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

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Date:   Wed, 3 May 2017 11:39:34 +0530
From:   Keerthy <j-keerthy@...com>
To:     <a.zummo@...ertech.it>, <alexandre.belloni@...e-electrons.com>
CC:     <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 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

> 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);
>