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rtc: Add support for configuring the UIP timeout for RTC reads

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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: ec5895c0f2 ("rtc: mc146818-lib: extract mc146818_avoid_UIP")
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Tested-by: Mateusz Jończyk <mat.jonczyk@o2.pl>
Reviewed-by: Mateusz Jończyk <mat.jonczyk@o2.pl>
Acked-by: Mateusz Jończyk <mat.jonczyk@o2.pl>
Link: https://lore.kernel.org/r/20231128053653.101798-4-mario.limonciello@amd.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
This commit is contained in:
Mario Limonciello 2023-11-27 23:36:52 -06:00 committed by Alexandre Belloni
parent 1311a8f0d4
commit 120931db07
7 changed files with 38 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/alpha/kernel/rtc.c
View File

@ -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");

2
arch/x86/kernel/hpet.c
View File

@ -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;
}

2
arch/x86/kernel/rtc.c
View File

@ -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;

2
drivers/base/power/trace.c
View File

@ -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;
}

6
drivers/rtc/rtc-cmos.c
View File

@ -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);

37
drivers/rtc/rtc-mc146818-lib.c
View File

@ -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_LOOPS_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; UIP_RECHECK_LOOPS_MS(i) < 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 (UIP_RECHECK_LOOPS_MS(i) >= 100)
pr_warn("Reading current time from RTC took around %li ms\n",
UIP_RECHECK_LOOPS_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;
}

3
include/linux/mc146818rtc.h
View File

@ -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 */