linux-kernel - Re: [[PATCHv2] 3/3] drivers/rtc/rtc-snvs: Add clock support

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Message-ID: <546320D3.2030501@gmail.com>
Date:	Wed, 12 Nov 2014 14:26:51 +0530
From:	Sanchayan Maity <maitysanchayan@...il.com>
To:	Stefan Agner <stefan@...er.ch>
CC:	rtc-linux@...glegroups.com, shawn.guo@...aro.org,
	linux@....linux.org.uk, kernel@...gutronix.de,
	b35083@...escale.com, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [[PATCHv2] 3/3] drivers/rtc/rtc-snvs: Add clock support

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.

Thanks.

Regards,
Sanchayan.

> Other than that
> Acked-by: Stefan Agner <stefan@...er.ch>
> 
> --
> Stefan
> 
>>
>> Signed-off-by: Sanchayan Maity <maitysanchayan@...il.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
> 
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