linux-kernel - Re: [PATCH] RTC: Add functionality to read/write rtc scratch registers

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Message-ID: <48ad1d72-e007-b453-78c2-5a1fec8ec8e5@ti.com>
Date:   Fri, 5 May 2017 09:01:08 +0530
From:   Keerthy <j-keerthy@...com>
To:     Alexandre Belloni <alexandre.belloni@...e-electrons.com>
CC:     <a.zummo@...ertech.it>, <rtc-linux@...glegroups.com>,
        <linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
        Russ Dill <Russ.Dill@...com>
Subject: Re: [PATCH] RTC: Add functionality to read/write rtc scratch
 registers



On Friday 05 May 2017 04:08 AM, Alexandre Belloni wrote:
> Hi,
> 
> On 03/05/2017 at 11:39:34 +0530, Keerthy wrote:
>> On Tuesday 18 April 2017 10:50 AM, Keerthy wrote:
>>> From: Russ Dill <Russ.Dill@...com>
>>>
>>> Many RTCs provide scratch registers that are maintained so long as the RTC
>>> has power. Provide a generic method to access these registers.
>>>
>>
>> A gentle ping on this
>>
> 
> Yeah, I apologize for the delay (I know you already sent this 6-8 months
> ago).
> I'm not satisfied with the interface (and its name). I gave a lot of
> thought into it and I'm currently reworking part of the subsystem to
> create a similar feature. I'm planning to have it in 4.13.

Okay then i will wait for that. Thanks for the response.

> 
>>> Signed-off-by: Russ Dill <Russ.Dill@...com>
>>> Signed-off-by: Keerthy <j-keerthy@...com>
>>> ---
>>>  drivers/rtc/interface.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++++
>>>  drivers/rtc/rtc-omap.c  | 35 ++++++++++++++++++++++++++++++++++
>>>  include/linux/rtc.h     |  7 +++++++
>>>  3 files changed, 92 insertions(+)
>>>
>>> diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
>>> index fc0fa75..facde06 100644
>>> --- a/drivers/rtc/interface.c
>>> +++ b/drivers/rtc/interface.c
>>> @@ -1016,3 +1016,53 @@ int rtc_set_offset(struct rtc_device *rtc, long offset)
>>>  	mutex_unlock(&rtc->ops_lock);
>>>  	return ret;
>>>  }
>>> +
>>> +/* rtc_read_scratch - Read from RTC scratch register
>>> + * @ rtc: rtc device to be used
>>> + * @ index: index of scratch register
>>> + * @ value: returned value read
>>> + *
>>> + * Kernel interface read from an RTC scratch register
>>> + */
>>> +int rtc_read_scratch(struct rtc_device *rtc, unsigned int index, u32 *value)
>>> +{
>>> +	int err;
>>> +
>>> +	mutex_lock(&rtc->ops_lock);
>>> +	if (!rtc->ops)
>>> +		err = -ENODEV;
>>> +	else if (index >= rtc->ops->scratch_size || !rtc->ops->read_scratch)
>>> +		err = -EINVAL;
>>> +	else
>>> +		err = rtc->ops->read_scratch(rtc->dev.parent, index, value);
>>> +	mutex_unlock(&rtc->ops_lock);
>>> +	return err;
>>> +}
>>> +EXPORT_SYMBOL_GPL(rtc_read_scratch);
>>> +
>>> +/* rtc_write_scratch - Write to RTC scratch register
>>> + * @ rtc: rtc device to be used
>>> + * @ index: index of scratch register
>>> + * @ value: value to write
>>> + *
>>> + * Kernel interface write to an RTC scratch register
>>> + */
>>> +int rtc_write_scratch(struct rtc_device *rtc, unsigned int index, u32 value)
>>> +{
>>> +	int err;
>>> +
>>> +	mutex_lock(&rtc->ops_lock);
>>> +
>>> +	if (!rtc->ops)
>>> +		err = -ENODEV;
>>> +	else if (index >= rtc->ops->scratch_size ||
>>> +		 !rtc->ops->write_scratch)
>>> +		err = -EINVAL;
>>> +	else
>>> +		err = rtc->ops->write_scratch(rtc->dev.parent, index, value);
>>> +
>>> +	mutex_unlock(&rtc->ops_lock);
>>> +
>>> +	return err;
>>> +}
>>> +EXPORT_SYMBOL_GPL(rtc_write_scratch);
>>> diff --git a/drivers/rtc/rtc-omap.c b/drivers/rtc/rtc-omap.c
>>> index 13f7cd1..c90d93e 100644
>>> --- a/drivers/rtc/rtc-omap.c
>>> +++ b/drivers/rtc/rtc-omap.c
>>> @@ -70,6 +70,10 @@
>>>  #define OMAP_RTC_COMP_MSB_REG		0x50
>>>  #define OMAP_RTC_OSC_REG		0x54
>>>  
>>> +#define OMAP_RTC_SCRATCH0_REG		0x60
>>> +#define OMAP_RTC_SCRATCH1_REG		0x64
>>> +#define OMAP_RTC_SCRATCH2_REG		0x68
>>> +
>>>  #define OMAP_RTC_KICK0_REG		0x6c
>>>  #define OMAP_RTC_KICK1_REG		0x70
>>>  
>>> @@ -414,6 +418,34 @@ static int omap_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
>>>  
>>>  static struct omap_rtc *omap_rtc_power_off_rtc;
>>>  
>>> +static const u32 omap_rtc_scratch_regs[] = {
>>> +	OMAP_RTC_SCRATCH0_REG,
>>> +	OMAP_RTC_SCRATCH1_REG,
>>> +	OMAP_RTC_SCRATCH2_REG,
>>> +};
>>> +
>>> +static int omap_rtc_read_scratch(struct device *dev, unsigned int index,
>>> +				 u32 *value)
>>> +{
>>> +	*value = readl(omap_rtc_power_off_rtc->base +
>>> +		       omap_rtc_scratch_regs[index]);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int omap_rtc_write_scratch(struct device *dev, unsigned int index,
>>> +				  u32 value)
>>> +{
>>> +	struct omap_rtc *rtc = dev_get_drvdata(dev);
>>> +
>>> +	rtc->type->unlock(rtc);
>>> +	writel(value, omap_rtc_power_off_rtc->base +
>>> +	       omap_rtc_scratch_regs[index]);
>>> +	rtc->type->lock(rtc);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>>  /*
>>>   * omap_rtc_poweroff: RTC-controlled power off
>>>   *
>>> @@ -484,6 +516,9 @@ static void omap_rtc_power_off(void)
>>>  	.read_alarm	= omap_rtc_read_alarm,
>>>  	.set_alarm	= omap_rtc_set_alarm,
>>>  	.alarm_irq_enable = omap_rtc_alarm_irq_enable,
>>> +	.read_scratch	= omap_rtc_read_scratch,
>>> +	.write_scratch	= omap_rtc_write_scratch,
>>> +	.scratch_size	= ARRAY_SIZE(omap_rtc_scratch_regs),
>>>  };
>>>  
>>>  static const struct omap_rtc_device_type omap_rtc_default_type = {
>>> diff --git a/include/linux/rtc.h b/include/linux/rtc.h
>>> index b693ada..da5e003 100644
>>> --- a/include/linux/rtc.h
>>> +++ b/include/linux/rtc.h
>>> @@ -91,6 +91,10 @@ struct rtc_class_ops {
>>>  	int (*alarm_irq_enable)(struct device *, unsigned int enabled);
>>>  	int (*read_offset)(struct device *, long *offset);
>>>  	int (*set_offset)(struct device *, long offset);
>>> +	int (*read_scratch)(struct device *, unsigned int, u32*);
>>> +	int (*write_scratch)(struct device *, unsigned int, u32);
>>> +
>>> +	unsigned int scratch_size;
>>>  };
>>>  
>>>  #define RTC_DEVICE_NAME_SIZE 20
>>> @@ -214,6 +218,9 @@ int rtc_timer_start(struct rtc_device *rtc, struct rtc_timer *timer,
>>>  int rtc_set_offset(struct rtc_device *rtc, long offset);
>>>  void rtc_timer_do_work(struct work_struct *work);
>>>  
>>> +int rtc_read_scratch(struct rtc_device *rtc, unsigned int index, u32 *value);
>>> +int rtc_write_scratch(struct rtc_device *rtc, unsigned int index, u32 value);
>>> +
>>>  static inline bool is_leap_year(unsigned int year)
>>>  {
>>>  	return (!(year % 4) && (year % 100)) || !(year % 400);
>>>
>