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Commit 7fe8fcee authored by Alexandre Belloni's avatar Alexandre Belloni
Browse files

rtc: jz4740: rework invalid time detection 



The scratchpad register is used to detect an invalid time when power to the
RTC has been lost. Instead of deleting that precious information and set
the time to the UNIX epoch, forward it to userspace.

Tested-by: default avatarMathieu Malaterre <malat@debian.org>
Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@bootlin.com>
parent 3b2dc19f

drivers/rtc/rtc-jz4740.c

+9 −12
Original line number Diff line number Diff line
@@ -157,6 +157,9 @@ static int jz4740_rtc_read_time(struct device *dev, struct rtc_time *time) 
	uint32_t secs, secs2;

	int timeout = 5;



	if (jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SCRATCHPAD) != 0x12345678)

		return -EINVAL;



	/* If the seconds register is read while it is updated, it can contain a

	 * bogus value. This can be avoided by making sure that two consecutive

	 * reads have the same value.
@@ -180,8 +183,13 @@ static int jz4740_rtc_read_time(struct device *dev, struct rtc_time *time) 
static int jz4740_rtc_set_time(struct device *dev, struct rtc_time *time)

{

	struct jz4740_rtc *rtc = dev_get_drvdata(dev);

	int ret;



	return jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SEC, rtc_tm_to_time64(time));

	ret = jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SEC, rtc_tm_to_time64(time));

	if (ret)

		return ret;



	return jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SCRATCHPAD, 0x12345678);

}



static int jz4740_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
@@ -308,7 +316,6 @@ static int jz4740_rtc_probe(struct platform_device *pdev) 
{

	int ret;

	struct jz4740_rtc *rtc;

	uint32_t scratchpad;

	struct resource *mem;

	const struct platform_device_id *id = platform_get_device_id(pdev);

	const struct of_device_id *of_id = of_match_device(
@@ -376,16 +383,6 @@ static int jz4740_rtc_probe(struct platform_device *pdev) 
		return ret;

	}



	scratchpad = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SCRATCHPAD);

	if (scratchpad != 0x12345678) {

		ret = jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SCRATCHPAD, 0x12345678);

		ret = jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SEC, 0);

		if (ret) {

			dev_err(&pdev->dev, "Could not write to RTC registers\n");

			return ret;

		}

	}



	if (np && of_device_is_system_power_controller(np)) {

		if (!pm_power_off) {

			/* Default: 60ms */