[RFC PATCH] watchdog: sp805: Add clock-frequency property

[RFC PATCH] watchdog: sp805: Add clock-frequency property

[Srinath Mannam]

When using ACPI node, binding clock devices are
not available as device tree, So clock-frequency
property given in _DSD object of ACPI device is
used to calculate Watchdog rate.

Signed-off-by: Srinath Mannam <srinath.mannam@broadcom.com>
---
 drivers/watchdog/sp805_wdt.c | 29 ++++++++++++++++++++++++-----
 1 file changed, 24 insertions(+), 5 deletions(-)

diff --git a/drivers/watchdog/sp805_wdt.c b/drivers/watchdog/sp805_wdt.c
index 9849db0..d830dbc 100644
--- a/drivers/watchdog/sp805_wdt.c
+++ b/drivers/watchdog/sp805_wdt.c
@@ -22,6 +22,7 @@
 #include <linux/math64.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
+#include <linux/of.h>
 #include <linux/pm.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
@@ -65,6 +66,7 @@ struct sp805_wdt {
 	spinlock_t			lock;
 	void __iomem			*base;
 	struct clk			*clk;
+	u64				rate;
 	struct amba_device		*adev;
 	unsigned int			load_val;
 };
@@ -80,7 +82,10 @@ static int wdt_setload(struct watchdog_device *wdd, unsigned int timeout)
 	struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
 	u64 load, rate;
 
-	rate = clk_get_rate(wdt->clk);
+	if (wdt->rate)
+		rate = wdt->rate;
+	else
+		rate = clk_get_rate(wdt->clk);
 
 	/*
 	 * sp805 runs counter with given value twice, after the end of first
@@ -108,7 +113,10 @@ static unsigned int wdt_timeleft(struct watchdog_device *wdd)
 	struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
 	u64 load, rate;
 
-	rate = clk_get_rate(wdt->clk);
+	if (wdt->rate)
+		rate = wdt->rate;
+	else
+		rate = clk_get_rate(wdt->clk);
 
 	spin_lock(&wdt->lock);
 	load = readl_relaxed(wdt->base + WDTVALUE);
@@ -230,11 +238,22 @@ sp805_wdt_probe(struct amba_device *adev, const struct amba_id *id)
 
 	wdt->clk = devm_clk_get(&adev->dev, NULL);
 	if (IS_ERR(wdt->clk)) {
-		dev_warn(&adev->dev, "Clock not found\n");
-		ret = PTR_ERR(wdt->clk);
-		goto err;
+		dev_warn(&adev->dev, "Clock device not found\n");
+		wdt->clk = NULL;
+		/*
+		 * When Driver probe with ACPI device, clock devices
+		 * are not available, so watchdog rate get from
+		 * clock-frequency property given in _DSD object.
+		 */
+		device_property_read_u64(&adev->dev, "clock-frequency",
+					 &wdt->rate);
+		if (!wdt->rate) {
+			ret = -ENODEV;
+			goto err;
+		}
 	}
 
+
 	wdt->adev = adev;
 	wdt->wdd.info = &wdt_info;
 	wdt->wdd.ops = &wdt_ops;
-- 
2.7.4

Re: [RFC PATCH] watchdog: sp805: Add clock-frequency property

[Guenter Roeck]

On 07/04/2018 08:22 PM, Srinath Mannam wrote:
> When using ACPI node, binding clock devices are
> not available as device tree, So clock-frequency
> property given in _DSD object of ACPI device is
> used to calculate Watchdog rate.
> 
> Signed-off-by: Srinath Mannam <srinath.mannam@broadcom.com>
> ---
>   drivers/watchdog/sp805_wdt.c | 29 ++++++++++++++++++++++++-----
>   1 file changed, 24 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/watchdog/sp805_wdt.c b/drivers/watchdog/sp805_wdt.c
> index 9849db0..d830dbc 100644
> --- a/drivers/watchdog/sp805_wdt.c
> +++ b/drivers/watchdog/sp805_wdt.c
> @@ -22,6 +22,7 @@
>   #include <linux/math64.h>
>   #include <linux/module.h>
>   #include <linux/moduleparam.h>
> +#include <linux/of.h>
>   #include <linux/pm.h>
>   #include <linux/slab.h>
>   #include <linux/spinlock.h>
> @@ -65,6 +66,7 @@ struct sp805_wdt {
>   	spinlock_t			lock;
>   	void __iomem			*base;
>   	struct clk			*clk;
> +	u64				rate;
>   	struct amba_device		*adev;
>   	unsigned int			load_val;
>   };
> @@ -80,7 +82,10 @@ static int wdt_setload(struct watchdog_device *wdd, unsigned int timeout)
>   	struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
>   	u64 load, rate;
>   
> -	rate = clk_get_rate(wdt->clk);
> +	if (wdt->rate)
> +		rate = wdt->rate;
> +	else
> +		rate = clk_get_rate(wdt->clk);

No. Get the rate once during probe and store it in wdt->rate.

>   
>   	/*
>   	 * sp805 runs counter with given value twice, after the end of first
> @@ -108,7 +113,10 @@ static unsigned int wdt_timeleft(struct watchdog_device *wdd)
>   	struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
>   	u64 load, rate;
>   
> -	rate = clk_get_rate(wdt->clk);
> +	if (wdt->rate)
> +		rate = wdt->rate;
> +	else
> +		rate = clk_get_rate(wdt->clk);

Same here.

>   
>   	spin_lock(&wdt->lock);
>   	load = readl_relaxed(wdt->base + WDTVALUE);
> @@ -230,11 +238,22 @@ sp805_wdt_probe(struct amba_device *adev, const struct amba_id *id)
>   
>   	wdt->clk = devm_clk_get(&adev->dev, NULL);
>   	if (IS_ERR(wdt->clk)) {
> -		dev_warn(&adev->dev, "Clock not found\n");
> -		ret = PTR_ERR(wdt->clk);
> -		goto err;
> +		dev_warn(&adev->dev, "Clock device not found\n");

"Clock _device_" ? Why this change ? And why retain that warning unconditionally ?

> +		wdt->clk = NULL;
> +		/*
> +		 * When Driver probe with ACPI device, clock devices
> +		 * are not available, so watchdog rate get from
> +		 * clock-frequency property given in _DSD object.
> +		 */
> +		device_property_read_u64(&adev->dev, "clock-frequency",
> +					 &wdt->rate);
> +		if (!wdt->rate) {
> +			ret = -ENODEV;

This unconditionally overrides the original error.

> +			goto err;
> +		}
>   	}
>   
> +

No whitespace changes, please.

Does that mean that ACPI doesn't support the clock subsystem and that each driver
supporting ACPI must do this ? That would be messy. Also, the above does not check
if the device was probed through ACPI. It just tries to find an undocumented
"clock-frequency" property which is quite different and would apply to
(probably mis-configured) devicetree files as well.

Either case, I would rather have this addressed through the clock subsystem.
Otherwise, someone with subject knowledge will have to confirm that this is the
appropriate solution. If so, the new property will have to be documented as an
alternative to clock specifiers and accepted by devicetree maintainers.

Guenter

>   	wdt->adev = adev;
>   	wdt->wdd.info = &wdt_info;
>   	wdt->wdd.ops = &wdt_ops;
> 

Re: [RFC PATCH] watchdog: sp805: Add clock-frequency property

[Srinath Mannam]

Hi Guenter,

Thank you very much for your feedback. Please find my comments.

On Thu, Jul 5, 2018 at 8:58 PM, Guenter Roeck <linux@roeck-us.net> wrote:
> On 07/04/2018 08:22 PM, Srinath Mannam wrote:
>>
>> When using ACPI node, binding clock devices are
>> not available as device tree, So clock-frequency
>> property given in _DSD object of ACPI device is
>> used to calculate Watchdog rate.
>>
>> Signed-off-by: Srinath Mannam <srinath.mannam@broadcom.com>
>> ---
>>   drivers/watchdog/sp805_wdt.c | 29 ++++++++++++++++++++++++-----
>>   1 file changed, 24 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/watchdog/sp805_wdt.c b/drivers/watchdog/sp805_wdt.c
>> index 9849db0..d830dbc 100644
>> --- a/drivers/watchdog/sp805_wdt.c
>> +++ b/drivers/watchdog/sp805_wdt.c
>> @@ -22,6 +22,7 @@
>>   #include <linux/math64.h>
>>   #include <linux/module.h>
>>   #include <linux/moduleparam.h>
>> +#include <linux/of.h>
>>   #include <linux/pm.h>
>>   #include <linux/slab.h>
>>   #include <linux/spinlock.h>
>> @@ -65,6 +66,7 @@ struct sp805_wdt {
>>         spinlock_t                      lock;
>>         void __iomem                    *base;
>>         struct clk                      *clk;
>> +       u64                             rate;
>>         struct amba_device              *adev;
>>         unsigned int                    load_val;
>>   };
>> @@ -80,7 +82,10 @@ static int wdt_setload(struct watchdog_device *wdd,
>> unsigned int timeout)
>>         struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
>>         u64 load, rate;
>>   -     rate = clk_get_rate(wdt->clk);
>> +       if (wdt->rate)
>> +               rate = wdt->rate;
>> +       else
>> +               rate = clk_get_rate(wdt->clk);
>
>
> No. Get the rate once during probe and store it in wdt->rate.
clk_get_rate function was called multiple places in the driver.
so that we thought, there may be cases where clock rate can change at run-time.
That is the reason, I keep clk_get_rate function.
>
>>         /*
>>          * sp805 runs counter with given value twice, after the end of
>> first
>> @@ -108,7 +113,10 @@ static unsigned int wdt_timeleft(struct
>> watchdog_device *wdd)
>>         struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
>>         u64 load, rate;
>>   -     rate = clk_get_rate(wdt->clk);
>> +       if (wdt->rate)
>> +               rate = wdt->rate;
>> +       else
>> +               rate = clk_get_rate(wdt->clk);
>
>
> Same here.
>
>>         spin_lock(&wdt->lock);
>>         load = readl_relaxed(wdt->base + WDTVALUE);
>> @@ -230,11 +238,22 @@ sp805_wdt_probe(struct amba_device *adev, const
>> struct amba_id *id)
>>         wdt->clk = devm_clk_get(&adev->dev, NULL);
>>         if (IS_ERR(wdt->clk)) {
>> -               dev_warn(&adev->dev, "Clock not found\n");
>> -               ret = PTR_ERR(wdt->clk);
>> -               goto err;
>> +               dev_warn(&adev->dev, "Clock device not found\n");
>
>
> "Clock _device_" ? Why this change ? And why retain that warning
> unconditionally ?
I mean, peripheral may have clock input but clock device node is not
available to this driver.
So I keep the warning.
I thought to handle this better, divide this part of code into two
parts based on device tree and ACPI.
But this driver implementation is independent of device tree and ACPI calls.
To get device-tree properties watch-dog framework APIs are called ex: timeout.
Can I add ACPI and device tree node availability check to get clock
device and clock-frequency properties. Please advice.
>
>> +               wdt->clk = NULL;
>> +               /*
>> +                * When Driver probe with ACPI device, clock devices
>> +                * are not available, so watchdog rate get from
>> +                * clock-frequency property given in _DSD object.
>> +                */
>> +               device_property_read_u64(&adev->dev, "clock-frequency",
>> +                                        &wdt->rate);
>> +               if (!wdt->rate) {
>> +                       ret = -ENODEV;
>
>
> This unconditionally overrides the original error.
I accept, I will change.
>
>> +                       goto err;
>> +               }
>>         }
>>   +
>
>
> No whitespace changes, please.
I will remove.
>
> Does that mean that ACPI doesn't support the clock subsystem and that each
> driver
> supporting ACPI must do this ? That would be messy. Also, the above does not
> check
> if the device was probed through ACPI. It just tries to find an undocumented
> "clock-frequency" property which is quite different and would apply to
> (probably mis-configured) devicetree files as well.
>
> Either case, I would rather have this addressed through the clock subsystem.
> Otherwise, someone with subject knowledge will have to confirm that this is
> the
> appropriate solution. If so, the new property will have to be documented as
> an
> alternative to clock specifiers and accepted by devicetree maintainers.
>
I checked with ACPI maintainers, ACPI does not support common-clock
framework and also no plan.
AMBA framework also request for "apb_pclk" clock node to enable pclk.
But ACPI does not do the same.
So in device-tree use case, both apb_pclk and wdt clock nodes are
required properties, so passing
clock-frequency alone can not be alternative.
Because ACPI does not support clk node method, I came up with
alternate fixed-clock property clock-frequency.
clock-frequency is only specific to ACPI case, so we can't add in
binding document.
I will add device tree and ACPI specific check to read clock nodes and
clock-frequency properties separately.

If you are fine with this I will send the next patch with modifications.

> Guenter
>
>>         wdt->adev = adev;
>>         wdt->wdd.info = &wdt_info;
>>         wdt->wdd.ops = &wdt_ops;
>>
>
Thank you,

Regards,
Srinath.

Re: [RFC PATCH] watchdog: sp805: Add clock-frequency property

[Guenter Roeck]

On 07/06/2018 01:18 AM, Srinath Mannam wrote:
> Hi Guenter,
> 
> Thank you very much for your feedback. Please find my comments.
> 
> On Thu, Jul 5, 2018 at 8:58 PM, Guenter Roeck <linux@roeck-us.net> wrote:
>> On 07/04/2018 08:22 PM, Srinath Mannam wrote:
>>>
>>> When using ACPI node, binding clock devices are
>>> not available as device tree, So clock-frequency
>>> property given in _DSD object of ACPI device is
>>> used to calculate Watchdog rate.
>>>
>>> Signed-off-by: Srinath Mannam <srinath.mannam@broadcom.com>
>>> ---
>>>    drivers/watchdog/sp805_wdt.c | 29 ++++++++++++++++++++++++-----
>>>    1 file changed, 24 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/watchdog/sp805_wdt.c b/drivers/watchdog/sp805_wdt.c
>>> index 9849db0..d830dbc 100644
>>> --- a/drivers/watchdog/sp805_wdt.c
>>> +++ b/drivers/watchdog/sp805_wdt.c
>>> @@ -22,6 +22,7 @@
>>>    #include <linux/math64.h>
>>>    #include <linux/module.h>
>>>    #include <linux/moduleparam.h>
>>> +#include <linux/of.h>
>>>    #include <linux/pm.h>
>>>    #include <linux/slab.h>
>>>    #include <linux/spinlock.h>
>>> @@ -65,6 +66,7 @@ struct sp805_wdt {
>>>          spinlock_t                      lock;
>>>          void __iomem                    *base;
>>>          struct clk                      *clk;
>>> +       u64                             rate;
>>>          struct amba_device              *adev;
>>>          unsigned int                    load_val;
>>>    };
>>> @@ -80,7 +82,10 @@ static int wdt_setload(struct watchdog_device *wdd,
>>> unsigned int timeout)
>>>          struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
>>>          u64 load, rate;
>>>    -     rate = clk_get_rate(wdt->clk);
>>> +       if (wdt->rate)
>>> +               rate = wdt->rate;
>>> +       else
>>> +               rate = clk_get_rate(wdt->clk);
>>
>>
>> No. Get the rate once during probe and store it in wdt->rate.
> clk_get_rate function was called multiple places in the driver.
> so that we thought, there may be cases where clock rate can change at run-time.
> That is the reason, I keep clk_get_rate function.

This is not an argument. A changing clock rate without notifying the driver
would be fatal for a watchdog driver, since it would affect the timeout and
- if the clock rate is increased - result in arbitrary reboots. If that can
happen with the clock used by this watchdog, some notification would have to
be implemented to let the driver know.

>>
>>>          /*
>>>           * sp805 runs counter with given value twice, after the end of
>>> first
>>> @@ -108,7 +113,10 @@ static unsigned int wdt_timeleft(struct
>>> watchdog_device *wdd)
>>>          struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
>>>          u64 load, rate;
>>>    -     rate = clk_get_rate(wdt->clk);
>>> +       if (wdt->rate)
>>> +               rate = wdt->rate;
>>> +       else
>>> +               rate = clk_get_rate(wdt->clk);
>>
>>
>> Same here.
>>
>>>          spin_lock(&wdt->lock);
>>>          load = readl_relaxed(wdt->base + WDTVALUE);
>>> @@ -230,11 +238,22 @@ sp805_wdt_probe(struct amba_device *adev, const
>>> struct amba_id *id)
>>>          wdt->clk = devm_clk_get(&adev->dev, NULL);
>>>          if (IS_ERR(wdt->clk)) {
>>> -               dev_warn(&adev->dev, "Clock not found\n");
>>> -               ret = PTR_ERR(wdt->clk);
>>> -               goto err;
>>> +               dev_warn(&adev->dev, "Clock device not found\n");
>>
>>
>> "Clock _device_" ? Why this change ? And why retain that warning
>> unconditionally ?
> I mean, peripheral may have clock input but clock device node is not
> available to this driver.
> So I keep the warning.

There is now a warning even though everything is fine, if the clock rate
is provided with the "clock-frequency" property instead of the documented
properties. That is unacceptable. I don't want to get flooded with messages
from people asking what this message is about.

> I thought to handle this better, divide this part of code into two
> parts based on device tree and ACPI.
> But this driver implementation is independent of device tree and ACPI calls.
> To get device-tree properties watch-dog framework APIs are called ex: timeout.
> Can I add ACPI and device tree node availability check to get clock
> device and clock-frequency properties. Please advice.

Sorry, I fail to parse what you are trying to say.

Lets summarize: You are introducing a new means for this driver to obtain
the clock rate used by the watchdog. This is quite independent of the
instantiation method, since it works for both ACPI and non-ACPI systems.
This change needs to be documented and approved by devicetree maintainers.
Its implementation must then accept all valid methods to obtain the clock
rate without warning or error message.

Thanks,
Guenter

>>
>>> +               wdt->clk = NULL;
>>> +               /*
>>> +                * When Driver probe with ACPI device, clock devices
>>> +                * are not available, so watchdog rate get from
>>> +                * clock-frequency property given in _DSD object.
>>> +                */
>>> +               device_property_read_u64(&adev->dev, "clock-frequency",
>>> +                                        &wdt->rate);
>>> +               if (!wdt->rate) {
>>> +                       ret = -ENODEV;
>>
>>
>> This unconditionally overrides the original error.
> I accept, I will change.
>>
>>> +                       goto err;
>>> +               }
>>>          }
>>>    +
>>
>>
>> No whitespace changes, please.
> I will remove.
>>
>> Does that mean that ACPI doesn't support the clock subsystem and that each
>> driver
>> supporting ACPI must do this ? That would be messy. Also, the above does not
>> check
>> if the device was probed through ACPI. It just tries to find an undocumented
>> "clock-frequency" property which is quite different and would apply to
>> (probably mis-configured) devicetree files as well.
>>
>> Either case, I would rather have this addressed through the clock subsystem.
>> Otherwise, someone with subject knowledge will have to confirm that this is
>> the
>> appropriate solution. If so, the new property will have to be documented as
>> an
>> alternative to clock specifiers and accepted by devicetree maintainers.
>>
> I checked with ACPI maintainers, ACPI does not support common-clock
> framework and also no plan.
> AMBA framework also request for "apb_pclk" clock node to enable pclk.
> But ACPI does not do the same.
> So in device-tree use case, both apb_pclk and wdt clock nodes are
> required properties, so passing
> clock-frequency alone can not be alternative.
> Because ACPI does not support clk node method, I came up with
> alternate fixed-clock property clock-frequency.
> clock-frequency is only specific to ACPI case, so we can't add in
> binding document.
> I will add device tree and ACPI specific check to read clock nodes and
> clock-frequency properties separately.
> 
> If you are fine with this I will send the next patch with modifications.
> 
>> Guenter
>>
>>>          wdt->adev = adev;
>>>          wdt->wdd.info = &wdt_info;
>>>          wdt->wdd.ops = &wdt_ops;
>>>
>>
> Thank you,
> 
> Regards,
> Srinath.
> --
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> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

Re: [RFC PATCH] watchdog: sp805: Add clock-frequency property

[Srinath Mannam]

Hi Guenter,

Thank you for the clarification.. Please find my comments.

On Sun, Jul 8, 2018 at 11:36 PM, Guenter Roeck <linux@roeck-us.net> wrote:
> On 07/06/2018 01:18 AM, Srinath Mannam wrote:
>>
>> Hi Guenter,
>>
>> Thank you very much for your feedback. Please find my comments.
>>
>> On Thu, Jul 5, 2018 at 8:58 PM, Guenter Roeck <linux@roeck-us.net> wrote:
>>>
>>> On 07/04/2018 08:22 PM, Srinath Mannam wrote:
>>>>
>>>>
>>>> When using ACPI node, binding clock devices are
>>>> not available as device tree, So clock-frequency
>>>> property given in _DSD object of ACPI device is
>>>> used to calculate Watchdog rate.
>>>>
>>>> Signed-off-by: Srinath Mannam <srinath.mannam@broadcom.com>
>>>> ---
>>>>    drivers/watchdog/sp805_wdt.c | 29 ++++++++++++++++++++++++-----
>>>>    1 file changed, 24 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/drivers/watchdog/sp805_wdt.c b/drivers/watchdog/sp805_wdt.c
>>>> index 9849db0..d830dbc 100644
>>>> --- a/drivers/watchdog/sp805_wdt.c
>>>> +++ b/drivers/watchdog/sp805_wdt.c
>>>> @@ -22,6 +22,7 @@
>>>>    #include <linux/math64.h>
>>>>    #include <linux/module.h>
>>>>    #include <linux/moduleparam.h>
>>>> +#include <linux/of.h>
>>>>    #include <linux/pm.h>
>>>>    #include <linux/slab.h>
>>>>    #include <linux/spinlock.h>
>>>> @@ -65,6 +66,7 @@ struct sp805_wdt {
>>>>          spinlock_t                      lock;
>>>>          void __iomem                    *base;
>>>>          struct clk                      *clk;
>>>> +       u64                             rate;
>>>>          struct amba_device              *adev;
>>>>          unsigned int                    load_val;
>>>>    };
>>>> @@ -80,7 +82,10 @@ static int wdt_setload(struct watchdog_device *wdd,
>>>> unsigned int timeout)
>>>>          struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
>>>>          u64 load, rate;
>>>>    -     rate = clk_get_rate(wdt->clk);
>>>> +       if (wdt->rate)
>>>> +               rate = wdt->rate;
>>>> +       else
>>>> +               rate = clk_get_rate(wdt->clk);
>>>
>>>
>>>
>>> No. Get the rate once during probe and store it in wdt->rate.
>>
>> clk_get_rate function was called multiple places in the driver.
>> so that we thought, there may be cases where clock rate can change at
>> run-time.
>> That is the reason, I keep clk_get_rate function.
>
>
> This is not an argument. A changing clock rate without notifying the driver
> would be fatal for a watchdog driver, since it would affect the timeout and
> - if the clock rate is increased - result in arbitrary reboots. If that can
> happen with the clock used by this watchdog, some notification would have to
> be implemented to let the driver know.
>
As you said, I will keep wdt->rate and remove the clk_get_rate call. Thank you.
>>>
>>>>          /*
>>>>           * sp805 runs counter with given value twice, after the end of
>>>> first
>>>> @@ -108,7 +113,10 @@ static unsigned int wdt_timeleft(struct
>>>> watchdog_device *wdd)
>>>>          struct sp805_wdt *wdt = watchdog_get_drvdata(wdd);
>>>>          u64 load, rate;
>>>>    -     rate = clk_get_rate(wdt->clk);
>>>> +       if (wdt->rate)
>>>> +               rate = wdt->rate;
>>>> +       else
>>>> +               rate = clk_get_rate(wdt->clk);
>>>
>>>
>>>
>>> Same here.
>>>
>>>>          spin_lock(&wdt->lock);
>>>>          load = readl_relaxed(wdt->base + WDTVALUE);
>>>> @@ -230,11 +238,22 @@ sp805_wdt_probe(struct amba_device *adev, const
>>>> struct amba_id *id)
>>>>          wdt->clk = devm_clk_get(&adev->dev, NULL);
>>>>          if (IS_ERR(wdt->clk)) {
>>>> -               dev_warn(&adev->dev, "Clock not found\n");
>>>> -               ret = PTR_ERR(wdt->clk);
>>>> -               goto err;
>>>> +               dev_warn(&adev->dev, "Clock device not found\n");
>>>
>>>
>>>
>>> "Clock _device_" ? Why this change ? And why retain that warning
>>> unconditionally ?
>>
>> I mean, peripheral may have clock input but clock device node is not
>> available to this driver.
>> So I keep the warning.
>
>
> There is now a warning even though everything is fine, if the clock rate
> is provided with the "clock-frequency" property instead of the documented
> properties. That is unacceptable. I don't want to get flooded with messages
> from people asking what this message is about.
>
>> I thought to handle this better, divide this part of code into two
>> parts based on device tree and ACPI.
>> But this driver implementation is independent of device tree and ACPI
>> calls.
>> To get device-tree properties watch-dog framework APIs are called ex:
>> timeout.
>> Can I add ACPI and device tree node availability check to get clock
>> device and clock-frequency properties. Please advice.
>
>
> Sorry, I fail to parse what you are trying to say.
>
This wdt driver is AMBA framework based driver.
AMBA framework itself expects apb_pclk clock device node from device tree
to enable pclk. So we must add apb_pclk property in device tree node.
For example, In our platform which is based on device tree,
we pass clock nodes to sp805 driver as
                 clocks = <&hsls_25m_div2_clk>, <&hsls_div4_clk>;
                 clock-names = "wdogclk", "apb_pclk";
hsls_div4_clk is abp_pclk, and hsls_25m_div2_clk is wdogclk which is
the first node.
AMBA driver get the clock node using clock_get API with "apb_pclk" string.
In wdt driver clk_get api called with NULL string so first clock node
is taken as its clock node.
few other vendor platforms take same clock for both apb_pclk and wdt clocks.
In that case only one clock node in dt node and clock-name must be
given as apb_pclk.
then the same clock node taken to wdt clock also because wdt driver
call clock_get API with NULL.

So we can't use clock-frequency as alternative to clock nodes in
device tree system.
If we want to use.
we need to pass apb_pclk node and clock-frequency properties in dt node.
In that case apb_pclk node is taken as wdt clock because clk_get API
called with NULL string.
To avoid this, we need to call clk_get function in wdt driver with
valid string instead of NULL
Then clk_get failed and go for clock-frequency property.
If valid string we used for wdt clock in the driver, then it will be
problem for few platforms
where only one clock node used for both apb_pclk and wdt clock.
To solve this we need to pass same clock node for both apb_pclk and wdt clock.
So it causes changes in their DTS files.
I have a different approach to use clock-frequency support in only ACPI systems.
I will push those changes in next patch set.


> Lets summarize: You are introducing a new means for this driver to obtain
> the clock rate used by the watchdog. This is quite independent of the
> instantiation method, since it works for both ACPI and non-ACPI systems.
> This change needs to be documented and approved by devicetree maintainers.
> Its implementation must then accept all valid methods to obtain the clock
> rate without warning or error message.
>
> Thanks,
> Guenter
>
>>>
>>>> +               wdt->clk = NULL;
>>>> +               /*
>>>> +                * When Driver probe with ACPI device, clock devices
>>>> +                * are not available, so watchdog rate get from
>>>> +                * clock-frequency property given in _DSD object.
>>>> +                */
>>>> +               device_property_read_u64(&adev->dev, "clock-frequency",
>>>> +                                        &wdt->rate);
>>>> +               if (!wdt->rate) {
>>>> +                       ret = -ENODEV;
>>>
>>>
>>>
>>> This unconditionally overrides the original error.
>>
>> I accept, I will change.
>>>
>>>
>>>> +                       goto err;
>>>> +               }
>>>>          }
>>>>    +
>>>
>>>
>>>
>>> No whitespace changes, please.
>>
>> I will remove.
>>>
>>>
>>> Does that mean that ACPI doesn't support the clock subsystem and that
>>> each
>>> driver
>>> supporting ACPI must do this ? That would be messy. Also, the above does
>>> not
>>> check
>>> if the device was probed through ACPI. It just tries to find an
>>> undocumented
>>> "clock-frequency" property which is quite different and would apply to
>>> (probably mis-configured) devicetree files as well.
>>>
>>> Either case, I would rather have this addressed through the clock
>>> subsystem.
>>> Otherwise, someone with subject knowledge will have to confirm that this
>>> is
>>> the
>>> appropriate solution. If so, the new property will have to be documented
>>> as
>>> an
>>> alternative to clock specifiers and accepted by devicetree maintainers.
>>>
>> I checked with ACPI maintainers, ACPI does not support common-clock
>> framework and also no plan.
>> AMBA framework also request for "apb_pclk" clock node to enable pclk.
>> But ACPI does not do the same.
>> So in device-tree use case, both apb_pclk and wdt clock nodes are
>> required properties, so passing
>> clock-frequency alone can not be alternative.
>> Because ACPI does not support clk node method, I came up with
>> alternate fixed-clock property clock-frequency.
>> clock-frequency is only specific to ACPI case, so we can't add in
>> binding document.
>> I will add device tree and ACPI specific check to read clock nodes and
>> clock-frequency properties separately.
>>
>> If you are fine with this I will send the next patch with modifications.
>>
>>> Guenter
>>>
>>>>          wdt->adev = adev;
>>>>          wdt->wdd.info = &wdt_info;
>>>>          wdt->wdd.ops = &wdt_ops;
>>>>
>>>
>> Thank you,
>>
>> Regards,
>> Srinath.
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>>
>
Regards,
Srinath.