[PATCH 3/4] rtc: Add support for configuring the UIP timeout for RTC reads
From: Mario Limonciello
Date: Fri Nov 17 2023 - 16:09:59 EST
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().
Make all callers use 10ms to ensure no functional changes.
Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
---
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 | 31 +++++++++++++++++++++++--------
include/linux/mc146818rtc.h | 3 ++-
7 files changed, 32 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 b39890a5531e..16dcbd196ce2 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..75b2fc1791e6 100644
--- a/drivers/rtc/rtc-mc146818-lib.c
+++ b/drivers/rtc/rtc-mc146818-lib.c
@@ -8,26 +8,29 @@
#include <linux/acpi.h>
#endif
+#define UIP_RECHECK_DELAY 100 /* usec */
+
/*
* 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 < USEC_PER_MSEC / UIP_RECHECK_DELAY * 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 +40,7 @@ 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 +59,7 @@ 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;
}
@@ -84,7 +87,7 @@ 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 +133,25 @@ 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 */
--
2.34.1