[RESEND PATCHv2] Add SNVS clock support to rtc-snvs driver

[RESEND PATCHv2] Add SNVS clock support to rtc-snvs driver

[Sanchayan Maity]

For v2:
As such this patch remains the same, but is being resend
and in isolation after the previous discussions here.
https://lkml.org/lkml/2014/11/7/295

Since the changes on rtc-snvs.c will need to go through
the rtc subsystem tree and the DT changes cannot be applied
by Shawn, till this driver patch gets mainlined, this driver
patch I am sending by itself without the DT changes send
earlier.

The first version of the patches were send quiet a 
while back. 
https://lkml.org/lkml/2014/9/26/492

The reason for sending this v2 of the patches late was to
prevent any changes midway to the VF dts patches being tried
with the below commit.
https://lkml.org/lkml/2014/10/22/605

Changes since v1:
The clock enable and disable functions for the SNVS are
now optional and only enable/disable it, if it has been
defined in the device tree node. Instead of failing and 
returning error as in the earlier set of patches, this
makes sure that the driver does not break for the other
i.MX devices for which the clock has not been defined and
enabled elsewhere.

Sanchayan Maity (1):
  drivers/rtc/rtc-snvs: Add clock support

 drivers/rtc/rtc-snvs.c |   34 ++++++++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

-- 
1.7.9.5

[RESEND PATCHv2] drivers/rtc/rtc-snvs: Add clock support

[Sanchayan Maity]

This patch adds clock enable and disable support for
the SNVS peripheral, which is required for using the
RTC within the SNVS block.

The clock is not strictly enforced, as this would
break the i.MX devices. The clocking for the i.MX
devices seems to be enabled elsewhere and enabling
RTC SNVS for Vybrid results in a crash. This patch
adds the clock support but also makes it optional
so Vybrid platform can use the clock if defined
while making sure not to break i.MX .

Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
---
 drivers/rtc/rtc-snvs.c |   34 ++++++++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/drivers/rtc/rtc-snvs.c b/drivers/rtc/rtc-snvs.c
index fa384fe..d4a6512 100644
--- a/drivers/rtc/rtc-snvs.c
+++ b/drivers/rtc/rtc-snvs.c
@@ -17,6 +17,7 @@
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/rtc.h>
+#include <linux/clk.h>
 
 /* These register offsets are relative to LP (Low Power) range */
 #define SNVS_LPCR		0x04
@@ -39,6 +40,7 @@ struct snvs_rtc_data {
 	void __iomem *ioaddr;
 	int irq;
 	spinlock_t lock;
+	struct clk *clk;
 };
 
 static u32 rtc_read_lp_counter(void __iomem *ioaddr)
@@ -260,6 +262,18 @@ static int snvs_rtc_probe(struct platform_device *pdev)
 	if (data->irq < 0)
 		return data->irq;
 
+	data->clk = devm_clk_get(&pdev->dev, "snvs-rtc");
+	if (IS_ERR(data->clk)) {
+		data->clk = NULL;
+	} else {
+		ret = clk_prepare_enable(data->clk);
+		if (ret) {
+			dev_err(&pdev->dev,
+				"Could not prepare or enable the snvs clock\n");
+			return ret;
+		}
+	}
+
 	platform_set_drvdata(pdev, data);
 
 	spin_lock_init(&data->lock);
@@ -280,7 +294,7 @@ static int snvs_rtc_probe(struct platform_device *pdev)
 	if (ret) {
 		dev_err(&pdev->dev, "failed to request irq %d: %d\n",
 			data->irq, ret);
-		return ret;
+		goto error_rtc_device_register;
 	}
 
 	data->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
@@ -288,10 +302,16 @@ static int snvs_rtc_probe(struct platform_device *pdev)
 	if (IS_ERR(data->rtc)) {
 		ret = PTR_ERR(data->rtc);
 		dev_err(&pdev->dev, "failed to register rtc: %d\n", ret);
-		return ret;
+		goto error_rtc_device_register;
 	}
 
 	return 0;
+
+error_rtc_device_register:
+	if (data->clk)
+		clk_disable_unprepare(data->clk);
+
+	return ret;
 }
 
 #ifdef CONFIG_PM_SLEEP
@@ -302,16 +322,26 @@ static int snvs_rtc_suspend(struct device *dev)
 	if (device_may_wakeup(dev))
 		enable_irq_wake(data->irq);
 
+	if (data->clk)
+		clk_disable_unprepare(data->clk);
+
 	return 0;
 }
 
 static int snvs_rtc_resume(struct device *dev)
 {
 	struct snvs_rtc_data *data = dev_get_drvdata(dev);
+	int ret;
 
 	if (device_may_wakeup(dev))
 		disable_irq_wake(data->irq);
 
+	if (data->clk) {
+		ret = clk_prepare_enable(data->clk);
+		if (ret)
+			return ret;
+	}
+
 	return 0;
 }
 #endif
-- 
1.7.9.5

Re: [RESEND PATCHv2] drivers/rtc/rtc-snvs: Add clock support

[Stefan Agner]

On 2014-12-03 06:58, Sanchayan Maity wrote:
> This patch adds clock enable and disable support for
> the SNVS peripheral, which is required for using the
> RTC within the SNVS block.
> 
> The clock is not strictly enforced, as this would
> break the i.MX devices. The clocking for the i.MX
> devices seems to be enabled elsewhere and enabling
> RTC SNVS for Vybrid results in a crash. This patch
> adds the clock support but also makes it optional
> so Vybrid platform can use the clock if defined
> while making sure not to break i.MX .
> 
> Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
> ---
>  drivers/rtc/rtc-snvs.c |   34 ++++++++++++++++++++++++++++++++--
>  1 file changed, 32 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-snvs.c b/drivers/rtc/rtc-snvs.c
> index fa384fe..d4a6512 100644
> --- a/drivers/rtc/rtc-snvs.c
> +++ b/drivers/rtc/rtc-snvs.c
> @@ -17,6 +17,7 @@
>  #include <linux/of_device.h>
>  #include <linux/platform_device.h>
>  #include <linux/rtc.h>
> +#include <linux/clk.h>
>  
>  /* These register offsets are relative to LP (Low Power) range */
>  #define SNVS_LPCR		0x04
> @@ -39,6 +40,7 @@ struct snvs_rtc_data {
>  	void __iomem *ioaddr;
>  	int irq;
>  	spinlock_t lock;
> +	struct clk *clk;
>  };
>  
>  static u32 rtc_read_lp_counter(void __iomem *ioaddr)
> @@ -260,6 +262,18 @@ static int snvs_rtc_probe(struct platform_device *pdev)
>  	if (data->irq < 0)
>  		return data->irq;
>  
> +	data->clk = devm_clk_get(&pdev->dev, "snvs-rtc");
> +	if (IS_ERR(data->clk)) {
> +		data->clk = NULL;
> +	} else {
> +		ret = clk_prepare_enable(data->clk);
> +		if (ret) {
> +			dev_err(&pdev->dev,
> +				"Could not prepare or enable the snvs clock\n");
> +			return ret;
> +		}
> +	}
> +
>  	platform_set_drvdata(pdev, data);
>  
>  	spin_lock_init(&data->lock);
> @@ -280,7 +294,7 @@ static int snvs_rtc_probe(struct platform_device *pdev)
>  	if (ret) {
>  		dev_err(&pdev->dev, "failed to request irq %d: %d\n",
>  			data->irq, ret);
> -		return ret;
> +		goto error_rtc_device_register;
>  	}
>  
>  	data->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
> @@ -288,10 +302,16 @@ static int snvs_rtc_probe(struct platform_device *pdev)
>  	if (IS_ERR(data->rtc)) {
>  		ret = PTR_ERR(data->rtc);
>  		dev_err(&pdev->dev, "failed to register rtc: %d\n", ret);
> -		return ret;
> +		goto error_rtc_device_register;
>  	}
>  
>  	return 0;
> +
> +error_rtc_device_register:
> +	if (data->clk)
> +		clk_disable_unprepare(data->clk);
> +
> +	return ret;
>  }
>  
>  #ifdef CONFIG_PM_SLEEP
> @@ -302,16 +322,26 @@ static int snvs_rtc_suspend(struct device *dev)
>  	if (device_may_wakeup(dev))
>  		enable_irq_wake(data->irq);
>  
> +	if (data->clk)
> +		clk_disable_unprepare(data->clk);
> +
>  	return 0;
>  }
>  
>  static int snvs_rtc_resume(struct device *dev)
>  {
>  	struct snvs_rtc_data *data = dev_get_drvdata(dev);
> +	int ret;
>  
>  	if (device_may_wakeup(dev))
>  		disable_irq_wake(data->irq);
>  
> +	if (data->clk) {
> +		ret = clk_prepare_enable(data->clk);
> +		if (ret)
> +			return ret;
> +	}
> +
>  	return 0;
>  }
>  #endif


Acked-by: Stefan Agner <stefan@agner.ch>

--
Stefan

Re: [RESEND PATCHv2] drivers/rtc/rtc-snvs: Add clock support

[Alessandro Zummo]

On Wed,  3 Dec 2014 11:28:55 +0530
Sanchayan Maity <maitysanchayan@gmail.com> wrote:

> The clock is not strictly enforced, as this would
> break the i.MX devices. The clocking for the i.MX
> devices seems to be enabled elsewhere and enabling
> RTC SNVS for Vybrid results in a crash. This patch
> adds the clock support but also makes it optional
> so Vybrid platform can use the clock if defined
> while making sure not to break i.MX .
> 
> Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>


 Acked-by: Alessandro Zummo <a.zummo@towertech.it>

-- 

 Best regards,

 Alessandro Zummo,
  Tower Technologies - Torino, Italy

  http://www.towertech.it

Re: [RESEND PATCHv2] drivers/rtc/rtc-snvs: Add clock support

[Stefan Agner]

On 2014-12-04 11:05, Alessandro Zummo wrote:
> On Wed,  3 Dec 2014 11:28:55 +0530
> Sanchayan Maity <maitysanchayan@gmail.com> wrote:
> 
>> The clock is not strictly enforced, as this would
>> break the i.MX devices. The clocking for the i.MX
>> devices seems to be enabled elsewhere and enabling
>> RTC SNVS for Vybrid results in a crash. This patch
>> adds the clock support but also makes it optional
>> so Vybrid platform can use the clock if defined
>> while making sure not to break i.MX .
>>
>> Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
> 
> 
>  Acked-by: Alessandro Zummo <a.zummo@towertech.it>

Through which tree is this going upstream?

--
Stefan

Re: [RESEND PATCHv2] drivers/rtc/rtc-snvs: Add clock support

[Alessandro Zummo]

On Thu, 04 Dec 2014 13:29:58 +0100
Stefan Agner <stefan@agner.ch> wrote:

> >  Acked-by: Alessandro Zummo <a.zummo@towertech.it>  
> 
> Through which tree is this going upstream?

 Andrew usually picks up those small patches, unless there's
 a more appropriate tree.
 

-- 

 Best regards,

 Alessandro Zummo,
  Tower Technologies - Torino, Italy

  http://www.towertech.it

Re: [RESEND PATCHv2] drivers/rtc/rtc-snvs: Add clock support

[Andrew Morton]

On Wed,  3 Dec 2014 11:28:55 +0530 Sanchayan Maity <maitysanchayan@gmail.com> wrote:

> This patch adds clock enable and disable support for
> the SNVS peripheral, which is required for using the
> RTC within the SNVS block.
> 
> The clock is not strictly enforced, as this would
> break the i.MX devices. The clocking for the i.MX
> devices seems to be enabled elsewhere and enabling
> RTC SNVS for Vybrid results in a crash. This patch
> adds the clock support but also makes it optional
> so Vybrid platform can use the clock if defined
> while making sure not to break i.MX .
> 
> ...

I assume this hasn't been tested with CONFIG_HAVE_CLK=n.  It all
*looks* OK, but the clk API does its tests for clk==NULL in some very
deep places.

> --- a/drivers/rtc/rtc-snvs.c
> +++ b/drivers/rtc/rtc-snvs.c
.
> ...
>
> @@ -288,10 +302,16 @@ static int snvs_rtc_probe(struct platform_device *pdev)
>  	if (IS_ERR(data->rtc)) {
>  		ret = PTR_ERR(data->rtc);
>  		dev_err(&pdev->dev, "failed to register rtc: %d\n", ret);
> -		return ret;
> +		goto error_rtc_device_register;
>  	}
>  
>  	return 0;
> +
> +error_rtc_device_register:
> +	if (data->clk)
> +		clk_disable_unprepare(data->clk);

>From my reading, there's no need to test data->clk here -
clk_disable_unprepare() handles that.

It doesn't hurt to test it - a reasonable approach would be to look
around at what other users of the clk API are doing, and do that.


> +	return ret;
>  }
>  
>  #ifdef CONFIG_PM_SLEEP
> @@ -302,16 +322,26 @@ static int snvs_rtc_suspend(struct device *dev)
>  	if (device_may_wakeup(dev))
>  		enable_irq_wake(data->irq);
>  
> +	if (data->clk)
> +		clk_disable_unprepare(data->clk);

Ditto.

>  	return 0;
>  }
>  
>  static int snvs_rtc_resume(struct device *dev)
>  {
>  	struct snvs_rtc_data *data = dev_get_drvdata(dev);
> +	int ret;
>  
>  	if (device_may_wakeup(dev))
>  		disable_irq_wake(data->irq);
>  
> +	if (data->clk) {
> +		ret = clk_prepare_enable(data->clk);
> +		if (ret)
> +			return ret;
> +	}

It could be omitted here also.

>  	return 0;
>  }
>  #endif

Re: [RESEND PATCHv2] drivers/rtc/rtc-snvs: Add clock support

[Stefan Agner]

On 2014-12-05 01:12, Andrew Morton wrote:
> On Wed,  3 Dec 2014 11:28:55 +0530 Sanchayan Maity
> <maitysanchayan@gmail.com> wrote:
> 
>> This patch adds clock enable and disable support for
>> the SNVS peripheral, which is required for using the
>> RTC within the SNVS block.
>>
>> The clock is not strictly enforced, as this would
>> break the i.MX devices. The clocking for the i.MX
>> devices seems to be enabled elsewhere and enabling
>> RTC SNVS for Vybrid results in a crash. This patch
>> adds the clock support but also makes it optional
>> so Vybrid platform can use the clock if defined
>> while making sure not to break i.MX .
>>
>> ...
> 
> I assume this hasn't been tested with CONFIG_HAVE_CLK=n.  It all
> *looks* OK, but the clk API does its tests for clk==NULL in some very
> deep places.
> 
>> --- a/drivers/rtc/rtc-snvs.c
>> +++ b/drivers/rtc/rtc-snvs.c
> .
>> ...
>>
>> @@ -288,10 +302,16 @@ static int snvs_rtc_probe(struct platform_device *pdev)
>>  	if (IS_ERR(data->rtc)) {
>>  		ret = PTR_ERR(data->rtc);
>>  		dev_err(&pdev->dev, "failed to register rtc: %d\n", ret);
>> -		return ret;
>> +		goto error_rtc_device_register;
>>  	}
>>
>>  	return 0;
>> +
>> +error_rtc_device_register:
>> +	if (data->clk)
>> +		clk_disable_unprepare(data->clk);
> 
> From my reading, there's no need to test data->clk here -
> clk_disable_unprepare() handles that.
> 
> It doesn't hurt to test it - a reasonable approach would be to look
> around at what other users of the clk API are doing, and do that.
> 
> 
>> +	return ret;
>>  }
>>
>>  #ifdef CONFIG_PM_SLEEP
>> @@ -302,16 +322,26 @@ static int snvs_rtc_suspend(struct device *dev)
>>  	if (device_may_wakeup(dev))
>>  		enable_irq_wake(data->irq);
>>
>> +	if (data->clk)
>> +		clk_disable_unprepare(data->clk);
> 
> Ditto.
> 
>>  	return 0;
>>  }
>>
>>  static int snvs_rtc_resume(struct device *dev)
>>  {
>>  	struct snvs_rtc_data *data = dev_get_drvdata(dev);
>> +	int ret;
>>
>>  	if (device_may_wakeup(dev))
>>  		disable_irq_wake(data->irq);
>>
>> +	if (data->clk) {
>> +		ret = clk_prepare_enable(data->clk);
>> +		if (ret)
>> +			return ret;
>> +	}
> 

Just discovered issue with suspend/resume I am testing right now: The
alarm interrupt handler also reads registers which are part of SNVS and
need clocks enabled. However, the resume function is called after IRQ's
have been enabled, hence this leads to a abort:

[   90.755222] Unhandled fault: external abort on non-linefetch (0x1008)
at 0x908c604c
[   90.762892] Internal error: : 1008 [#1] ARM
[   90.767082] Modules linked in:
[   90.770174] CPU: 0 PID: 421 Comm: sh Not tainted
3.18.0-rc5-00135-g0689c67-dirty #1592
[   90.778100] task: 8e03e800 ti: 8cad8000 task.ti: 8cad8000
[   90.783530] PC is at snvs_rtc_irq_handler+0x14/0x74
[   90.788424] LR is at handle_irq_event_percpu+0x3c/0x144

It can be fixed, with something like this:

@@ -346,7 +347,10 @@ static int snvs_rtc_resume(struct device *dev)
 }
 #endif
 
-static SIMPLE_DEV_PM_OPS(snvs_rtc_pm_ops, snvs_rtc_suspend,
snvs_rtc_resume);
+static const struct dev_pm_ops snvs_rtc_pm_ops = {
+       .suspend_noirq = snvs_rtc_suspend,
+       .resume_noirq = snvs_rtc_resume,
+};
 
 static const struct of_device_id snvs_dt_ids[] = {
        { .compatible = "fsl,sec-v4.0-mon-rtc-lp", },



Andrew, this patch is already merged, so it would need another fix for
this, right?

--
Stefan

> It could be omitted here also.
> 
>>  	return 0;
>>  }
>>  #endif

Re: [RESEND PATCHv2] drivers/rtc/rtc-snvs: Add clock support

[Andrew Morton]

On Fri, 05 Dec 2014 15:54:15 +0100 Stefan Agner <stefan@agner.ch> wrote:

> It can be fixed, with something like this:
> 
> @@ -346,7 +347,10 @@ static int snvs_rtc_resume(struct device *dev)
>  }
>  #endif
>  
> -static SIMPLE_DEV_PM_OPS(snvs_rtc_pm_ops, snvs_rtc_suspend,
> snvs_rtc_resume);
> +static const struct dev_pm_ops snvs_rtc_pm_ops = {
> +       .suspend_noirq = snvs_rtc_suspend,
> +       .resume_noirq = snvs_rtc_resume,
> +};
>  
>  static const struct of_device_id snvs_dt_ids[] = {
>         { .compatible = "fsl,sec-v4.0-mon-rtc-lp", },
> 
> 
> 
> Andrew, this patch is already merged, so it would need another fix for
> this, right?

A replacement patch is OK.  An incremental patch is OK too.  I almost
always turn the replacement into an incremental so that I and others
can see what changed.