[PATCH v3 0/4] ARM: at91: Properly handle slow clock

[PATCH v3 0/4] ARM: at91: Properly handle slow clock

[Alexandre Belloni]

Hi,

It was discovered that all the slow clock user were not properly claiming it.
This can end up in a system hang because the last registered user is releasing
it, and it gets disabled.

commit dca1a4b5ff6e ("clk: at91: keep slow clk enabled to prevent system hang")
was a workaround. This series is adding the slow clock to the necessary drivers
to avoid the issue and then removes that workaround.

Changes in v3:
 - dropped patches that were already taken or submitted separately
 - sclk is not a global anymore in timer-atmel-st.c
 - added Greg's ack

Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: linux-pwm at vger.kernel.org
Cc: linux-watchdog at vger.kernel.org
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wim Van Sebroeck <wim@iguana.be>

Alexandre Belloni (2):
  watchdog: at91sam9: get and use slow clock
  clocksource: atmel-st: get and use slow clock

Boris Brezillon (2):
  clocksource: tcb_clksrc: fix setup_clkevents error path
  misc: atmel_tclib: get and use slow clock

 drivers/clocksource/tcb_clksrc.c     | 10 +++++++++-
 drivers/clocksource/timer-atmel-st.c | 31 ++++++++++++++++++++++---------
 drivers/misc/atmel_tclib.c           |  4 ++++
 drivers/pwm/pwm-atmel-tcb.c          | 23 ++++++++++++++++-------
 drivers/watchdog/at91sam9_wdt.c      | 22 ++++++++++++++++++++--
 include/linux/atmel_tc.h             |  1 +
 6 files changed, 72 insertions(+), 19 deletions(-)

-- 
2.1.4

[PATCH v3 1/4] watchdog: at91sam9: get and use slow clock

[Alexandre Belloni]

Commit dca1a4b5ff6e ("clk: at91: keep slow clk enabled to prevent system
hang") added a workaround for the slow clock as it is not properly handled
by its users.

Get and use the slow clock as it is necessary for the at91sam9 watchdog.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
---
Cc: Wim Van Sebroeck <wim@iguana.be>
Cc: linux-watchdog at vger.kernel.org
 drivers/watchdog/at91sam9_wdt.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/watchdog/at91sam9_wdt.c b/drivers/watchdog/at91sam9_wdt.c
index e4698f7c5f93..7e6acaf3ece4 100644
--- a/drivers/watchdog/at91sam9_wdt.c
+++ b/drivers/watchdog/at91sam9_wdt.c
@@ -17,6 +17,7 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+#include <linux/clk.h>
 #include <linux/errno.h>
 #include <linux/init.h>
 #include <linux/interrupt.h>
@@ -90,6 +91,7 @@ struct at91wdt {
 	unsigned long heartbeat;	/* WDT heartbeat in jiffies */
 	bool nowayout;
 	unsigned int irq;
+	struct clk *sclk;
 };
 
 /* ......................................................................... */
@@ -352,15 +354,25 @@ static int __init at91wdt_probe(struct platform_device *pdev)
 	if (IS_ERR(wdt->base))
 		return PTR_ERR(wdt->base);
 
+	wdt->sclk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(wdt->sclk))
+		return PTR_ERR(wdt->sclk);
+
+	err = clk_prepare_enable(wdt->sclk);
+	if (err) {
+		dev_err(&pdev->dev, "Could not enable slow clock\n");
+		return err;
+	}
+
 	if (pdev->dev.of_node) {
 		err = of_at91wdt_init(pdev->dev.of_node, wdt);
 		if (err)
-			return err;
+			goto err_clk;
 	}
 
 	err = at91_wdt_init(pdev, wdt);
 	if (err)
-		return err;
+		goto err_clk;
 
 	platform_set_drvdata(pdev, wdt);
 
@@ -368,6 +380,11 @@ static int __init at91wdt_probe(struct platform_device *pdev)
 		wdt->wdd.timeout, wdt->nowayout);
 
 	return 0;
+
+err_clk:
+	clk_disable_unprepare(wdt->sclk);
+
+	return err;
 }
 
 static int __exit at91wdt_remove(struct platform_device *pdev)
@@ -377,6 +394,7 @@ static int __exit at91wdt_remove(struct platform_device *pdev)
 
 	pr_warn("I quit now, hardware will probably reboot!\n");
 	del_timer(&wdt->timer);
+	clk_disable_unprepare(wdt->sclk);
 
 	return 0;
 }
-- 
2.1.4

[PATCH v3 2/4] clocksource: atmel-st: get and use slow clock

[Alexandre Belloni]

The current slow clock rate is hardcoded. Properly get the slow clock
and use its rate.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
---
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
 drivers/clocksource/timer-atmel-st.c | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/drivers/clocksource/timer-atmel-st.c b/drivers/clocksource/timer-atmel-st.c
index 1692e17e096b..51dcbae0a654 100644
--- a/drivers/clocksource/timer-atmel-st.c
+++ b/drivers/clocksource/timer-atmel-st.c
@@ -22,6 +22,7 @@
 #include <linux/kernel.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
+#include <linux/clk.h>
 #include <linux/clockchips.h>
 #include <linux/export.h>
 #include <linux/mfd/syscon.h>
@@ -33,9 +34,7 @@ static unsigned long last_crtr;
 static u32 irqmask;
 static struct clock_event_device clkevt;
 static struct regmap *regmap_st;
-
-#define AT91_SLOW_CLOCK		32768
-#define RM9200_TIMER_LATCH	((AT91_SLOW_CLOCK + HZ/2) / HZ)
+static int timer_latch;
 
 /*
  * The ST_CRTR is updated asynchronously to the master clock ... but
@@ -82,8 +81,8 @@ static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id)
 	if (sr & AT91_ST_PITS) {
 		u32	crtr = read_CRTR();
 
-		while (((crtr - last_crtr) & AT91_ST_CRTV) >= RM9200_TIMER_LATCH) {
-			last_crtr += RM9200_TIMER_LATCH;
+		while (((crtr - last_crtr) & AT91_ST_CRTV) >= timer_latch) {
+			last_crtr += timer_latch;
 			clkevt.event_handler(&clkevt);
 		}
 		return IRQ_HANDLED;
@@ -120,7 +119,7 @@ clkevt32k_mode(enum clock_event_mode mode, struct clock_event_device *dev)
 	case CLOCK_EVT_MODE_PERIODIC:
 		/* PIT for periodic irqs; fixed rate of 1/HZ */
 		irqmask = AT91_ST_PITS;
-		regmap_write(regmap_st, AT91_ST_PIMR, RM9200_TIMER_LATCH);
+		regmap_write(regmap_st, AT91_ST_PIMR, timer_latch);
 		break;
 	case CLOCK_EVT_MODE_ONESHOT:
 		/* ALM for oneshot irqs, set by next_event()
@@ -182,7 +181,8 @@ static struct clock_event_device clkevt = {
  */
 static void __init atmel_st_timer_init(struct device_node *node)
 {
-	unsigned int val;
+	struct clk *sclk;
+	unsigned int sclk_rate, val;
 	int irq, ret;
 
 	regmap_st = syscon_node_to_regmap(node);
@@ -206,6 +206,19 @@ static void __init atmel_st_timer_init(struct device_node *node)
 	if (ret)
 		panic(pr_fmt("Unable to setup IRQ\n"));
 
+	sclk = of_clk_get(node, 0);
+	if (IS_ERR(sclk))
+		panic(pr_fmt("Unable to get slow clock\n"));
+
+	clk_prepare_enable(sclk);
+	if (ret)
+		panic(pr_fmt("Could not enable slow clock\n"));
+
+	sclk_rate = clk_get_rate(sclk);
+	if (!sclk_rate)
+		panic(pr_fmt("Invalid slow clock rate\n"));
+	timer_latch = (sclk_rate + HZ / 2) / HZ;
+
 	/* The 32KiHz "Slow Clock" (tick every 30517.58 nanoseconds) is used
 	 * directly for the clocksource and all clockevents, after adjusting
 	 * its prescaler from the 1 Hz default.
@@ -214,11 +227,11 @@ static void __init atmel_st_timer_init(struct device_node *node)
 
 	/* Setup timer clockevent, with minimum of two ticks (important!!) */
 	clkevt.cpumask = cpumask_of(0);
-	clockevents_config_and_register(&clkevt, AT91_SLOW_CLOCK,
+	clockevents_config_and_register(&clkevt, sclk_rate,
 					2, AT91_ST_ALMV);
 
 	/* register clocksource */
-	clocksource_register_hz(&clk32k, AT91_SLOW_CLOCK);
+	clocksource_register_hz(&clk32k, sclk_rate);
 }
 CLOCKSOURCE_OF_DECLARE(atmel_st_timer, "atmel,at91rm9200-st",
 		       atmel_st_timer_init);
-- 
2.1.4

[PATCH v3 2/4] clocksource: atmel-st: get and use slow clock

[Daniel Lezcano]

On 08/11/2015 11:38 AM, Alexandre Belloni wrote:
> The current slow clock rate is hardcoded. Properly get the slow clock
> and use its rate.
>
> Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>

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[PATCH v3 3/4] clocksource: tcb_clksrc: fix setup_clkevents error path

[Alexandre Belloni]

From: Boris Brezillon <boris.brezillon@free-electrons.com>

t2_clk is already disabled before request_irq(), it must not be disabled
again.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
---
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
 drivers/clocksource/tcb_clksrc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clocksource/tcb_clksrc.c b/drivers/clocksource/tcb_clksrc.c
index 8bdbc45c6dad..b9b7277173c2 100644
--- a/drivers/clocksource/tcb_clksrc.c
+++ b/drivers/clocksource/tcb_clksrc.c
@@ -199,7 +199,7 @@ static int __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
 
 	ret = request_irq(irq, ch2_irq, IRQF_TIMER, "tc_clkevt", &clkevt);
 	if (ret) {
-		clk_disable_unprepare(t2_clk);
+		clk_unprepare(t2_clk);
 		return ret;
 	}
 
-- 
2.1.4

[PATCH v3 3/4] clocksource: tcb_clksrc: fix setup_clkevents error path

[Daniel Lezcano]

On 08/11/2015 11:38 AM, Alexandre Belloni wrote:
> From: Boris Brezillon <boris.brezillon@free-electrons.com>
>
> t2_clk is already disabled before request_irq(), it must not be disabled
> again.
>
> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
> ---

Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>


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[PATCH v3 4/4] misc: atmel_tclib: get and use slow clock

[Alexandre Belloni]

From: Boris Brezillon <boris.brezillon@free-electrons.com>

Commit dca1a4b5ff6e ("clk: at91: keep slow clk enabled to prevent system
hang") added a workaround for the slow clock as it is not properly handled
by its users.

Get and use the slow clock as it is necessary for the timer counters.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: linux-pwm at vger.kernel.org

 drivers/clocksource/tcb_clksrc.c |  8 ++++++++
 drivers/misc/atmel_tclib.c       |  4 ++++
 drivers/pwm/pwm-atmel-tcb.c      | 23 ++++++++++++++++-------
 include/linux/atmel_tc.h         |  1 +
 4 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/drivers/clocksource/tcb_clksrc.c b/drivers/clocksource/tcb_clksrc.c
index b9b7277173c2..969ba03633b0 100644
--- a/drivers/clocksource/tcb_clksrc.c
+++ b/drivers/clocksource/tcb_clksrc.c
@@ -188,6 +188,13 @@ static int __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
 	ret = clk_prepare_enable(t2_clk);
 	if (ret)
 		return ret;
+
+	ret = clk_prepare_enable(tc->slow_clk);
+	if (ret) {
+		clk_disable_unprepare(t2_clk);
+		return ret;
+	}
+
 	clk_disable(t2_clk);
 
 	clkevt.regs = tc->regs;
@@ -200,6 +207,7 @@ static int __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
 	ret = request_irq(irq, ch2_irq, IRQF_TIMER, "tc_clkevt", &clkevt);
 	if (ret) {
 		clk_unprepare(t2_clk);
+		clk_disable_unprepare(tc->slow_clk);
 		return ret;
 	}
 
diff --git a/drivers/misc/atmel_tclib.c b/drivers/misc/atmel_tclib.c
index 0ca05c3ec8d6..ac24a4bd63f7 100644
--- a/drivers/misc/atmel_tclib.c
+++ b/drivers/misc/atmel_tclib.c
@@ -125,6 +125,10 @@ static int __init tc_probe(struct platform_device *pdev)
 	if (IS_ERR(clk))
 		return PTR_ERR(clk);
 
+	tc->slow_clk = devm_clk_get(&pdev->dev, "slow_clk");
+	if (IS_ERR(tc->slow_clk))
+		return PTR_ERR(tc->slow_clk);
+
 	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	tc->regs = devm_ioremap_resource(&pdev->dev, r);
 	if (IS_ERR(tc->regs))
diff --git a/drivers/pwm/pwm-atmel-tcb.c b/drivers/pwm/pwm-atmel-tcb.c
index d14e0677c92d..070a32a35295 100644
--- a/drivers/pwm/pwm-atmel-tcb.c
+++ b/drivers/pwm/pwm-atmel-tcb.c
@@ -305,7 +305,7 @@ static int atmel_tcb_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 	 */
 	if (i == 5) {
 		i = slowclk;
-		rate = 32768;
+		rate = clk_get_rate(tc->slow_clk);
 		min = div_u64(NSEC_PER_SEC, rate);
 		max = min << tc->tcb_config->counter_width;
 
@@ -387,9 +387,9 @@ static int atmel_tcb_pwm_probe(struct platform_device *pdev)
 
 	tcbpwm = devm_kzalloc(&pdev->dev, sizeof(*tcbpwm), GFP_KERNEL);
 	if (tcbpwm == NULL) {
-		atmel_tc_free(tc);
+		err = -ENOMEM;
 		dev_err(&pdev->dev, "failed to allocate memory\n");
-		return -ENOMEM;
+		goto err_free_tc;
 	}
 
 	tcbpwm->chip.dev = &pdev->dev;
@@ -400,17 +400,24 @@ static int atmel_tcb_pwm_probe(struct platform_device *pdev)
 	tcbpwm->chip.npwm = NPWM;
 	tcbpwm->tc = tc;
 
+	err = clk_prepare_enable(tc->slow_clk);
+	if (err)
+		goto err_free_tc;
+
 	spin_lock_init(&tcbpwm->lock);
 
 	err = pwmchip_add(&tcbpwm->chip);
-	if (err < 0) {
-		atmel_tc_free(tc);
-		return err;
-	}
+	if (err < 0)
+		goto err_free_tc;
 
 	platform_set_drvdata(pdev, tcbpwm);
 
 	return 0;
+
+err_free_tc:
+	atmel_tc_free(tc);
+
+	return err;
 }
 
 static int atmel_tcb_pwm_remove(struct platform_device *pdev)
@@ -418,6 +425,8 @@ static int atmel_tcb_pwm_remove(struct platform_device *pdev)
 	struct atmel_tcb_pwm_chip *tcbpwm = platform_get_drvdata(pdev);
 	int err;
 
+	clk_disable_unprepare(tcbpwm->tc->slow_clk);
+
 	err = pwmchip_remove(&tcbpwm->chip);
 	if (err < 0)
 		return err;
diff --git a/include/linux/atmel_tc.h b/include/linux/atmel_tc.h
index b87c1c7c242a..468fdfa643f0 100644
--- a/include/linux/atmel_tc.h
+++ b/include/linux/atmel_tc.h
@@ -67,6 +67,7 @@ struct atmel_tc {
 	const struct atmel_tcb_config *tcb_config;
 	int			irq[3];
 	struct clk		*clk[3];
+	struct clk		*slow_clk;
 	struct list_head	node;
 	bool			allocated;
 };
-- 
2.1.4

[PATCH v3 4/4] misc: atmel_tclib: get and use slow clock

[Daniel Lezcano]

On 08/11/2015 11:38 AM, Alexandre Belloni wrote:
> From: Boris Brezillon <boris.brezillon@free-electrons.com>
>
> Commit dca1a4b5ff6e ("clk: at91: keep slow clk enabled to prevent system
> hang") added a workaround for the slow clock as it is not properly handled
> by its users.
>
> Get and use the slow clock as it is necessary for the timer counters.
>
> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Thierry Reding <thierry.reding@gmail.com>
> Cc: linux-pwm at vger.kernel.org
>
>   drivers/clocksource/tcb_clksrc.c |  8 ++++++++
>   drivers/misc/atmel_tclib.c       |  4 ++++
>   drivers/pwm/pwm-atmel-tcb.c      | 23 ++++++++++++++++-------
>   include/linux/atmel_tc.h         |  1 +
>   4 files changed, 29 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/clocksource/tcb_clksrc.c b/drivers/clocksource/tcb_clksrc.c
> index b9b7277173c2..969ba03633b0 100644
> --- a/drivers/clocksource/tcb_clksrc.c
> +++ b/drivers/clocksource/tcb_clksrc.c
> @@ -188,6 +188,13 @@ static int __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
>   	ret = clk_prepare_enable(t2_clk);
>   	if (ret)
>   		return ret;
> +
> +	ret = clk_prepare_enable(tc->slow_clk);
> +	if (ret) {
> +		clk_disable_unprepare(t2_clk);
> +		return ret;
> +	}
> +
>   	clk_disable(t2_clk);

Do you need t2_clk to be enabled in order to enable tc->slow_clk ?

>   	clkevt.regs = tc->regs;
> @@ -200,6 +207,7 @@ static int __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
>   	ret = request_irq(irq, ch2_irq, IRQF_TIMER, "tc_clkevt", &clkevt);
>   	if (ret) {
>   		clk_unprepare(t2_clk);
> +		clk_disable_unprepare(tc->slow_clk);
>   		return ret;
>   	}
>
> diff --git a/drivers/misc/atmel_tclib.c b/drivers/misc/atmel_tclib.c
> index 0ca05c3ec8d6..ac24a4bd63f7 100644
> --- a/drivers/misc/atmel_tclib.c
> +++ b/drivers/misc/atmel_tclib.c

[ ... ]

> @@ -387,9 +387,9 @@ static int atmel_tcb_pwm_probe(struct platform_device *pdev)
>
>   	tcbpwm = devm_kzalloc(&pdev->dev, sizeof(*tcbpwm), GFP_KERNEL);
>   	if (tcbpwm == NULL) {
> -		atmel_tc_free(tc);
> +		err = -ENOMEM;
>   		dev_err(&pdev->dev, "failed to allocate memory\n");
> -		return -ENOMEM;
> +		goto err_free_tc;
>   	}
>
>   	tcbpwm->chip.dev = &pdev->dev;
> @@ -400,17 +400,24 @@ static int atmel_tcb_pwm_probe(struct platform_device *pdev)
>   	tcbpwm->chip.npwm = NPWM;
>   	tcbpwm->tc = tc;
>
> +	err = clk_prepare_enable(tc->slow_clk);
> +	if (err)
> +		goto err_free_tc;
> +
>   	spin_lock_init(&tcbpwm->lock);
>
>   	err = pwmchip_add(&tcbpwm->chip);
> -	if (err < 0) {
> -		atmel_tc_free(tc);
> -		return err;
> -	}
> +	if (err < 0)
> +		goto err_free_tc;
>
>   	platform_set_drvdata(pdev, tcbpwm);
>
>   	return 0;
> +
> +err_free_tc:
> +	atmel_tc_free(tc);
> +
> +	return err;

What about clk_unprepare_disable(tc->slow_clk) ?

>   }
>

[ ... ]


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[PATCH v3 4/4] misc: atmel_tclib: get and use slow clock

[Alexandre Belloni]

On 11/08/2015 at 15:40:45 +0200, Daniel Lezcano wrote :
> On 08/11/2015 11:38 AM, Alexandre Belloni wrote:
> >From: Boris Brezillon <boris.brezillon@free-electrons.com>
> >
> >Commit dca1a4b5ff6e ("clk: at91: keep slow clk enabled to prevent system
> >hang") added a workaround for the slow clock as it is not properly handled
> >by its users.
> >
> >Get and use the slow clock as it is necessary for the timer counters.
> >
> >Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> >Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
> >Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> >---
> >Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> >Cc: Thomas Gleixner <tglx@linutronix.de>
> >Cc: Thierry Reding <thierry.reding@gmail.com>
> >Cc: linux-pwm at vger.kernel.org
> >
> >  drivers/clocksource/tcb_clksrc.c |  8 ++++++++
> >  drivers/misc/atmel_tclib.c       |  4 ++++
> >  drivers/pwm/pwm-atmel-tcb.c      | 23 ++++++++++++++++-------
> >  include/linux/atmel_tc.h         |  1 +
> >  4 files changed, 29 insertions(+), 7 deletions(-)
> >
> >diff --git a/drivers/clocksource/tcb_clksrc.c b/drivers/clocksource/tcb_clksrc.c
> >index b9b7277173c2..969ba03633b0 100644
> >--- a/drivers/clocksource/tcb_clksrc.c
> >+++ b/drivers/clocksource/tcb_clksrc.c
> >@@ -188,6 +188,13 @@ static int __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
> >  	ret = clk_prepare_enable(t2_clk);
> >  	if (ret)
> >  		return ret;
> >+
> >+	ret = clk_prepare_enable(tc->slow_clk);
> >+	if (ret) {
> >+		clk_disable_unprepare(t2_clk);
> >+		return ret;
> >+	}
> >+
> >  	clk_disable(t2_clk);
> 
> Do you need t2_clk to be enabled in order to enable tc->slow_clk ?

No, I'll move clk_prepare_enable for tc->slow_clk before t2_clk.

> >+
> >+err_free_tc:
> >+	atmel_tc_free(tc);
> >+
> >+	return err;
> 
> What about clk_unprepare_disable(tc->slow_clk) ?
> 

Indeed, I trusted Boris a bit too much ;)

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com