECHECK_DELAY_MS)
                                           ^~~~~~~~~~~~~~~~~~~~~~~~~~
   1 warning generated.


vim +82 drivers/rtc/rtc-mc146818-lib.c

    14	
    15	/*
    16	 * Execute a function while the UIP (Update-in-progress) bit of the RTC is
    17	 * unset. The timeout is configurable by the caller in ms.
    18	 *
    19	 * Warning: callback may be executed more then once.
    20	 */
    21	bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
    22				int timeout,
    23				void *param)
    24	{
    25		int i;
    26		unsigned long flags;
    27		unsigned char seconds;
    28	
    29		for (i = 0; i < UIP_RECHECK_TIMEOUT_MS(timeout); i++) {
    30			spin_lock_irqsave(&rtc_lock, flags);
    31	
    32			/*
    33			 * Check whether there is an update in progress during which the
    34			 * readout is unspecified. The maximum update time is ~2ms. Poll
    35			 * for completion.
    36			 *
    37			 * Store the second value before checking UIP so a long lasting
    38			 * NMI which happens to hit after the UIP check cannot make
    39			 * an update cycle invisible.
    40			 */
    41			seconds = CMOS_READ(RTC_SECONDS);
    42	
    43			if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
    44				spin_unlock_irqrestore(&rtc_lock, flags);
    45				udelay(UIP_RECHECK_DELAY);
    46				continue;
    47			}
    48	
    49			/* Revalidate the above readout */
    50			if (seconds != CMOS_READ(RTC_SECONDS)) {
    51				spin_unlock_irqrestore(&rtc_lock, flags);
    52				continue;
    53			}
    54	
    55			if (callback)
    56				callback(seconds, param);
    57	
    58			/*
    59			 * Check for the UIP bit again. If it is set now then
    60			 * the above values may contain garbage.
    61			 */
    62			if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
    63				spin_unlock_irqrestore(&rtc_lock, flags);
    64				udelay(UIP_RECHECK_DELAY);
    65				continue;
    66			}
    67	
    68			/*
    69			 * A NMI might have interrupted the above sequence so check
    70			 * whether the seconds value has changed which indicates that
    71			 * the NMI took longer than the UIP bit was set. Unlikely, but
    72			 * possible and there is also virt...
    73			 */
    74			if (seconds != CMOS_READ(RTC_SECONDS)) {
    75				spin_unlock_irqrestore(&rtc_lock, flags);
    76				continue;
    77			}
    78			spin_unlock_irqrestore(&rtc_lock, flags);
    79	
    80			if (i >= UIP_RECHECK_TIMEOUT_MS(100))
    81				pr_warn("Reading current time from RTC took around %d ms\n",
  > 82					UIP_RECHECK_TIMEOUT_MS(i));
    83	
    84			return true;
    85		}
    86		return false;
    87	}
    88	EXPORT_SYMBOL_GPL(mc146818_avoid_UIP);
    89
diff mbox series

Patch

diff --git a/arch/alpha/kernel/rtc.c b/arch/alpha/kernel/rtc.c
index fb3025396ac9..cfdf90bc8b3f 100644
--- a/arch/alpha/kernel/rtc.c
+++ b/arch/alpha/kernel/rtc.c
@@ -80,7 +80,7 @@  init_rtc_epoch(void)
 static int
 alpha_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
-	int ret = mc146818_get_time(tm);
+	int ret = mc146818_get_time(tm, 10);
 
 	if (ret < 0) {
 		dev_err_ratelimited(dev, "unable to read current time\n");
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index 41eecf180b7f..17adad4cbe78 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -1438,7 +1438,7 @@  irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id)
 	memset(&curr_time, 0, sizeof(struct rtc_time));
 
 	if (hpet_rtc_flags & (RTC_UIE | RTC_AIE)) {
-		if (unlikely(mc146818_get_time(&curr_time) < 0)) {
+		if (unlikely(mc146818_get_time(&curr_time, 10) < 0)) {
 			pr_err_ratelimited("unable to read current time from RTC\n");
 			return IRQ_HANDLED;
 		}
diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index 1309b9b05338..961ebc7f1872 100644
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -67,7 +67,7 @@  void mach_get_cmos_time(struct timespec64 *now)
 		return;
 	}
 
-	if (mc146818_get_time(&tm)) {
+	if (mc146818_get_time(&tm, 10)) {
 		pr_err("Unable to read current time from RTC\n");
 		now->tv_sec = now->tv_nsec = 0;
 		return;
diff --git a/drivers/base/power/trace.c b/drivers/base/power/trace.c
index 72b7a92337b1..c2e925357474 100644
--- a/drivers/base/power/trace.c
+++ b/drivers/base/power/trace.c
@@ -120,7 +120,7 @@  static unsigned int read_magic_time(void)
 	struct rtc_time time;
 	unsigned int val;
 
-	if (mc146818_get_time(&time) < 0) {
+	if (mc146818_get_time(&time, 10) < 0) {
 		pr_err("Unable to read current time from RTC\n");
 		return 0;
 	}
diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index 391f91d3d144..d278b085821e 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -231,7 +231,7 @@  static int cmos_read_time(struct device *dev, struct rtc_time *t)
 	if (!pm_trace_rtc_valid())
 		return -EIO;
 
-	ret = mc146818_get_time(t);
+	ret = mc146818_get_time(t, 10);
 	if (ret < 0) {
 		dev_err_ratelimited(dev, "unable to read current time\n");
 		return ret;
@@ -307,7 +307,7 @@  static int cmos_read_alarm(struct device *dev, struct rtc_wkalrm *t)
 	 *
 	 * Use the mc146818_avoid_UIP() function to avoid this.
 	 */
-	if (!mc146818_avoid_UIP(cmos_read_alarm_callback, &p))
+	if (!mc146818_avoid_UIP(cmos_read_alarm_callback, 10, &p))
 		return -EIO;
 
 	if (!(p.rtc_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
@@ -556,7 +556,7 @@  static int cmos_set_alarm(struct device *dev, struct rtc_wkalrm *t)
 	 *
 	 * Use mc146818_avoid_UIP() to avoid this.
 	 */
-	if (!mc146818_avoid_UIP(cmos_set_alarm_callback, &p))
+	if (!mc146818_avoid_UIP(cmos_set_alarm_callback, 10, &p))
 		return -ETIMEDOUT;
 
 	cmos->alarm_expires = rtc_tm_to_time64(&t->time);
diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c
index 43a28e82674e..ab077dde397b 100644
--- a/drivers/rtc/rtc-mc146818-lib.c
+++ b/drivers/rtc/rtc-mc146818-lib.c
@@ -8,26 +8,31 @@ 
 #include <linux/acpi.h>
 #endif
 
+#define UIP_RECHECK_DELAY		100	/* usec */
+#define UIP_RECHECK_DELAY_MS		(USEC_PER_MSEC / UIP_RECHECK_DELAY)
+#define UIP_RECHECK_TIMEOUT_MS(x)	(x / UIP_RECHECK_DELAY_MS)
+
 /*
  * Execute a function while the UIP (Update-in-progress) bit of the RTC is
- * unset.
+ * unset. The timeout is configurable by the caller in ms.
  *
  * Warning: callback may be executed more then once.
  */
 bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
+			int timeout,
 			void *param)
 {
 	int i;
 	unsigned long flags;
 	unsigned char seconds;
 
-	for (i = 0; i < 100; i++) {
+	for (i = 0; i < UIP_RECHECK_TIMEOUT_MS(timeout); i++) {
 		spin_lock_irqsave(&rtc_lock, flags);
 
 		/*
 		 * Check whether there is an update in progress during which the
 		 * readout is unspecified. The maximum update time is ~2ms. Poll
-		 * every 100 usec for completion.
+		 * for completion.
 		 *
 		 * Store the second value before checking UIP so a long lasting
 		 * NMI which happens to hit after the UIP check cannot make
@@ -37,7 +42,7 @@  bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
 
 		if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
 			spin_unlock_irqrestore(&rtc_lock, flags);
-			udelay(100);
+			udelay(UIP_RECHECK_DELAY);
 			continue;
 		}
 
@@ -56,7 +61,7 @@  bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
 		 */
 		if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
 			spin_unlock_irqrestore(&rtc_lock, flags);
-			udelay(100);
+			udelay(UIP_RECHECK_DELAY);
 			continue;
 		}
 
@@ -72,6 +77,10 @@  bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
 		}
 		spin_unlock_irqrestore(&rtc_lock, flags);
 
+		if (i >= UIP_RECHECK_TIMEOUT_MS(100))
+			pr_warn("Reading current time from RTC took around %d ms\n",
+				UIP_RECHECK_TIMEOUT_MS(i));
+
 		return true;
 	}
 	return false;
@@ -84,7 +93,7 @@  EXPORT_SYMBOL_GPL(mc146818_avoid_UIP);
  */
 bool mc146818_does_rtc_work(void)
 {
-	return mc146818_avoid_UIP(NULL, NULL);
+	return mc146818_avoid_UIP(NULL, 10, NULL);
 }
 EXPORT_SYMBOL_GPL(mc146818_does_rtc_work);
 
@@ -130,13 +139,25 @@  static void mc146818_get_time_callback(unsigned char seconds, void *param_in)
 	p->ctrl = CMOS_READ(RTC_CONTROL);
 }
 
-int mc146818_get_time(struct rtc_time *time)
+/**
+ * mc146818_get_time - Get the current time from the RTC
+ * @time: pointer to struct rtc_time to store the current time
+ * @timeout: timeout value in ms
+ *
+ * This function reads the current time from the RTC and stores it in the
+ * provided struct rtc_time. The timeout parameter specifies the maximum
+ * time to wait for the RTC to become ready.
+ *
+ * Return: 0 on success, -ETIMEDOUT if the RTC did not become ready within
+ * the specified timeout, or another error code if an error occurred.
+ */
+int mc146818_get_time(struct rtc_time *time, int timeout)
 {
 	struct mc146818_get_time_callback_param p = {
 		.time = time
 	};
 
-	if (!mc146818_avoid_UIP(mc146818_get_time_callback, &p)) {
+	if (!mc146818_avoid_UIP(mc146818_get_time_callback, timeout, &p)) {
 		memset(time, 0, sizeof(*time));
 		return -ETIMEDOUT;
 	}
diff --git a/include/linux/mc146818rtc.h b/include/linux/mc146818rtc.h
index b0da04fe087b..34dfcc77f505 100644
--- a/include/linux/mc146818rtc.h
+++ b/include/linux/mc146818rtc.h
@@ -126,10 +126,11 @@  struct cmos_rtc_board_info {
 #endif /* ARCH_RTC_LOCATION */
 
 bool mc146818_does_rtc_work(void);
-int mc146818_get_time(struct rtc_time *time);
+int mc146818_get_time(struct rtc_time *time, int timeout);
 int mc146818_set_time(struct rtc_time *time);
 
 bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
+			int timeout,
 			void *param);
 
 #endif /* _MC146818RTC_H */