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[PATCH v8 1/3] clocksource/drivers/timer-tegra186: add WDIOC_GETTIMELEFT support

Robert Lin posted 3 patches 7 months, 1 week ago
[PATCH v8 1/3] clocksource/drivers/timer-tegra186: add WDIOC_GETTIMELEFT support
Posted by Robert Lin 7 months, 1 week ago 
From: Pohsun Su <pohsuns@nvidia.com>

This change adds support for WDIOC_GETTIMELEFT so userspace
programs can get the number of seconds before system reset by
the watchdog timer via ioctl.

Signed-off-by: Pohsun Su <pohsuns@nvidia.com>
Signed-off-by: Robert Lin <robelin@nvidia.com>
---
 drivers/clocksource/timer-tegra186.c | 64 +++++++++++++++++++++++++++-
 1 file changed, 63 insertions(+), 1 deletion(-)

diff --git a/drivers/clocksource/timer-tegra186.c b/drivers/clocksource/timer-tegra186.c
index ea742889ee06..e3ea6110e6f5 100644
--- a/drivers/clocksource/timer-tegra186.c
+++ b/drivers/clocksource/timer-tegra186.c
@@ -1,8 +1,9 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /*
- * Copyright (c) 2019-2020 NVIDIA Corporation. All rights reserved.
+ * Copyright (c) 2019-2025 NVIDIA Corporation. All rights reserved.
  */
 
+#include <linux/bitfield.h>
 #include <linux/clocksource.h>
 #include <linux/module.h>
 #include <linux/interrupt.h>
@@ -30,6 +31,7 @@
 
 #define TMRSR 0x004
 #define  TMRSR_INTR_CLR BIT(30)
+#define  TMRSR_PCV GENMASK(28, 0)
 
 #define TMRCSSR 0x008
 #define  TMRCSSR_SRC_USEC (0 << 0)
@@ -46,6 +48,9 @@
 #define  WDTCR_TIMER_SOURCE_MASK 0xf
 #define  WDTCR_TIMER_SOURCE(x) ((x) & 0xf)
 
+#define WDTSR 0x004
+#define  WDTSR_CURRENT_EXPIRATION_COUNT GENMASK(14, 12)
+
 #define WDTCMDR 0x008
 #define  WDTCMDR_DISABLE_COUNTER BIT(1)
 #define  WDTCMDR_START_COUNTER BIT(0)
@@ -235,12 +240,69 @@ static int tegra186_wdt_set_timeout(struct watchdog_device *wdd,
 	return 0;
 }
 
+static unsigned int tegra186_wdt_get_timeleft(struct watchdog_device *wdd)
+{
+	struct tegra186_wdt *wdt = to_tegra186_wdt(wdd);
+	u32 expiration, val;
+	u64 timeleft;
+
+	if (!watchdog_active(&wdt->base)) {
+		/* return zero if the watchdog timer is not activated. */
+		return 0;
+	}
+
+	/*
+	 * Reset occurs on the fifth expiration of the
+	 * watchdog timer and so when the watchdog timer is configured,
+	 * the actual value programmed into the counter is 1/5 of the
+	 * timeout value. Once the counter reaches 0, expiration count
+	 * will be increased by 1 and the down counter restarts.
+	 * Hence to get the time left before system reset we must
+	 * combine 2 parts:
+	 * 1. value of the current down counter
+	 * 2. (number of counter expirations remaining) * (timeout/5)
+	 */
+
+	/* Get the current number of counter expirations. Should be a
+	 * value between 0 and 4
+	 */
+	val = readl_relaxed(wdt->regs + WDTSR);
+	expiration = FIELD_GET(WDTSR_CURRENT_EXPIRATION_COUNT, val);
+	if (WARN_ON_ONCE(expiration > 4))
+		return 0;
+
+	/* Get the current counter value in microsecond. */
+	val = readl_relaxed(wdt->tmr->regs + TMRSR);
+	timeleft = FIELD_GET(TMRSR_PCV, val);
+
+	/*
+	 * Calculate the time remaining by adding the time for the
+	 * counter value to the time of the counter expirations that
+	 * remain.
+	 */
+	timeleft += (((u64)wdt->base.timeout * USEC_PER_SEC) / 5) * (4 - expiration);
+
+	/*
+	 * Convert the current counter value to seconds,
+	 * rounding up to the nearest second. Cast u64 to
+	 * u32 under the assumption that no overflow happens
+	 * when coverting to seconds.
+	 */
+	timeleft = DIV_ROUND_CLOSEST_ULL(timeleft, USEC_PER_SEC);
+
+	if (WARN_ON_ONCE(timeleft > U32_MAX))
+		return U32_MAX;
+
+	return lower_32_bits(timeleft);
+}
+
 static const struct watchdog_ops tegra186_wdt_ops = {
 	.owner = THIS_MODULE,
 	.start = tegra186_wdt_start,
 	.stop = tegra186_wdt_stop,
 	.ping = tegra186_wdt_ping,
 	.set_timeout = tegra186_wdt_set_timeout,
+	.get_timeleft = tegra186_wdt_get_timeleft,
 };
 
 static struct tegra186_wdt *tegra186_wdt_create(struct tegra186_timer *tegra,
-- 
2.34.1
Re: [PATCH v8 1/3] clocksource/drivers/timer-tegra186: add WDIOC_GETTIMELEFT support
Posted by Guenter Roeck 6 months ago 
Hi,

On Wed, May 07, 2025 at 12:43:09PM +0800, Robert Lin wrote:
> From: Pohsun Su <pohsuns@nvidia.com>
> 
> This change adds support for WDIOC_GETTIMELEFT so userspace
> programs can get the number of seconds before system reset by
> the watchdog timer via ioctl.
> 
> Signed-off-by: Pohsun Su <pohsuns@nvidia.com>
> Signed-off-by: Robert Lin <robelin@nvidia.com>
> ---
>  drivers/clocksource/timer-tegra186.c | 64 +++++++++++++++++++++++++++-
>  1 file changed, 63 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/clocksource/timer-tegra186.c b/drivers/clocksource/timer-tegra186.c
> index ea742889ee06..e3ea6110e6f5 100644
> --- a/drivers/clocksource/timer-tegra186.c
> +++ b/drivers/clocksource/timer-tegra186.c
> @@ -1,8 +1,9 @@
>  // SPDX-License-Identifier: GPL-2.0-only
>  /*
> - * Copyright (c) 2019-2020 NVIDIA Corporation. All rights reserved.
> + * Copyright (c) 2019-2025 NVIDIA Corporation. All rights reserved.
>   */
>  
> +#include <linux/bitfield.h>
>  #include <linux/clocksource.h>
>  #include <linux/module.h>
>  #include <linux/interrupt.h>
> @@ -30,6 +31,7 @@
>  
>  #define TMRSR 0x004
>  #define  TMRSR_INTR_CLR BIT(30)
> +#define  TMRSR_PCV GENMASK(28, 0)
>  
>  #define TMRCSSR 0x008
>  #define  TMRCSSR_SRC_USEC (0 << 0)
> @@ -46,6 +48,9 @@
>  #define  WDTCR_TIMER_SOURCE_MASK 0xf
>  #define  WDTCR_TIMER_SOURCE(x) ((x) & 0xf)
>  
> +#define WDTSR 0x004
> +#define  WDTSR_CURRENT_EXPIRATION_COUNT GENMASK(14, 12)
> +
>  #define WDTCMDR 0x008
>  #define  WDTCMDR_DISABLE_COUNTER BIT(1)
>  #define  WDTCMDR_START_COUNTER BIT(0)
> @@ -235,12 +240,69 @@ static int tegra186_wdt_set_timeout(struct watchdog_device *wdd,
>  	return 0;
>  }
>  
> +static unsigned int tegra186_wdt_get_timeleft(struct watchdog_device *wdd)
> +{
> +	struct tegra186_wdt *wdt = to_tegra186_wdt(wdd);
> +	u32 expiration, val;
> +	u64 timeleft;
> +
> +	if (!watchdog_active(&wdt->base)) {
> +		/* return zero if the watchdog timer is not activated. */
> +		return 0;
> +	}
> +
> +	/*
> +	 * Reset occurs on the fifth expiration of the
> +	 * watchdog timer and so when the watchdog timer is configured,
> +	 * the actual value programmed into the counter is 1/5 of the
> +	 * timeout value. Once the counter reaches 0, expiration count
> +	 * will be increased by 1 and the down counter restarts.
> +	 * Hence to get the time left before system reset we must
> +	 * combine 2 parts:
> +	 * 1. value of the current down counter
> +	 * 2. (number of counter expirations remaining) * (timeout/5)
> +	 */
> +
> +	/* Get the current number of counter expirations. Should be a
> +	 * value between 0 and 4
> +	 */
> +	val = readl_relaxed(wdt->regs + WDTSR);
> +	expiration = FIELD_GET(WDTSR_CURRENT_EXPIRATION_COUNT, val);
> +	if (WARN_ON_ONCE(expiration > 4))
> +		return 0;
> +
> +	/* Get the current counter value in microsecond. */
> +	val = readl_relaxed(wdt->tmr->regs + TMRSR);
> +	timeleft = FIELD_GET(TMRSR_PCV, val);
> +
> +	/*
> +	 * Calculate the time remaining by adding the time for the
> +	 * counter value to the time of the counter expirations that
> +	 * remain.
> +	 */
> +	timeleft += (((u64)wdt->base.timeout * USEC_PER_SEC) / 5) * (4 - expiration);

This results in

xtensa-linux-ld: drivers/clocksource/timer-tegra186.o: in function `tegra186_timer_remove':
timer-tegra186.c:(.text+0x350): undefined reference to `__udivdi3'
xtensa-linux-ld: drivers/clocksource/timer-tegra186.o: in function `tegra186_wdt_get_timeleft':
timer-tegra186.c:(.text+0x52c): undefined reference to `__udivdi3'

when trying to build xtensa:allmodconfig.

Guenter
Re: [PATCH v8 1/3] clocksource/drivers/timer-tegra186: add WDIOC_GETTIMELEFT support
Posted by Thierry Reding 5 months, 4 weeks ago 
On Fri, Jun 13, 2025 at 06:24:40AM -0700, Guenter Roeck wrote:
> Hi,
> 
> On Wed, May 07, 2025 at 12:43:09PM +0800, Robert Lin wrote:
> > From: Pohsun Su <pohsuns@nvidia.com>
> > 
> > This change adds support for WDIOC_GETTIMELEFT so userspace
> > programs can get the number of seconds before system reset by
> > the watchdog timer via ioctl.
> > 
> > Signed-off-by: Pohsun Su <pohsuns@nvidia.com>
> > Signed-off-by: Robert Lin <robelin@nvidia.com>
> > ---
> >  drivers/clocksource/timer-tegra186.c | 64 +++++++++++++++++++++++++++-
> >  1 file changed, 63 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/clocksource/timer-tegra186.c b/drivers/clocksource/timer-tegra186.c
> > index ea742889ee06..e3ea6110e6f5 100644
> > --- a/drivers/clocksource/timer-tegra186.c
> > +++ b/drivers/clocksource/timer-tegra186.c
> > @@ -1,8 +1,9 @@
> >  // SPDX-License-Identifier: GPL-2.0-only
> >  /*
> > - * Copyright (c) 2019-2020 NVIDIA Corporation. All rights reserved.
> > + * Copyright (c) 2019-2025 NVIDIA Corporation. All rights reserved.
> >   */
> >  
> > +#include <linux/bitfield.h>
> >  #include <linux/clocksource.h>
> >  #include <linux/module.h>
> >  #include <linux/interrupt.h>
> > @@ -30,6 +31,7 @@
> >  
> >  #define TMRSR 0x004
> >  #define  TMRSR_INTR_CLR BIT(30)
> > +#define  TMRSR_PCV GENMASK(28, 0)
> >  
> >  #define TMRCSSR 0x008
> >  #define  TMRCSSR_SRC_USEC (0 << 0)
> > @@ -46,6 +48,9 @@
> >  #define  WDTCR_TIMER_SOURCE_MASK 0xf
> >  #define  WDTCR_TIMER_SOURCE(x) ((x) & 0xf)
> >  
> > +#define WDTSR 0x004
> > +#define  WDTSR_CURRENT_EXPIRATION_COUNT GENMASK(14, 12)
> > +
> >  #define WDTCMDR 0x008
> >  #define  WDTCMDR_DISABLE_COUNTER BIT(1)
> >  #define  WDTCMDR_START_COUNTER BIT(0)
> > @@ -235,12 +240,69 @@ static int tegra186_wdt_set_timeout(struct watchdog_device *wdd,
> >  	return 0;
> >  }
> >  
> > +static unsigned int tegra186_wdt_get_timeleft(struct watchdog_device *wdd)
> > +{
> > +	struct tegra186_wdt *wdt = to_tegra186_wdt(wdd);
> > +	u32 expiration, val;
> > +	u64 timeleft;
> > +
> > +	if (!watchdog_active(&wdt->base)) {
> > +		/* return zero if the watchdog timer is not activated. */
> > +		return 0;
> > +	}
> > +
> > +	/*
> > +	 * Reset occurs on the fifth expiration of the
> > +	 * watchdog timer and so when the watchdog timer is configured,
> > +	 * the actual value programmed into the counter is 1/5 of the
> > +	 * timeout value. Once the counter reaches 0, expiration count
> > +	 * will be increased by 1 and the down counter restarts.
> > +	 * Hence to get the time left before system reset we must
> > +	 * combine 2 parts:
> > +	 * 1. value of the current down counter
> > +	 * 2. (number of counter expirations remaining) * (timeout/5)
> > +	 */
> > +
> > +	/* Get the current number of counter expirations. Should be a
> > +	 * value between 0 and 4
> > +	 */
> > +	val = readl_relaxed(wdt->regs + WDTSR);
> > +	expiration = FIELD_GET(WDTSR_CURRENT_EXPIRATION_COUNT, val);
> > +	if (WARN_ON_ONCE(expiration > 4))
> > +		return 0;
> > +
> > +	/* Get the current counter value in microsecond. */
> > +	val = readl_relaxed(wdt->tmr->regs + TMRSR);
> > +	timeleft = FIELD_GET(TMRSR_PCV, val);
> > +
> > +	/*
> > +	 * Calculate the time remaining by adding the time for the
> > +	 * counter value to the time of the counter expirations that
> > +	 * remain.
> > +	 */
> > +	timeleft += (((u64)wdt->base.timeout * USEC_PER_SEC) / 5) * (4 - expiration);
> 
> This results in
> 
> xtensa-linux-ld: drivers/clocksource/timer-tegra186.o: in function `tegra186_timer_remove':
> timer-tegra186.c:(.text+0x350): undefined reference to `__udivdi3'
> xtensa-linux-ld: drivers/clocksource/timer-tegra186.o: in function `tegra186_wdt_get_timeleft':
> timer-tegra186.c:(.text+0x52c): undefined reference to `__udivdi3'

I'm unable to reproduce this. I wonder if maybe I have a different
toolchain that doesn't have this issue? Do you have a link so I can try
to get closer to the setup you have?

Thanks,
Thierry
Re: [PATCH v8 1/3] clocksource/drivers/timer-tegra186: add WDIOC_GETTIMELEFT support
Posted by Guenter Roeck 5 months, 4 weeks ago 
On 6/19/25 03:03, Thierry Reding wrote:
> On Fri, Jun 13, 2025 at 06:24:40AM -0700, Guenter Roeck wrote:
>> Hi,
>>
>> On Wed, May 07, 2025 at 12:43:09PM +0800, Robert Lin wrote:
>>> From: Pohsun Su <pohsuns@nvidia.com>
>>>
>>> This change adds support for WDIOC_GETTIMELEFT so userspace
>>> programs can get the number of seconds before system reset by
>>> the watchdog timer via ioctl.
>>>
>>> Signed-off-by: Pohsun Su <pohsuns@nvidia.com>
>>> Signed-off-by: Robert Lin <robelin@nvidia.com>
>>> ---
>>>   drivers/clocksource/timer-tegra186.c | 64 +++++++++++++++++++++++++++-
>>>   1 file changed, 63 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/clocksource/timer-tegra186.c b/drivers/clocksource/timer-tegra186.c
>>> index ea742889ee06..e3ea6110e6f5 100644
>>> --- a/drivers/clocksource/timer-tegra186.c
>>> +++ b/drivers/clocksource/timer-tegra186.c
>>> @@ -1,8 +1,9 @@
>>>   // SPDX-License-Identifier: GPL-2.0-only
>>>   /*
>>> - * Copyright (c) 2019-2020 NVIDIA Corporation. All rights reserved.
>>> + * Copyright (c) 2019-2025 NVIDIA Corporation. All rights reserved.
>>>    */
>>>   
>>> +#include <linux/bitfield.h>
>>>   #include <linux/clocksource.h>
>>>   #include <linux/module.h>
>>>   #include <linux/interrupt.h>
>>> @@ -30,6 +31,7 @@
>>>   
>>>   #define TMRSR 0x004
>>>   #define  TMRSR_INTR_CLR BIT(30)
>>> +#define  TMRSR_PCV GENMASK(28, 0)
>>>   
>>>   #define TMRCSSR 0x008
>>>   #define  TMRCSSR_SRC_USEC (0 << 0)
>>> @@ -46,6 +48,9 @@
>>>   #define  WDTCR_TIMER_SOURCE_MASK 0xf
>>>   #define  WDTCR_TIMER_SOURCE(x) ((x) & 0xf)
>>>   
>>> +#define WDTSR 0x004
>>> +#define  WDTSR_CURRENT_EXPIRATION_COUNT GENMASK(14, 12)
>>> +
>>>   #define WDTCMDR 0x008
>>>   #define  WDTCMDR_DISABLE_COUNTER BIT(1)
>>>   #define  WDTCMDR_START_COUNTER BIT(0)
>>> @@ -235,12 +240,69 @@ static int tegra186_wdt_set_timeout(struct watchdog_device *wdd,
>>>   	return 0;
>>>   }
>>>   
>>> +static unsigned int tegra186_wdt_get_timeleft(struct watchdog_device *wdd)
>>> +{
>>> +	struct tegra186_wdt *wdt = to_tegra186_wdt(wdd);
>>> +	u32 expiration, val;
>>> +	u64 timeleft;
>>> +
>>> +	if (!watchdog_active(&wdt->base)) {
>>> +		/* return zero if the watchdog timer is not activated. */
>>> +		return 0;
>>> +	}
>>> +
>>> +	/*
>>> +	 * Reset occurs on the fifth expiration of the
>>> +	 * watchdog timer and so when the watchdog timer is configured,
>>> +	 * the actual value programmed into the counter is 1/5 of the
>>> +	 * timeout value. Once the counter reaches 0, expiration count
>>> +	 * will be increased by 1 and the down counter restarts.
>>> +	 * Hence to get the time left before system reset we must
>>> +	 * combine 2 parts:
>>> +	 * 1. value of the current down counter
>>> +	 * 2. (number of counter expirations remaining) * (timeout/5)
>>> +	 */
>>> +
>>> +	/* Get the current number of counter expirations. Should be a
>>> +	 * value between 0 and 4
>>> +	 */
>>> +	val = readl_relaxed(wdt->regs + WDTSR);
>>> +	expiration = FIELD_GET(WDTSR_CURRENT_EXPIRATION_COUNT, val);
>>> +	if (WARN_ON_ONCE(expiration > 4))
>>> +		return 0;
>>> +
>>> +	/* Get the current counter value in microsecond. */
>>> +	val = readl_relaxed(wdt->tmr->regs + TMRSR);
>>> +	timeleft = FIELD_GET(TMRSR_PCV, val);
>>> +
>>> +	/*
>>> +	 * Calculate the time remaining by adding the time for the
>>> +	 * counter value to the time of the counter expirations that
>>> +	 * remain.
>>> +	 */
>>> +	timeleft += (((u64)wdt->base.timeout * USEC_PER_SEC) / 5) * (4 - expiration);
>>
>> This results in
>>
>> xtensa-linux-ld: drivers/clocksource/timer-tegra186.o: in function `tegra186_timer_remove':
>> timer-tegra186.c:(.text+0x350): undefined reference to `__udivdi3'
>> xtensa-linux-ld: drivers/clocksource/timer-tegra186.o: in function `tegra186_wdt_get_timeleft':
>> timer-tegra186.c:(.text+0x52c): undefined reference to `__udivdi3'
> 
> I'm unable to reproduce this. I wonder if maybe I have a different
> toolchain that doesn't have this issue? Do you have a link so I can try
> to get closer to the setup you have?
> 

I found that the problem is only seen with certain versions of gcc,
and only with certain architectures. I noticed it with gcc 13.3 and
13.4 when building xtensa:allmodconfig images. gcc 14.3 does not have
the problem. I did not try with other versions of gcc or clang.

Guenter
[tip: timers/clocksource] clocksource/drivers/timer-tegra186: Add WDIOC_GETTIMELEFT support
Posted by tip-bot2 for Pohsun Su 6 months, 3 weeks ago 
The following commit has been merged into the timers/clocksource branch of tip:

Commit-ID:     28c842c8b0f5d1c2da823b11326e63cdfdbc3def
Gitweb:        https://git.kernel.org/tip/28c842c8b0f5d1c2da823b11326e63cdfdbc3def
Author:        Pohsun Su <pohsuns@nvidia.com>
AuthorDate:    Wed, 07 May 2025 12:43:09 +08:00
Committer:     Daniel Lezcano <daniel.lezcano@linaro.org>
CommitterDate: Fri, 16 May 2025 11:10:32 +02:00

clocksource/drivers/timer-tegra186: Add WDIOC_GETTIMELEFT support

This change adds support for WDIOC_GETTIMELEFT so userspace
programs can get the number of seconds before system reset by
the watchdog timer via ioctl.

Signed-off-by: Pohsun Su <pohsuns@nvidia.com>
Signed-off-by: Robert Lin <robelin@nvidia.com>
Link: https://lore.kernel.org/r/20250507044311.3751033-2-robelin@nvidia.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 drivers/clocksource/timer-tegra186.c | 64 ++++++++++++++++++++++++++-
 1 file changed, 63 insertions(+), 1 deletion(-)

diff --git a/drivers/clocksource/timer-tegra186.c b/drivers/clocksource/timer-tegra186.c
index 5d4cf52..5eb6b7e 100644
--- a/drivers/clocksource/timer-tegra186.c
+++ b/drivers/clocksource/timer-tegra186.c
@@ -1,8 +1,9 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /*
- * Copyright (c) 2019-2020 NVIDIA Corporation. All rights reserved.
+ * Copyright (c) 2019-2025 NVIDIA Corporation. All rights reserved.
  */
 
+#include <linux/bitfield.h>
 #include <linux/clocksource.h>
 #include <linux/module.h>
 #include <linux/interrupt.h>
@@ -29,6 +30,7 @@
 
 #define TMRSR 0x004
 #define  TMRSR_INTR_CLR BIT(30)
+#define  TMRSR_PCV GENMASK(28, 0)
 
 #define TMRCSSR 0x008
 #define  TMRCSSR_SRC_USEC (0 << 0)
@@ -45,6 +47,9 @@
 #define  WDTCR_TIMER_SOURCE_MASK 0xf
 #define  WDTCR_TIMER_SOURCE(x) ((x) & 0xf)
 
+#define WDTSR 0x004
+#define  WDTSR_CURRENT_EXPIRATION_COUNT GENMASK(14, 12)
+
 #define WDTCMDR 0x008
 #define  WDTCMDR_DISABLE_COUNTER BIT(1)
 #define  WDTCMDR_START_COUNTER BIT(0)
@@ -234,12 +239,69 @@ static int tegra186_wdt_set_timeout(struct watchdog_device *wdd,
 	return 0;
 }
 
+static unsigned int tegra186_wdt_get_timeleft(struct watchdog_device *wdd)
+{
+	struct tegra186_wdt *wdt = to_tegra186_wdt(wdd);
+	u32 expiration, val;
+	u64 timeleft;
+
+	if (!watchdog_active(&wdt->base)) {
+		/* return zero if the watchdog timer is not activated. */
+		return 0;
+	}
+
+	/*
+	 * Reset occurs on the fifth expiration of the
+	 * watchdog timer and so when the watchdog timer is configured,
+	 * the actual value programmed into the counter is 1/5 of the
+	 * timeout value. Once the counter reaches 0, expiration count
+	 * will be increased by 1 and the down counter restarts.
+	 * Hence to get the time left before system reset we must
+	 * combine 2 parts:
+	 * 1. value of the current down counter
+	 * 2. (number of counter expirations remaining) * (timeout/5)
+	 */
+
+	/* Get the current number of counter expirations. Should be a
+	 * value between 0 and 4
+	 */
+	val = readl_relaxed(wdt->regs + WDTSR);
+	expiration = FIELD_GET(WDTSR_CURRENT_EXPIRATION_COUNT, val);
+	if (WARN_ON_ONCE(expiration > 4))
+		return 0;
+
+	/* Get the current counter value in microsecond. */
+	val = readl_relaxed(wdt->tmr->regs + TMRSR);
+	timeleft = FIELD_GET(TMRSR_PCV, val);
+
+	/*
+	 * Calculate the time remaining by adding the time for the
+	 * counter value to the time of the counter expirations that
+	 * remain.
+	 */
+	timeleft += (((u64)wdt->base.timeout * USEC_PER_SEC) / 5) * (4 - expiration);
+
+	/*
+	 * Convert the current counter value to seconds,
+	 * rounding up to the nearest second. Cast u64 to
+	 * u32 under the assumption that no overflow happens
+	 * when coverting to seconds.
+	 */
+	timeleft = DIV_ROUND_CLOSEST_ULL(timeleft, USEC_PER_SEC);
+
+	if (WARN_ON_ONCE(timeleft > U32_MAX))
+		return U32_MAX;
+
+	return lower_32_bits(timeleft);
+}
+
 static const struct watchdog_ops tegra186_wdt_ops = {
 	.owner = THIS_MODULE,
 	.start = tegra186_wdt_start,
 	.stop = tegra186_wdt_stop,
 	.ping = tegra186_wdt_ping,
 	.set_timeout = tegra186_wdt_set_timeout,
+	.get_timeleft = tegra186_wdt_get_timeleft,
 };
 
 static struct tegra186_wdt *tegra186_wdt_create(struct tegra186_timer *tegra,

Patchew 2.1-devel-b67e4c2

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