Subject: [[PATCHv2] 3/3] drivers/rtc/rtc-snvs: Add clock support

From: [email-masked] (Sanchayan Maity)
Date: Thu, 13 Nov 2014 11:03:09 +0530

On Wednesday 12 November 2014 04:17 PM, Shawn Guo wrote:
> On Wed, Nov 12, 2014 at 02:26:51PM +0530, Sanchayan Maity wrote:
>> On Wednesday 12 November 2014 02:57 AM, Stefan Agner wrote:
>>> On 2014-11-07 14:04, 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.
>>>
>>> What happens if the device tree node is there while this patch is not
>>> applied? I guess the driver would load, but since the clocks of the
>>> peripheral are not enabled the first register access would lead to bus
>>> error or similar. If this is the case, this would break bisectability.
>>> You should move the device tree patch to the end.
>>>
>>
>> If the DT node was present with this patch not applied, the driver would 
>> still crash with a bus error, since the clocks for SNVS are not explicitly 
>> enabled anywhere else. I had not thought about any problems which might 
>> occur later with git bisect. Will move this to the end with v3.
> 
> Since changes on rtc-snvs.c will need to go through RTC subsystem tree,
> that means I cannot apply DTS changes until the driver patch gets
> mainlined and appears on my tree.
> 
> Shawn

Shawn

So the approach in this patch is OK and acceptable? 

Since the DT changes cannot be applied by you, till this goes through the 
RTC subsystem tree, gets mainlined and appears on your tree, I will send out 
this patch by itself then and send the DT changes later once this gets
mainlined?

I did not CC Alessandro Zummo, the maintainer of RTC subsystem by mistake.
Once you ACK/OK this i will send out this patch in isolation then or just 
CC Alessandro Zummo.

- Sanchayan

> 
>>
>> Thanks.
>>
>> Regards,
>> Sanchayan.
>>
>>> Other than that
>>> Acked-by: Stefan Agner <[email-masked]>
>>>
>>> --
>>> Stefan
>>>
>>>>
>>>> Signed-off-by: Sanchayan Maity <[email-masked]>
>>>> ---
>>>>  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
>>>