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[v2,0/2] watchdog: sp805: add reset control support

Message ID 20240220-hisi-wdt-v2-0-63edc4965b4c@outlook.com
Headers show
Series watchdog: sp805: add reset control support | expand

Message

Yang Xiwen via B4 Relay Feb. 19, 2024, 6:14 p.m. UTC
Deassert the reset if it's available.

Signed-off-by: Yang Xiwen <forbidden405@outlook.com>
---
Changes in v2:
- commit log: dt-binding->dt-bindings (Krzysztof Kozlowski)
- binding: remove "|", join two lines. (Krzysztof Kozlowski)
- Link to v1: https://lore.kernel.org/r/20240217-hisi-wdt-v1-0-cdb9ddcab968@outlook.com

---
Yang Xiwen (2):
      watchdog: sp805_wdt: deassert the reset if available
      dt-bindings: watchdog: arm,sp805: document the reset signal

 Documentation/devicetree/bindings/watchdog/arm,sp805.yaml | 5 +++++
 drivers/watchdog/sp805_wdt.c                              | 9 +++++++++
 2 files changed, 14 insertions(+)
---
base-commit: 8d3dea210042f54b952b481838c1e7dfc4ec751d
change-id: 20240217-hisi-wdt-3b52971a6591

Best regards,

Comments

Christophe JAILLET Feb. 19, 2024, 6:22 p.m. UTC | #1
Le 19/02/2024 à 19:14, Yang Xiwen via B4 Relay a écrit :
> From: Yang Xiwen <forbidden405-1ViLX0X+lBJBDgjK7y7TUQ@public.gmane.org>
> 
> According to the datasheet, the core has an WDOGRESn input signal that
> needs to be deasserted before being operational. Implement it in the
> driver.
> 
> Signed-off-by: Yang Xiwen <forbidden405-1ViLX0X+lBJBDgjK7y7TUQ@public.gmane.org>
> ---
>   drivers/watchdog/sp805_wdt.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/watchdog/sp805_wdt.c b/drivers/watchdog/sp805_wdt.c
> index 2756ed54ca3d..b4bcfdeb39e6 100644
> --- a/drivers/watchdog/sp805_wdt.c
> +++ b/drivers/watchdog/sp805_wdt.c
> @@ -25,6 +25,7 @@
>   #include <linux/moduleparam.h>
>   #include <linux/pm.h>
>   #include <linux/property.h>
> +#include <linux/reset.h>
>   #include <linux/slab.h>
>   #include <linux/spinlock.h>
>   #include <linux/types.h>
> @@ -59,6 +60,7 @@
>    * @lock: spin lock protecting dev structure and io access
>    * @base: base address of wdt
>    * @clk: (optional) clock structure of wdt
> + * @rst: (optional) reset control signal of wdt
>    * @rate: (optional) clock rate when provided via properties
>    * @adev: amba device structure of wdt
>    * @status: current status of wdt
> @@ -69,6 +71,7 @@ struct sp805_wdt {
>   	spinlock_t			lock;
>   	void __iomem			*base;
>   	struct clk			*clk;
> +	struct reset_control		*rst;
>   	u64				rate;
>   	struct amba_device		*adev;
>   	unsigned int			load_val;
> @@ -264,6 +267,12 @@ sp805_wdt_probe(struct amba_device *adev, const struct amba_id *id)
>   		return -ENODEV;
>   	}
>   
> +	wdt->rst = devm_reset_control_get_optional(&adev->dev, NULL);
> +	if (IS_ERR(wdt->rst))
> +		return dev_err_probe(&adev->dev, PTR_ERR(wdt->rst), "Can not get reset\n");
> +
> +	reset_control_deassert(wdt->rst);
> +

Hi,

Is a corresponding reset_control_assert() needed in the remove function?

CJ

>   	wdt->adev = adev;
>   	wdt->wdd.info = &wdt_info;
>   	wdt->wdd.ops = &wdt_ops;
>
Yang Xiwen Feb. 19, 2024, 7 p.m. UTC | #2
On 2/20/2024 2:22 AM, Christophe JAILLET wrote:
> Le 19/02/2024 à 19:14, Yang Xiwen via B4 Relay a écrit :
>> From: Yang Xiwen <forbidden405-1ViLX0X+lBJBDgjK7y7TUQ@public.gmane.org>
>>
>> According to the datasheet, the core has an WDOGRESn input signal that
>> needs to be deasserted before being operational. Implement it in the
>> driver.
>>
>> Signed-off-by: Yang Xiwen 
>> <forbidden405-1ViLX0X+lBJBDgjK7y7TUQ@public.gmane.org>
>> ---
>>   drivers/watchdog/sp805_wdt.c | 9 +++++++++
>>   1 file changed, 9 insertions(+)
>>
>> diff --git a/drivers/watchdog/sp805_wdt.c b/drivers/watchdog/sp805_wdt.c
>> index 2756ed54ca3d..b4bcfdeb39e6 100644
>> --- a/drivers/watchdog/sp805_wdt.c
>> +++ b/drivers/watchdog/sp805_wdt.c
>> @@ -25,6 +25,7 @@
>>   #include <linux/moduleparam.h>
>>   #include <linux/pm.h>
>>   #include <linux/property.h>
>> +#include <linux/reset.h>
>>   #include <linux/slab.h>
>>   #include <linux/spinlock.h>
>>   #include <linux/types.h>
>> @@ -59,6 +60,7 @@
>>    * @lock: spin lock protecting dev structure and io access
>>    * @base: base address of wdt
>>    * @clk: (optional) clock structure of wdt
>> + * @rst: (optional) reset control signal of wdt
>>    * @rate: (optional) clock rate when provided via properties
>>    * @adev: amba device structure of wdt
>>    * @status: current status of wdt
>> @@ -69,6 +71,7 @@ struct sp805_wdt {
>>       spinlock_t            lock;
>>       void __iomem            *base;
>>       struct clk            *clk;
>> +    struct reset_control        *rst;
>>       u64                rate;
>>       struct amba_device        *adev;
>>       unsigned int            load_val;
>> @@ -264,6 +267,12 @@ sp805_wdt_probe(struct amba_device *adev, const 
>> struct amba_id *id)
>>           return -ENODEV;
>>       }
>>   +    wdt->rst = devm_reset_control_get_optional(&adev->dev, NULL);
>> +    if (IS_ERR(wdt->rst))
>> +        return dev_err_probe(&adev->dev, PTR_ERR(wdt->rst), "Can not 
>> get reset\n");
>> +
>> +    reset_control_deassert(wdt->rst);
>> +
>
> Hi,
>
> Is a corresponding reset_control_assert() needed in the remove function?

I don't think it makes much sense. Many drivers in kernel does not 
reassert the resets in their driver's remove callback too.

Maybe it can save some power. But since it's already disabled in control 
register. Can't say it's too much.

>
> CJ
>
>>       wdt->adev = adev;
>>       wdt->wdd.info = &wdt_info;
>>       wdt->wdd.ops = &wdt_ops;
>>
>
Philipp Zabel Feb. 21, 2024, 11:48 a.m. UTC | #3
On Di, 2024-02-20 at 02:14 +0800, Yang Xiwen via B4 Relay wrote:
> From: Yang Xiwen <forbidden405@outlook.com>
> 
> According to the datasheet, the core has an WDOGRESn input signal that
> needs to be deasserted before being operational. Implement it in the
> driver.
> 
> Signed-off-by: Yang Xiwen <forbidden405@outlook.com>
> ---
>  drivers/watchdog/sp805_wdt.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/watchdog/sp805_wdt.c b/drivers/watchdog/sp805_wdt.c
> index 2756ed54ca3d..b4bcfdeb39e6 100644
> --- a/drivers/watchdog/sp805_wdt.c
> +++ b/drivers/watchdog/sp805_wdt.c
> @@ -25,6 +25,7 @@
>  #include <linux/moduleparam.h>
>  #include <linux/pm.h>
>  #include <linux/property.h>
> +#include <linux/reset.h>
>  #include <linux/slab.h>
>  #include <linux/spinlock.h>
>  #include <linux/types.h>
> @@ -59,6 +60,7 @@
>   * @lock: spin lock protecting dev structure and io access
>   * @base: base address of wdt
>   * @clk: (optional) clock structure of wdt
> + * @rst: (optional) reset control signal of wdt
>   * @rate: (optional) clock rate when provided via properties
>   * @adev: amba device structure of wdt
>   * @status: current status of wdt
> @@ -69,6 +71,7 @@ struct sp805_wdt {
>  	spinlock_t			lock;
>  	void __iomem			*base;
>  	struct clk			*clk;
> +	struct reset_control		*rst;

This can be a local variable in sp805_wdt_probe().

>  	u64				rate;
>  	struct amba_device		*adev;
>  	unsigned int			load_val;
> @@ -264,6 +267,12 @@ sp805_wdt_probe(struct amba_device *adev, const struct amba_id *id)
>  		return -ENODEV;
>  	}
>  
> +	wdt->rst = devm_reset_control_get_optional(&adev->dev, NULL);

Please use devm_reset_control_get_optional_exclusive() directly.

> +	if (IS_ERR(wdt->rst))
> +		return dev_err_probe(&adev->dev, PTR_ERR(wdt->rst), "Can not get reset\n");
> +
> +	reset_control_deassert(wdt->rst);
> +
>  	wdt->adev = adev;
>  	wdt->wdd.info = &wdt_info;
>  	wdt->wdd.ops = &wdt_ops;

regards
Philipp
Philipp Zabel Feb. 21, 2024, noon UTC | #4
On Di, 2024-02-20 at 03:00 +0800, Yang Xiwen wrote:
> On 2/20/2024 2:22 AM, Christophe JAILLET wrote:
> > Le 19/02/2024 à 19:14, Yang Xiwen via B4 Relay a écrit :
> > > From: Yang Xiwen <forbidden405-1ViLX0X+lBJBDgjK7y7TUQ@public.gmane.org>
> > > 
> > > According to the datasheet, the core has an WDOGRESn input signal that
> > > needs to be deasserted before being operational. Implement it in the
> > > driver.
> > > 
> > > Signed-off-by: Yang Xiwen 
> > > <forbidden405-1ViLX0X+lBJBDgjK7y7TUQ@public.gmane.org>
> > > ---
> > >   drivers/watchdog/sp805_wdt.c | 9 +++++++++
> > >   1 file changed, 9 insertions(+)
> > > 
> > > diff --git a/drivers/watchdog/sp805_wdt.c b/drivers/watchdog/sp805_wdt.c
> > > index 2756ed54ca3d..b4bcfdeb39e6 100644
> > > --- a/drivers/watchdog/sp805_wdt.c
> > > +++ b/drivers/watchdog/sp805_wdt.c
> > > @@ -25,6 +25,7 @@
> > >   #include <linux/moduleparam.h>
> > >   #include <linux/pm.h>
> > >   #include <linux/property.h>
> > > +#include <linux/reset.h>
> > >   #include <linux/slab.h>
> > >   #include <linux/spinlock.h>
> > >   #include <linux/types.h>
> > > @@ -59,6 +60,7 @@
> > >    * @lock: spin lock protecting dev structure and io access
> > >    * @base: base address of wdt
> > >    * @clk: (optional) clock structure of wdt
> > > + * @rst: (optional) reset control signal of wdt
> > >    * @rate: (optional) clock rate when provided via properties
> > >    * @adev: amba device structure of wdt
> > >    * @status: current status of wdt
> > > @@ -69,6 +71,7 @@ struct sp805_wdt {
> > >       spinlock_t            lock;
> > >       void __iomem            *base;
> > >       struct clk            *clk;
> > > +    struct reset_control        *rst;
> > >       u64                rate;
> > >       struct amba_device        *adev;
> > >       unsigned int            load_val;
> > > @@ -264,6 +267,12 @@ sp805_wdt_probe(struct amba_device *adev, const 
> > > struct amba_id *id)
> > >           return -ENODEV;
> > >       }
> > >   +    wdt->rst = devm_reset_control_get_optional(&adev->dev, NULL);
> > > +    if (IS_ERR(wdt->rst))
> > > +        return dev_err_probe(&adev->dev, PTR_ERR(wdt->rst), "Can not 
> > > get reset\n");
> > > +
> > > +    reset_control_deassert(wdt->rst);
> > > +
> > 
> > Hi,
> > 
> > Is a corresponding reset_control_assert() needed in the remove function?
> 
> I don't think it makes much sense. Many drivers in kernel does not 
> reassert the resets in their driver's remove callback too.

In general, balancing deassert/assert is only required for shared reset
controls.

For exclusive reset controls, it depends on whether the driver has any
expectations that the reset was asserted at some point before deassert
is called, possibly to reset registers or some internal state.
E.g., if this driver is unbound and then bound again, the deassert
during second probe is a no-op.

regards
Philipp