clockevents/clocksource fixes for 4.8-rc3

Hi Thomas, Ingo,

this is the second round of fixes for 4.8-rc3.

- Add the mck clock enablement for the ETM/ETB driver (Alexandre Belloni)

- Clear the interrupts after stopping the timer in order to prevent
spurious interrupt at init time (Chen-Yu Tsai)

- Fix a memory corruption on pistachio by replacing a reference to
pointer by the pointer itself (Marcin Nowakowski)

Thanks !

-- Daniel

The following changes since commit aa8c0f1ad7e862147f4efb32bbb71ff66eb38caa:

clocksource/drivers/pxa: Fix include files for compilation (2016-08-24
11:16:38 +0200)

are available in the git repository at:

http://git.linaro.org/people/daniel.lezcano/linux.git
clockevents/4.8-fixes

for you to fetch changes up to b53e7d000d9e6e9fd2c6eb6b82d2783c67fd599e:

clocksource/drivers/sun4i: Clear interrupts after stopping timer in
probe function (2016-08-26 15:56:01 +0200)

----------------------------------------------------------------
Alexandre Belloni (1):
clocksource/drivers/timer-atmel-pit: Enable mck clock

Chen-Yu Tsai (1):
clocksource/drivers/sun4i: Clear interrupts after stopping timer
in probe function

Marcin Nowakowski (1):
drivers/clocksource/pistachio: Fix memory corruption in init

 drivers/clocksource/sun4i_timer.c     | 9 ++++++++-
 drivers/clocksource/time-pistachio.c  | 8 ++++----
 drivers/clocksource/timer-atmel-pit.c | 6 ++++++
 3 files changed, 18 insertions(+), 5 deletions(-)

 <http://www.linaro.org/> Linaro.org ? Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog

From: Alexandre Belloni <[email protected]>

mck is needed to get the PIT working. Explicitly prepare_enable it instead of assuming it is enabled.

This solves an issue where the system is freezing when the ETM/ETB drivers are enabled.

---
 drivers/clocksource/timer-atmel-pit.c | 6 ++++++
 1 file changed, 6 insertions(+)

index 1ffac0c..3494bc5 100644
@@ -261,6 +261,12 @@ static int __init at91sam926x_pit_dt_init(struct device_node *node)
 		return PTR_ERR(data->mck);
 	}
 
+	ret = clk_prepare_enable(data->mck);
+	if (ret) {
+		pr_err("Unable to enable mck\n");
+		return ret;
+	}
+
 	/* Get the interrupts property */
 	data->irq = irq_of_parse_and_map(node, 0);
 	if (!data->irq) {

1.9.1

From: Marcin Nowakowski <[email protected]>

Driver init code incorrectly uses the block base address and as a result clears clocksource structure's fields instead of the hardware registers.

Commit 09a998201649 ("timekeeping: Lift clocksource cacheline restriction") has changed the offsets within pistachio_clocksource structure and what has previously gone unnoticed now leads to a kernel panic during boot.

---
 drivers/clocksource/time-pistachio.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

index a7d9a08..a8e6c7d 100644
@@ -202,10 +202,10 @@ static int __init pistachio_clksrc_of_init(struct device_node *node)
 	rate = clk_get_rate(fast_clk);
 
 	/* Disable irq's for clocksource usage */
-	gpt_writel(&pcs_gpt.base, 0, TIMER_IRQ_MASK, 0);
-	gpt_writel(&pcs_gpt.base, 0, TIMER_IRQ_MASK, 1);
-	gpt_writel(&pcs_gpt.base, 0, TIMER_IRQ_MASK, 2);
-	gpt_writel(&pcs_gpt.base, 0, TIMER_IRQ_MASK, 3);
+	gpt_writel(pcs_gpt.base, 0, TIMER_IRQ_MASK, 0);
+	gpt_writel(pcs_gpt.base, 0, TIMER_IRQ_MASK, 1);
+	gpt_writel(pcs_gpt.base, 0, TIMER_IRQ_MASK, 2);
+	gpt_writel(pcs_gpt.base, 0, TIMER_IRQ_MASK, 3);
 
 	/* Enable timer block */
 	writel(TIMER_ME_GLOBAL, pcs_gpt.base);

1.9.1

From: Chen-Yu Tsai <[email protected]>

The bootloader (U-boot) sometimes uses this timer for various delays. It uses it as a ongoing counter, and does comparisons on the current counter value. The timer counter is never stopped.

In some cases when the user interacts with the bootloader, or lets it idle for some time before loading Linux, the timer may expire, and an interrupt will be pending. This results in an unexpected interrupt when the timer interrupt is enabled by the kernel, at which point the event_handler isn't set yet. This results in a NULL pointer dereference exception, panic, and no way to reboot.

Clear any pending interrupts after we stop the timer in the probe function to avoid this.

---
 drivers/clocksource/sun4i_timer.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

index 97669ee..c83452c 100644
@@ -123,12 +123,16 @@ static struct clock_event_device sun4i_clockevent = {
 	.set_next_event = sun4i_clkevt_next_event,
 };
 
+static void sun4i_timer_clear_interrupt(void)
+{
+	writel(TIMER_IRQ_EN(0), timer_base + TIMER_IRQ_ST_REG);
+}
 
 static irqreturn_t sun4i_timer_interrupt(int irq, void *dev_id)
 {
 	struct clock_event_device *evt = (struct clock_event_device *)dev_id;
 
-	writel(0x1, timer_base + TIMER_IRQ_ST_REG);
+	sun4i_timer_clear_interrupt();
 	evt->event_handler(evt);
 
 	return IRQ_HANDLED;

@@ -208,6 +212,9 @@ static int __init sun4i_timer_init(struct device_node *node)
 	/* Make sure timer is stopped before playing with interrupts */
 	sun4i_clkevt_time_stop(0);
 
+	/* clear timer0 interrupt */
+	sun4i_timer_clear_interrupt();
+
 	sun4i_clockevent.cpumask = cpu_possible_mask;
 	sun4i_clockevent.irq = irq;
 

1.9.1

Hi,

index 3494bc5..7f0f5b2 100644
@@ -240,6 +240,7 @@ static int __init at91sam926x_pit_common_init(struct pit_data *data)
 static int __init at91sam926x_pit_dt_init(struct device_node *node)
 {
        struct pit_data *data;
+       int ret;
 
        data = kzalloc(sizeof(*data), GFP_KERNEL);
        if (!data)

Hi Mark,

It is fixed.

https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git/commit/?h=timers/urgent&id=98744b408c757901df57fa50cbd5826245dc3a1f

Thanks for reporting the issue and for the fix.

-- Daniel

 <http://www.linaro.org/> Linaro.org ? Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog