[PATCH v2] watchdog: rti_wdt: Drop RPM count when unused

[PATCH v2] watchdog: rti_wdt: Drop RPM count when unused

[Vignesh Raghavendra]

Do a RPM put if watchdog is not already started during probe and re
enable it in watchdog start.

On K3 SoCs, watchdogs and their corresponding CPUs are under same PD, so
if the reference count of unused watchdogs aren't dropped, it will lead
to CPU hotplug failures as Device Management firmware won't allow to
turn off the PD due to dangling reference count.

Fixes: 2d63908bdbfb ("watchdog: Add K3 RTI watchdog support")
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
---

v2:
* Drop 1/2 (will be posted along with runtime_pm callbacks)
* Use pm_runtime_resume_and_get() instead of pm_runtime_get_sync() which
 takes care of err handling

v1: lore.kernel.org/r/20231110100726.2930218-1-vigneshr@ti.com

 drivers/watchdog/rti_wdt.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c
index 8e1be7ba0103..9215793a1c81 100644
--- a/drivers/watchdog/rti_wdt.c
+++ b/drivers/watchdog/rti_wdt.c
@@ -77,6 +77,11 @@ static int rti_wdt_start(struct watchdog_device *wdd)
 {
 	u32 timer_margin;
 	struct rti_wdt_device *wdt = watchdog_get_drvdata(wdd);
+	int ret;
+
+	ret = pm_runtime_resume_and_get(wdd->parent);
+	if (ret)
+		return ret;
 
 	/* set timeout period */
 	timer_margin = (u64)wdd->timeout * wdt->freq;
@@ -343,6 +348,9 @@ static int rti_wdt_probe(struct platform_device *pdev)
 	if (last_ping)
 		watchdog_set_last_hw_keepalive(wdd, last_ping);
 
+	if (!watchdog_hw_running(wdd))
+		pm_runtime_put_sync(&pdev->dev);
+
 	return 0;
 
 err_iomap:
@@ -357,7 +365,10 @@ static void rti_wdt_remove(struct platform_device *pdev)
 	struct rti_wdt_device *wdt = platform_get_drvdata(pdev);
 
 	watchdog_unregister_device(&wdt->wdd);
-	pm_runtime_put(&pdev->dev);
+
+	if (!pm_runtime_suspended(&pdev->dev))
+		pm_runtime_put(&pdev->dev);
+
 	pm_runtime_disable(&pdev->dev);
 }
 
-- 
2.42.0

Re: [PATCH v2] watchdog: rti_wdt: Drop RPM count when unused

[Manorit Chawdhry]

Hi Vignesh,

On 09:46-20231122, Vignesh Raghavendra wrote:
> Do a RPM put if watchdog is not already started during probe and re
> enable it in watchdog start.
> 
> On K3 SoCs, watchdogs and their corresponding CPUs are under same PD, so
> if the reference count of unused watchdogs aren't dropped, it will lead
> to CPU hotplug failures as Device Management firmware won't allow to
> turn off the PD due to dangling reference count.
> 
> Fixes: 2d63908bdbfb ("watchdog: Add K3 RTI watchdog support")
> Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
> ---
> 
> v2:
> * Drop 1/2 (will be posted along with runtime_pm callbacks)
> * Use pm_runtime_resume_and_get() instead of pm_runtime_get_sync() which
>  takes care of err handling
> 
> v1: lore.kernel.org/r/20231110100726.2930218-1-vigneshr@ti.com
> 
>  drivers/watchdog/rti_wdt.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c
> index 8e1be7ba0103..9215793a1c81 100644
> --- a/drivers/watchdog/rti_wdt.c
> +++ b/drivers/watchdog/rti_wdt.c
> @@ -77,6 +77,11 @@ static int rti_wdt_start(struct watchdog_device *wdd)
>  {
>  	u32 timer_margin;
>  	struct rti_wdt_device *wdt = watchdog_get_drvdata(wdd);
> +	int ret;
> +
> +	ret = pm_runtime_resume_and_get(wdd->parent);
> +	if (ret)
> +		return ret;
>  
>  	/* set timeout period */
>  	timer_margin = (u64)wdd->timeout * wdt->freq;
> @@ -343,6 +348,9 @@ static int rti_wdt_probe(struct platform_device *pdev)
>  	if (last_ping)
>  		watchdog_set_last_hw_keepalive(wdd, last_ping);
>  
> +	if (!watchdog_hw_running(wdd))
> +		pm_runtime_put_sync(&pdev->dev);
> +
>  	return 0;
>  
>  err_iomap:
> @@ -357,7 +365,10 @@ static void rti_wdt_remove(struct platform_device *pdev)
>  	struct rti_wdt_device *wdt = platform_get_drvdata(pdev);
>  
>  	watchdog_unregister_device(&wdt->wdd);
> -	pm_runtime_put(&pdev->dev);
> +
> +	if (!pm_runtime_suspended(&pdev->dev))
> +		pm_runtime_put(&pdev->dev);
> +
>  	pm_runtime_disable(&pdev->dev);
>  }
>  

Tested the following on j721s2 evm.
https://gist.github.com/manorit2001/05a85582fea670d39cc3cfb2df1e5328

Tested-by: Manorit Chawdhry <m-chawdhry@ti.com>

Regards,
Manorit

> -- 
> 2.42.0
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v2] watchdog: rti_wdt: Drop RPM count when unused

[Guenter Roeck]

On 11/21/23 20:16, Vignesh Raghavendra wrote:
> Do a RPM put if watchdog is not already started during probe and re
> enable it in watchdog start.
> 
> On K3 SoCs, watchdogs and their corresponding CPUs are under same PD, so
> if the reference count of unused watchdogs aren't dropped, it will lead
> to CPU hotplug failures as Device Management firmware won't allow to
> turn off the PD due to dangling reference count.
> 
> Fixes: 2d63908bdbfb ("watchdog: Add K3 RTI watchdog support")
> Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>

I always find it amazing that people think everyone would understand the TLAs
(three-letter-acronyms) they use. While those who don't might find it confusing
why a watchdog driver would need or want to drop rotation-per-minute counts,
and what that has to do with police departments, that isn't worth
arguing about

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

Guenter

Re: [PATCH v2] watchdog: rti_wdt: Drop RPM count when unused

[Vignesh Raghavendra]

On 12/12/23 20:57, Guenter Roeck wrote:
> On 11/21/23 20:16, Vignesh Raghavendra wrote:
>> Do a RPM put if watchdog is not already started during probe and re
>> enable it in watchdog start.
>>
>> On K3 SoCs, watchdogs and their corresponding CPUs are under same PD, so
>> if the reference count of unused watchdogs aren't dropped, it will lead
>> to CPU hotplug failures as Device Management firmware won't allow to
>> turn off the PD due to dangling reference count.
>>
>> Fixes: 2d63908bdbfb ("watchdog: Add K3 RTI watchdog support")
>> Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
> 
> I always find it amazing that people think everyone would understand the
> TLAs
> (three-letter-acronyms) they use. While those who don't might find it
> confusing
> why a watchdog driver would need or want to drop rotation-per-minute
> counts,
> and what that has to do with police departments, that isn't worth
> arguing about
> 

Oops, my apologies. I will respin with TLAs expanded

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

Thanks!

> Guenter
> 

-- 
Regards
Vignesh