linux-kernel - [PATCH V2] rtc: max8907: weekday encoding fixes

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Message-Id: <1389720189-7832-1-git-send-email-swarren@wwwdotorg.org>
Date:	Tue, 14 Jan 2014 10:23:09 -0700
From:	Stephen Warren <swarren@...dotorg.org>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Alessandro Zummo <a.zummo@...ertech.it>
Cc:	rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org,
	Stephen Warren <swarren@...dia.com>, <stable@...r.kernel.org>
Subject: [PATCH V2] rtc: max8907: weekday encoding fixes

From: Stephen Warren <swarren@...dia.com>

The current MAX8907 driver has two issues related to weekday value
handling:

1)

The HW WEEKDAY register has range 0..6 rather than 1..7 as documented.
Note that I validated the actual HW range by observing the HW register
roll from 6->0 rather than 6->7->1 as would otherwise be expected.

This matches Linux's tm_wday range of 0..6.

When the CMOS RAM content is lost, the date returned from the device is
2007-01-01 00:00:00, which is a Monday. The WEEKDAY register reads 1 in
this case. This matches the numbering in Linux's tm_wday field.

Hence we should write Linux's tm_wday value to the register without
modifying it. Hence, remove the +1/-1 calculations for WEEKDAY/tm_wday.

2)

There's no need to make alarms match on the WEEKDAY register, since the
other fields together uniquely define the alarm date/time. Ignoring
the WEEKDAY value in the match isolates the driver from any incorrect
value in the current time copy of the WEEKDAY register.

Each change individually, or both together, solves an issue that I
observed; "hwclock -r" would time out waiting for its alarm to fire if
the CMOS RAM content had been lost, and hence the WEEKDAY register value
mismatched what the driver expected it to be. "hwclock -w" would solve
this by over-writing the HW default WEEKDAY register value with what the
driver expected.

Cc: <stable@...r.kernel.org>
Signed-off-by: Stephen Warren <swarren@...dia.com>
---
v2: Re-wrote bullet point (1) in the commit description to be a more
accurate and complete description of the WEEKDAY register values. No
code changes.
---
 drivers/rtc/rtc-max8907.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/rtc/rtc-max8907.c b/drivers/rtc/rtc-max8907.c
index 8e45b3c4aa2f..3032178bd9e6 100644
--- a/drivers/rtc/rtc-max8907.c
+++ b/drivers/rtc/rtc-max8907.c
@@ -51,7 +51,7 @@ static irqreturn_t max8907_irq_handler(int irq, void *data)
 {
 	struct max8907_rtc *rtc = data;

-	regmap_update_bits(rtc->regmap, MAX8907_REG_ALARM0_CNTL, 0x7f, 0);
+	regmap_write(rtc->regmap, MAX8907_REG_ALARM0_CNTL, 0);

 	rtc_update_irq(rtc->rtc_dev, 1, RTC_IRQF | RTC_AF);

@@ -64,7 +64,7 @@ static void regs_to_tm(u8 *regs, struct rtc_time *tm)
 		bcd2bin(regs[RTC_YEAR1]) - 1900;
 	tm->tm_mon = bcd2bin(regs[RTC_MONTH] & 0x1f) - 1;
 	tm->tm_mday = bcd2bin(regs[RTC_DATE] & 0x3f);
-	tm->tm_wday = (regs[RTC_WEEKDAY] & 0x07) - 1;
+	tm->tm_wday = (regs[RTC_WEEKDAY] & 0x07);
 	if (regs[RTC_HOUR] & HOUR_12) {
 		tm->tm_hour = bcd2bin(regs[RTC_HOUR] & 0x01f);
 		if (tm->tm_hour == 12)
@@ -88,7 +88,7 @@ static void tm_to_regs(struct rtc_time *tm, u8 *regs)
 	regs[RTC_YEAR1] = bin2bcd(low);
 	regs[RTC_MONTH] = bin2bcd(tm->tm_mon + 1);
 	regs[RTC_DATE] = bin2bcd(tm->tm_mday);
-	regs[RTC_WEEKDAY] = tm->tm_wday + 1;
+	regs[RTC_WEEKDAY] = tm->tm_wday;
 	regs[RTC_HOUR] = bin2bcd(tm->tm_hour);
 	regs[RTC_MIN] = bin2bcd(tm->tm_min);
 	regs[RTC_SEC] = bin2bcd(tm->tm_sec);
@@ -153,7 +153,7 @@ static int max8907_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 	tm_to_regs(&alrm->time, regs);

 	/* Disable alarm while we update the target time */
-	ret = regmap_update_bits(rtc->regmap, MAX8907_REG_ALARM0_CNTL, 0x7f, 0);
+	ret = regmap_write(rtc->regmap, MAX8907_REG_ALARM0_CNTL, 0);
 	if (ret < 0)
 		return ret;

@@ -163,8 +163,7 @@ static int max8907_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 		return ret;

 	if (alrm->enabled)
-		ret = regmap_update_bits(rtc->regmap, MAX8907_REG_ALARM0_CNTL,
-					 0x7f, 0x7f);
+		ret = regmap_write(rtc->regmap, MAX8907_REG_ALARM0_CNTL, 0x77);

 	return ret;
 }
-- 
1.8.1.5

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