diff mbox series

[3/6] rtc: brcmstb-waketimer: compensate for lack of wktmr disable

Message ID 20230120190147.718976-4-opendmb@gmail.com
State New
Headers
Series rtc: brcmstb-waketimer: add RTC alarm irq |

Commit Message

Doug Berger Jan. 20, 2023, 7:01 p.m. UTC 
  Since the WKTMR hardware block cannot be disabled it is necessary
for the driver to accommodate for associated timing hazards. This
commit targets the following possibilities:

A possible race between clearing a wktmr event and the alarm expiring
is made one-sided by setting the alarm to its maximum value before
clearing the event.

Programming alarm values close to the current time may not trigger
events if the counter advances while the alarm is being programmed.
After programming an alarm, a check is made to ensure that it is
either in the future or an expiration event is pending.

Signed-off-by: Doug Berger <opendmb@gmail.com>
---
 drivers/rtc/rtc-brcmstb-waketimer.c | 52 +++++++++++++++++++----------
 1 file changed, 34 insertions(+), 18 deletions(-)

Comments

Florian Fainelli Jan. 23, 2023, 7:21 p.m. UTC | #1 
On 1/20/23 11:01, Doug Berger wrote:
> Since the WKTMR hardware block cannot be disabled it is necessary
> for the driver to accommodate for associated timing hazards. This
> commit targets the following possibilities:
> 
> A possible race between clearing a wktmr event and the alarm expiring
> is made one-sided by setting the alarm to its maximum value before
> clearing the event.
> 
> Programming alarm values close to the current time may not trigger
> events if the counter advances while the alarm is being programmed.
> After programming an alarm, a check is made to ensure that it is
> either in the future or an expiration event is pending.
> 
> Signed-off-by: Doug Berger <opendmb@gmail.com>

Acked-by: Florian Fainelli <f.fainelli@gmail.com>
diff mbox series

Patch

diff --git a/drivers/rtc/rtc-brcmstb-waketimer.c b/drivers/rtc/rtc-brcmstb-waketimer.c
index 582c23793550..c791e92532b8 100644
--- a/drivers/rtc/rtc-brcmstb-waketimer.c
+++ b/drivers/rtc/rtc-brcmstb-waketimer.c
@@ -31,6 +31,8 @@  struct brcmstb_waketmr {
 	struct notifier_block reboot_notifier;
 	struct clk *clk;
 	u32 rate;
+	unsigned long rtc_alarm;
+	bool alarm_en;
 };
 
 #define BRCMSTB_WKTMR_EVENT		0x00
@@ -52,6 +54,11 @@  static inline bool brcmstb_waketmr_is_pending(struct brcmstb_waketmr *timer)
 
 static inline void brcmstb_waketmr_clear_alarm(struct brcmstb_waketmr *timer)
 {
+	u32 reg;
+
+	timer->alarm_en = false;
+	reg = readl_relaxed(timer->base + BRCMSTB_WKTMR_COUNTER);
+	writel_relaxed(reg - 1, timer->base + BRCMSTB_WKTMR_ALARM);
 	writel_relaxed(WKTMR_ALARM_EVENT, timer->base + BRCMSTB_WKTMR_EVENT);
 	(void)readl_relaxed(timer->base + BRCMSTB_WKTMR_EVENT);
 }
@@ -59,12 +66,22 @@  static inline void brcmstb_waketmr_clear_alarm(struct brcmstb_waketmr *timer)
 static void brcmstb_waketmr_set_alarm(struct brcmstb_waketmr *timer,
 				      unsigned int secs)
 {
+	unsigned int now;
+
 	brcmstb_waketmr_clear_alarm(timer);
 
 	/* Make sure we are actually counting in seconds */
 	writel_relaxed(timer->rate, timer->base + BRCMSTB_WKTMR_PRESCALER);
 
-	writel_relaxed(secs + 1, timer->base + BRCMSTB_WKTMR_ALARM);
+	writel_relaxed(secs, timer->base + BRCMSTB_WKTMR_ALARM);
+	now = readl_relaxed(timer->base + BRCMSTB_WKTMR_COUNTER);
+
+	while ((int)(secs - now) <= 0 &&
+		!brcmstb_waketmr_is_pending(timer)) {
+		secs = now + 1;
+		writel_relaxed(secs, timer->base + BRCMSTB_WKTMR_ALARM);
+		now = readl_relaxed(timer->base + BRCMSTB_WKTMR_COUNTER);
+	}
 }
 
 static irqreturn_t brcmstb_waketmr_irq(int irq, void *data)
@@ -155,27 +172,30 @@  static int brcmstb_waketmr_getalarm(struct device *dev,
 				    struct rtc_wkalrm *alarm)
 {
 	struct brcmstb_waketmr *timer = dev_get_drvdata(dev);
-	time64_t sec;
 
-	sec = readl_relaxed(timer->base + BRCMSTB_WKTMR_ALARM);
-	if (sec != 0) {
-		/* Alarm is enabled */
-		alarm->enabled = 1;
-		rtc_time64_to_tm(sec, &alarm->time);
-	}
+	alarm->enabled = timer->alarm_en;
+	rtc_time64_to_tm(timer->rtc_alarm, &alarm->time);
 
 	alarm->pending = brcmstb_waketmr_is_pending(timer);
 
 	return 0;
 }
 
-/*
- * Does not do much but keep the RTC class happy. We always support
- * alarms.
- */
 static int brcmstb_waketmr_alarm_enable(struct device *dev,
 					unsigned int enabled)
 {
+	struct brcmstb_waketmr *timer = dev_get_drvdata(dev);
+
+	if (enabled && !timer->alarm_en) {
+		if ((int)(readl_relaxed(timer->base + BRCMSTB_WKTMR_COUNTER) -
+		    readl_relaxed(timer->base + BRCMSTB_WKTMR_ALARM)) >= 0 &&
+		    !brcmstb_waketmr_is_pending(timer))
+			return -EINVAL;
+		timer->alarm_en = true;
+	} else if (!enabled && timer->alarm_en) {
+		timer->alarm_en = false;
+	}
+
 	return 0;
 }
 
@@ -183,14 +203,10 @@  static int brcmstb_waketmr_setalarm(struct device *dev,
 				     struct rtc_wkalrm *alarm)
 {
 	struct brcmstb_waketmr *timer = dev_get_drvdata(dev);
-	time64_t sec;
 
-	if (alarm->enabled)
-		sec = rtc_tm_to_time64(&alarm->time);
-	else
-		sec = 0;
+	timer->rtc_alarm = rtc_tm_to_time64(&alarm->time);
 
-	brcmstb_waketmr_set_alarm(timer, sec);
+	brcmstb_waketmr_set_alarm(timer, timer->rtc_alarm);
 
 	return brcmstb_waketmr_alarm_enable(dev, alarm->enabled);
 }