Commit f6a46f8b authored by Alexandre Belloni's avatar Alexandre Belloni
Browse files

rtc: at91rm9200: add correction support 



The sama5d4 and sama5d2 RTCs are able to correct for imprecise crystals, up
to 1953 ppm.

Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: default avatarNicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20201108232001.1580128-1-alexandre.belloni@bootlin.com
parent 767fbb71

drivers/rtc/rtc-at91rm9200.c

+99 −4
Original line number Diff line number Diff line
@@ -36,6 +36,10 @@ 
#define		AT91_RTC_UPDCAL		BIT(1)		/* Update Request Calendar Register */



#define	AT91_RTC_MR		0x04			/* Mode Register */

#define		AT91_RTC_HRMOD		BIT(0)		/* 12/24 hour mode */

#define		AT91_RTC_NEGPPM		BIT(4)		/* Negative PPM correction */

#define		AT91_RTC_CORRECTION	GENMASK(14, 8)	/* Slow clock correction */

#define		AT91_RTC_HIGHPPM	BIT(15)		/* High PPM correction */



#define	AT91_RTC_TIMR		0x08			/* Time Register */

#define		AT91_RTC_SEC		GENMASK(6, 0)	/* Current Second */
@@ -77,6 +81,9 @@ 
#define		AT91_RTC_NVTIMALR	BIT(2)		/* Non valid Time Alarm */

#define		AT91_RTC_NVCALALR	BIT(3)		/* Non valid Calendar Alarm */



#define AT91_RTC_CORR_DIVIDEND		3906000

#define AT91_RTC_CORR_LOW_RATIO		20



#define at91_rtc_read(field) \

	readl_relaxed(at91_rtc_regs + field)

#define at91_rtc_write(field, val) \
@@ -84,6 +91,7 @@ 


struct at91_rtc_config {

	bool use_shadow_imr;

	bool has_correction;

};



static const struct at91_rtc_config *at91_rtc_config;
@@ -293,6 +301,75 @@ static int at91_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled) 
	return 0;

}



static int at91_rtc_readoffset(struct device *dev, long *offset)

{

	u32 mr = at91_rtc_read(AT91_RTC_MR);

	long val = FIELD_GET(AT91_RTC_CORRECTION, mr);



	if (!val) {

		*offset = 0;

		return 0;

	}



	val++;



	if (!(mr & AT91_RTC_NEGPPM))

		val = -val;



	if (!(mr & AT91_RTC_HIGHPPM))

		val *= AT91_RTC_CORR_LOW_RATIO;



	*offset = DIV_ROUND_CLOSEST(AT91_RTC_CORR_DIVIDEND, val);



	return 0;

}



static int at91_rtc_setoffset(struct device *dev, long offset)

{

	long corr;

	u32 mr;



	if (offset > AT91_RTC_CORR_DIVIDEND / 2)

		return -ERANGE;

	if (offset < -AT91_RTC_CORR_DIVIDEND / 2)

		return -ERANGE;



	mr = at91_rtc_read(AT91_RTC_MR);

	mr &= ~(AT91_RTC_NEGPPM | AT91_RTC_CORRECTION | AT91_RTC_HIGHPPM);



	if (offset > 0)

		mr |= AT91_RTC_NEGPPM;

	else

		offset = -offset;



	/* offset less than 764 ppb, disable correction*/

	if (offset < 764) {

		at91_rtc_write(AT91_RTC_MR, mr & ~AT91_RTC_NEGPPM);



		return 0;

	}



	/*

	 * 29208 ppb is the perfect cutoff between low range and high range

	 * low range values are never better than high range value after that.

	 */

	if (offset < 29208) {

		corr = DIV_ROUND_CLOSEST(AT91_RTC_CORR_DIVIDEND, offset * AT91_RTC_CORR_LOW_RATIO);

	} else {

		corr = DIV_ROUND_CLOSEST(AT91_RTC_CORR_DIVIDEND, offset);

		mr |= AT91_RTC_HIGHPPM;

	}



	if (corr > 128)

		corr = 128;



	mr |= FIELD_PREP(AT91_RTC_CORRECTION, corr - 1);



	at91_rtc_write(AT91_RTC_MR, mr);



	return 0;

}



/*

 * IRQ handler for the RTC

 */
@@ -343,6 +420,10 @@ static const struct at91_rtc_config at91sam9x5_config = { 
	.use_shadow_imr	= true,

};



static const struct at91_rtc_config sama5d4_config = {

	.has_correction = true,

};



static const struct of_device_id at91_rtc_dt_ids[] = {

	{

		.compatible = "atmel,at91rm9200-rtc",
@@ -352,10 +433,10 @@ static const struct of_device_id at91_rtc_dt_ids[] = { 
		.data = &at91sam9x5_config,

	}, {

		.compatible = "atmel,sama5d4-rtc",

		.data = &at91rm9200_config,

		.data = &sama5d4_config,

	}, {

		.compatible = "atmel,sama5d2-rtc",

		.data = &at91rm9200_config,

		.data = &sama5d4_config,

	}, {

		/* sentinel */

	}
@@ -370,6 +451,16 @@ static const struct rtc_class_ops at91_rtc_ops = { 
	.alarm_irq_enable = at91_rtc_alarm_irq_enable,

};



static const struct rtc_class_ops sama5d4_rtc_ops = {

	.read_time	= at91_rtc_readtime,

	.set_time	= at91_rtc_settime,

	.read_alarm	= at91_rtc_readalarm,

	.set_alarm	= at91_rtc_setalarm,

	.alarm_irq_enable = at91_rtc_alarm_irq_enable,

	.set_offset	= at91_rtc_setoffset,

	.read_offset	= at91_rtc_readoffset,

};



/*

 * Initialize and install RTC driver

 */
@@ -416,7 +507,7 @@ static int __init at91_rtc_probe(struct platform_device *pdev) 
	}



	at91_rtc_write(AT91_RTC_CR, 0);

	at91_rtc_write(AT91_RTC_MR, 0);		/* 24 hour mode */

	at91_rtc_write(AT91_RTC_MR, at91_rtc_read(AT91_RTC_MR) & ~AT91_RTC_HRMOD);



	/* Disable all interrupts */

	at91_rtc_write_idr(AT91_RTC_ACKUPD | AT91_RTC_ALARM |
@@ -437,7 +528,11 @@ static int __init at91_rtc_probe(struct platform_device *pdev) 
	if (!device_can_wakeup(&pdev->dev))

		device_init_wakeup(&pdev->dev, 1);



	if (at91_rtc_config->has_correction)

		rtc->ops = &sama5d4_rtc_ops;

	else

		rtc->ops = &at91_rtc_ops;



	rtc->range_min = RTC_TIMESTAMP_BEGIN_1900;

	rtc->range_max = RTC_TIMESTAMP_END_2099;

	ret = rtc_register_device(rtc);