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

[kernel test robot <lkp@intel.com>]

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	

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