diff mbox series

[v2] watchdog: rti_wdt: Set min_hw_heartbeat_ms to accommodate 5% safety margin

Message ID 20240404153319.1088644-1-jm@ti.com (mailing list archive)
State New
Headers show
Series [v2] watchdog: rti_wdt: Set min_hw_heartbeat_ms to accommodate 5% safety margin | expand

Commit Message

Judith Mendez April 4, 2024, 3:33 p.m. UTC 
On AM62x, the watchdog is pet before the valid window
is open. Fix min_hw_heartbeat and accommodate a 5% safety
margin with the exception of open window size < 10%,
which shall use <5% due to the smaller open window size.

cc: stable@vger.kernel.org
Fixes: 5527483f8f7c (" watchdog: rti-wdt: attach to running watchdog during probe")
Signed-off-by: Judith Mendez <jm@ti.com>
---
 drivers/watchdog/rti_wdt.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)


base-commit: 860bbe8e618fd62446309e286ab4a83d38201c0a

Comments

Rafael Beims April 5, 2024, 1:11 p.m. UTC | #1 
On 04/04/2024 12:33, Judith Mendez wrote:
> On AM62x, the watchdog is pet before the valid window
> is open. Fix min_hw_heartbeat and accommodate a 5% safety
> margin with the exception of open window size < 10%,
> which shall use <5% due to the smaller open window size.
>
> cc: stable@vger.kernel.org
> Fixes: 5527483f8f7c (" watchdog: rti-wdt: attach to running watchdog during probe")
> Signed-off-by: Judith Mendez <jm@ti.com>
> ---
>   drivers/watchdog/rti_wdt.c | 24 +++++++++++++-----------
>   1 file changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c
> index 8e1be7ba0103..0b16ada659cc 100644
> --- a/drivers/watchdog/rti_wdt.c
> +++ b/drivers/watchdog/rti_wdt.c
> @@ -92,7 +92,7 @@ static int rti_wdt_start(struct watchdog_device *wdd)
>   	 * to be 50% or less than that; we obviouly want to configure the open
>   	 * window as large as possible so we select the 50% option.
>   	 */
> -	wdd->min_hw_heartbeat_ms = 500 * wdd->timeout;
> +	wdd->min_hw_heartbeat_ms = 550 * wdd->timeout;
>   
>   	/* Generate NMI when wdt expires */
>   	writel_relaxed(RTIWWDRX_NMI, wdt->base + RTIWWDRXCTRL);
> @@ -126,31 +126,33 @@ static int rti_wdt_setup_hw_hb(struct watchdog_device *wdd, u32 wsize)
>   	 * be petted during the open window; not too early or not too late.
>   	 * The HW configuration options only allow for the open window size
>   	 * to be 50% or less than that.
> +	 * To avoid any glitches, we accommodate 5% safety margin, with the
> +	 * exception of open window size < 10%.
>   	 */
>   	switch (wsize) {
>   	case RTIWWDSIZE_50P:
> -		/* 50% open window => 50% min heartbeat */
> -		wdd->min_hw_heartbeat_ms = 500 * heartbeat;
> +		/* 50% open window => 55% min heartbeat */
> +		wdd->min_hw_heartbeat_ms = 550 * heartbeat;
>   		break;
>   
>   	case RTIWWDSIZE_25P:
> -		/* 25% open window => 75% min heartbeat */
> -		wdd->min_hw_heartbeat_ms = 750 * heartbeat;
> +		/* 25% open window => 80% min heartbeat */
> +		wdd->min_hw_heartbeat_ms = 800 * heartbeat;
>   		break;
>   
>   	case RTIWWDSIZE_12P5:
> -		/* 12.5% open window => 87.5% min heartbeat */
> -		wdd->min_hw_heartbeat_ms = 875 * heartbeat;
> +		/* 12.5% open window => 92.5% min heartbeat */
> +		wdd->min_hw_heartbeat_ms = 925 * heartbeat;
>   		break;
>   
>   	case RTIWWDSIZE_6P25:
> -		/* 6.5% open window => 93.5% min heartbeat */
> -		wdd->min_hw_heartbeat_ms = 935 * heartbeat;
> +		/* 6.5% open window => 96.5% min heartbeat */
> +		wdd->min_hw_heartbeat_ms = 965 * heartbeat;
>   		break;
>   
>   	case RTIWWDSIZE_3P125:
> -		/* 3.125% open window => 96.9% min heartbeat */
> -		wdd->min_hw_heartbeat_ms = 969 * heartbeat;
> +		/* 3.125% open window => 97.9% min heartbeat */
> +		wdd->min_hw_heartbeat_ms = 979 * heartbeat;
>   		break;
>   
>   	default:
>
> base-commit: 860bbe8e618fd62446309e286ab4a83d38201c0a


Tested-by: Rafael Beims <rafael.beims@toradex.com>


Rafael
Guenter Roeck April 6, 2024, 1:01 p.m. UTC | #2 
On Thu, Apr 04, 2024 at 10:33:19AM -0500, Judith Mendez wrote:
> On AM62x, the watchdog is pet before the valid window
> is open. Fix min_hw_heartbeat and accommodate a 5% safety
> margin with the exception of open window size < 10%,
> which shall use <5% due to the smaller open window size.
> 
> cc: stable@vger.kernel.org
> Fixes: 5527483f8f7c (" watchdog: rti-wdt: attach to running watchdog during probe")
> Signed-off-by: Judith Mendez <jm@ti.com>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> ---
>  drivers/watchdog/rti_wdt.c | 24 +++++++++++++-----------
>  1 file changed, 13 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c
> index 8e1be7ba0103..0b16ada659cc 100644
> --- a/drivers/watchdog/rti_wdt.c
> +++ b/drivers/watchdog/rti_wdt.c
> @@ -92,7 +92,7 @@ static int rti_wdt_start(struct watchdog_device *wdd)
>  	 * to be 50% or less than that; we obviouly want to configure the open
>  	 * window as large as possible so we select the 50% option.
>  	 */
> -	wdd->min_hw_heartbeat_ms = 500 * wdd->timeout;
> +	wdd->min_hw_heartbeat_ms = 550 * wdd->timeout;
>  
>  	/* Generate NMI when wdt expires */
>  	writel_relaxed(RTIWWDRX_NMI, wdt->base + RTIWWDRXCTRL);
> @@ -126,31 +126,33 @@ static int rti_wdt_setup_hw_hb(struct watchdog_device *wdd, u32 wsize)
>  	 * be petted during the open window; not too early or not too late.
>  	 * The HW configuration options only allow for the open window size
>  	 * to be 50% or less than that.
> +	 * To avoid any glitches, we accommodate 5% safety margin, with the
> +	 * exception of open window size < 10%.
>  	 */
>  	switch (wsize) {
>  	case RTIWWDSIZE_50P:
> -		/* 50% open window => 50% min heartbeat */
> -		wdd->min_hw_heartbeat_ms = 500 * heartbeat;
> +		/* 50% open window => 55% min heartbeat */
> +		wdd->min_hw_heartbeat_ms = 550 * heartbeat;
>  		break;
>  
>  	case RTIWWDSIZE_25P:
> -		/* 25% open window => 75% min heartbeat */
> -		wdd->min_hw_heartbeat_ms = 750 * heartbeat;
> +		/* 25% open window => 80% min heartbeat */
> +		wdd->min_hw_heartbeat_ms = 800 * heartbeat;
>  		break;
>  
>  	case RTIWWDSIZE_12P5:
> -		/* 12.5% open window => 87.5% min heartbeat */
> -		wdd->min_hw_heartbeat_ms = 875 * heartbeat;
> +		/* 12.5% open window => 92.5% min heartbeat */
> +		wdd->min_hw_heartbeat_ms = 925 * heartbeat;
>  		break;
>  
>  	case RTIWWDSIZE_6P25:
> -		/* 6.5% open window => 93.5% min heartbeat */
> -		wdd->min_hw_heartbeat_ms = 935 * heartbeat;
> +		/* 6.5% open window => 96.5% min heartbeat */
> +		wdd->min_hw_heartbeat_ms = 965 * heartbeat;
>  		break;
>  
>  	case RTIWWDSIZE_3P125:
> -		/* 3.125% open window => 96.9% min heartbeat */
> -		wdd->min_hw_heartbeat_ms = 969 * heartbeat;
> +		/* 3.125% open window => 97.9% min heartbeat */
> +		wdd->min_hw_heartbeat_ms = 979 * heartbeat;
>  		break;
>  
>  	default:
> 
> base-commit: 860bbe8e618fd62446309e286ab4a83d38201c0a
> -- 
> 2.43.2
> 
>
Judith Mendez April 9, 2024, 7:37 p.m. UTC | #3 
Hi all,

On 4/6/24 8:01 AM, Guenter Roeck wrote:
> On Thu, Apr 04, 2024 at 10:33:19AM -0500, Judith Mendez wrote:
>> On AM62x, the watchdog is pet before the valid window
>> is open. Fix min_hw_heartbeat and accommodate a 5% safety
>> margin with the exception of open window size < 10%,
>> which shall use <5% due to the smaller open window size.

Please do not merge this patch, I will add an additional
patch removing the hack in this driver.

~ Judith
Francesco Dolcini April 9, 2024, 7:52 p.m. UTC | #4 
On Tue, Apr 09, 2024 at 02:37:15PM -0500, Judith Mendez wrote:
> Hi all,
> 
> On 4/6/24 8:01 AM, Guenter Roeck wrote:
> > On Thu, Apr 04, 2024 at 10:33:19AM -0500, Judith Mendez wrote:
> > > On AM62x, the watchdog is pet before the valid window
> > > is open. Fix min_hw_heartbeat and accommodate a 5% safety
> > > margin with the exception of open window size < 10%,
> > > which shall use <5% due to the smaller open window size.
> 
> Please do not merge this patch, I will add an additional
> patch removing the hack in this driver.

Is the patch buggy, or you are just talking about an additional clean-up?
If it is an additional patch and this code is fine, why holding it back?

Thanks,
Francesco
Judith Mendez April 9, 2024, 9:44 p.m. UTC | #5 
Hi Francesco,

On 4/9/24 2:52 PM, Francesco Dolcini wrote:
> On Tue, Apr 09, 2024 at 02:37:15PM -0500, Judith Mendez wrote:
>> Hi all,
>>
>> On 4/6/24 8:01 AM, Guenter Roeck wrote:
>>> On Thu, Apr 04, 2024 at 10:33:19AM -0500, Judith Mendez wrote:
>>>> On AM62x, the watchdog is pet before the valid window
>>>> is open. Fix min_hw_heartbeat and accommodate a 5% safety
>>>> margin with the exception of open window size < 10%,
>>>> which shall use <5% due to the smaller open window size.
>>
>> Please do not merge this patch, I will add an additional
>> patch removing the hack in this driver.
> 
> Is the patch buggy, or you are just talking about an additional clean-up?
> If it is an additional patch and this code is fine, why holding it back?


1. If we leave the hack, the hack shifts the valid window. This
is not desirable behavior. It is better to add a safety margin
that works in all possible scenarios.

2. 5% safety margin works in almost all cases except when the
timeout is < 5s. This due to a requirement of a min of 0.25s for the
safety margin due max possible error. At < 5s timeout, 5% is not
enough.

I am not 100% sure if using < 5s timeout is a real use-case
but I would rather use a safety margin that works for all cases.

~ Judith
diff mbox series

Patch

diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c
index 8e1be7ba0103..0b16ada659cc 100644
--- a/drivers/watchdog/rti_wdt.c
+++ b/drivers/watchdog/rti_wdt.c
@@ -92,7 +92,7 @@  static int rti_wdt_start(struct watchdog_device *wdd)
 	 * to be 50% or less than that; we obviouly want to configure the open
 	 * window as large as possible so we select the 50% option.
 	 */
-	wdd->min_hw_heartbeat_ms = 500 * wdd->timeout;
+	wdd->min_hw_heartbeat_ms = 550 * wdd->timeout;
 
 	/* Generate NMI when wdt expires */
 	writel_relaxed(RTIWWDRX_NMI, wdt->base + RTIWWDRXCTRL);
@@ -126,31 +126,33 @@  static int rti_wdt_setup_hw_hb(struct watchdog_device *wdd, u32 wsize)
 	 * be petted during the open window; not too early or not too late.
 	 * The HW configuration options only allow for the open window size
 	 * to be 50% or less than that.
+	 * To avoid any glitches, we accommodate 5% safety margin, with the
+	 * exception of open window size < 10%.
 	 */
 	switch (wsize) {
 	case RTIWWDSIZE_50P:
-		/* 50% open window => 50% min heartbeat */
-		wdd->min_hw_heartbeat_ms = 500 * heartbeat;
+		/* 50% open window => 55% min heartbeat */
+		wdd->min_hw_heartbeat_ms = 550 * heartbeat;
 		break;
 
 	case RTIWWDSIZE_25P:
-		/* 25% open window => 75% min heartbeat */
-		wdd->min_hw_heartbeat_ms = 750 * heartbeat;
+		/* 25% open window => 80% min heartbeat */
+		wdd->min_hw_heartbeat_ms = 800 * heartbeat;
 		break;
 
 	case RTIWWDSIZE_12P5:
-		/* 12.5% open window => 87.5% min heartbeat */
-		wdd->min_hw_heartbeat_ms = 875 * heartbeat;
+		/* 12.5% open window => 92.5% min heartbeat */
+		wdd->min_hw_heartbeat_ms = 925 * heartbeat;
 		break;
 
 	case RTIWWDSIZE_6P25:
-		/* 6.5% open window => 93.5% min heartbeat */
-		wdd->min_hw_heartbeat_ms = 935 * heartbeat;
+		/* 6.5% open window => 96.5% min heartbeat */
+		wdd->min_hw_heartbeat_ms = 965 * heartbeat;
 		break;
 
 	case RTIWWDSIZE_3P125:
-		/* 3.125% open window => 96.9% min heartbeat */
-		wdd->min_hw_heartbeat_ms = 969 * heartbeat;
+		/* 3.125% open window => 97.9% min heartbeat */
+		wdd->min_hw_heartbeat_ms = 979 * heartbeat;
 		break;
 
 	default: