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(-)
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 */
--
2.34.1Hi 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
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
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
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
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
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
>
>
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