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@xxxxxxxxxxxxxxx # 6.1.y
> Fixes: ec5895c0f2d8 ("rtc: mc146818-lib: extract mc146818_avoid_UIP")
> Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> ---
> 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
