linux-kernel - [PATCH] clocksource: fix counter with 32bit may wrap around

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Date:   Fri, 31 Dec 2021 14:02:35 +0800
From:   weidong guan <weidong.guanguan@...il.com>
To:     daniel.lezcano@...aro.org
Cc:     tglx@...utronix.de, orsonzhai@...il.com, baolin.wang7@...il.com,
        zhang.lyra@...il.com, linux-kernel@...r.kernel.org,
        "weidong.guan" <weidong.guan@...soc.com>
Subject: [PATCH] clocksource: fix counter with 32bit may wrap around

From: "weidong.guan" <weidong.guan@...soc.com>

When the system sleep time exceeds 30+ hours, counter with 32bit may wrap
around, resulting in insufficient sleep compensation time. So We should
enable 64bit counter mode of sprd timer and use the given mult/shift
to ensure that sufficient counts can be generated.

Signed-off-by: weidong.guan <weidong.guan@...soc.com>
---
 drivers/clocksource/timer-sprd.c | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/drivers/clocksource/timer-sprd.c b/drivers/clocksource/timer-sprd.c
index 430cb99..7eac059 100644
--- a/drivers/clocksource/timer-sprd.c
+++ b/drivers/clocksource/timer-sprd.c
@@ -30,6 +30,7 @@
 #define TIMER_VALUE_SHDW_HI	0x1c
 
 #define TIMER_VALUE_LO_MASK	GENMASK(31, 0)
+#define TIMER_VALUE_64BIT_MASK GENMASK_ULL(63, 0)
 
 static void sprd_timer_enable(void __iomem *base, u32 flag)
 {
@@ -57,10 +58,12 @@ static void sprd_timer_disable(void __iomem *base)
 	writel_relaxed(val, base + TIMER_CTL);
 }
 
-static void sprd_timer_update_counter(void __iomem *base, unsigned long cycles)
+static void
+sprd_timer_update_counter(void __iomem *base, unsigned long long cycles)
 {
 	writel_relaxed(cycles & TIMER_VALUE_LO_MASK, base + TIMER_LOAD_LO);
-	writel_relaxed(0, base + TIMER_LOAD_HI);
+	writel_relaxed((cycles >> 32) & TIMER_VALUE_LO_MASK,
+			base + TIMER_LOAD_HI);
 }
 
 static void sprd_timer_enable_interrupt(void __iomem *base)
@@ -82,7 +85,7 @@ static int sprd_timer_set_next_event(unsigned long cycles,
 	struct timer_of *to = to_timer_of(ce);
 
 	sprd_timer_disable(timer_of_base(to));
-	sprd_timer_update_counter(timer_of_base(to), cycles);
+	sprd_timer_update_counter(timer_of_base(to), (u64)cycles);
 	sprd_timer_enable(timer_of_base(to), 0);
 
 	return 0;
@@ -93,7 +96,8 @@ static int sprd_timer_set_periodic(struct clock_event_device *ce)
 	struct timer_of *to = to_timer_of(ce);
 
 	sprd_timer_disable(timer_of_base(to));
-	sprd_timer_update_counter(timer_of_base(to), timer_of_period(to));
+	sprd_timer_update_counter(timer_of_base(to),
+				  (u64)timer_of_period(to));
 	sprd_timer_enable(timer_of_base(to), TIMER_CTL_PERIOD_MODE);
 
 	return 0;
@@ -162,15 +166,19 @@ static int __init sprd_timer_init(struct device_node *np)
 
 static u64 sprd_suspend_timer_read(struct clocksource *cs)
 {
-	return ~(u64)readl_relaxed(timer_of_base(&suspend_to) +
-				   TIMER_VALUE_SHDW_LO) & cs->mask;
+	u64 value_hi, value_lo;
+
+	value_hi = (u64)readl_relaxed(timer_of_base(&suspend_to) + TIMER_VALUE_SHDW_HI);
+	value_lo = (u64)readl_relaxed(timer_of_base(&suspend_to) + TIMER_VALUE_SHDW_LO);
+	return ~(u64)((value_hi << 32) + value_lo) & cs->mask;
 }
 
 static int sprd_suspend_timer_enable(struct clocksource *cs)
 {
 	sprd_timer_update_counter(timer_of_base(&suspend_to),
-				  TIMER_VALUE_LO_MASK);
-	sprd_timer_enable(timer_of_base(&suspend_to), TIMER_CTL_PERIOD_MODE);
+				  TIMER_VALUE_64BIT_MASK);
+	sprd_timer_enable(timer_of_base(&suspend_to),
+			  TIMER_CTL_PERIOD_MODE|TIMER_CTL_64BIT_WIDTH);
 
 	return 0;
 }
@@ -183,10 +191,12 @@ static void sprd_suspend_timer_disable(struct clocksource *cs)
 static struct clocksource suspend_clocksource = {
 	.name	= "sprd_suspend_timer",
 	.rating	= 200,
+	.mult   = 0x1DCD650,
+	.shift  = 10,
 	.read	= sprd_suspend_timer_read,
 	.enable = sprd_suspend_timer_enable,
 	.disable = sprd_suspend_timer_disable,
-	.mask	= CLOCKSOURCE_MASK(32),
+	.mask	= CLOCKSOURCE_MASK(64),
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS | CLOCK_SOURCE_SUSPEND_NONSTOP,
 };
 
@@ -198,8 +208,7 @@ static int __init sprd_suspend_timer_init(struct device_node *np)
 	if (ret)
 		return ret;
 
-	clocksource_register_hz(&suspend_clocksource,
-				timer_of_rate(&suspend_to));
+	clocksource_register_hz(&suspend_clocksource, 0);
 
 	return 0;
 }
-- 
1.9.1