linux-kernel - [PATCH] rtc-pm8xxx: Fix issue in RTC write path

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Date:   Wed, 28 Feb 2018 14:21:18 +0530
From:   Mohit Aggarwal <maggarwa@...eaurora.org>
To:     a.zummo@...ertech.it, alexandre.belloni@...e-electrons.com
Cc:     Mohit Aggarwal <maggarwa@...eaurora.org>,
        rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org
Subject: [PATCH] rtc-pm8xxx: Fix issue in RTC write path

In order to set time in rtc, need to disable
rtc hw before writing into rtc registers.

Also fixes disabling of alarm while setting
rtc time.

Change-Id: Ia2c9c922dd78e2ecb92554d5722c894706d83ac0
Signed-off-by: Mohit Aggarwal <maggarwa@...eaurora.org>
---
 drivers/rtc/rtc-pm8xxx.c | 49 +++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 38 insertions(+), 11 deletions(-)

diff --git a/drivers/rtc/rtc-pm8xxx.c b/drivers/rtc/rtc-pm8xxx.c
index fac8355..5309edc 100644
--- a/drivers/rtc/rtc-pm8xxx.c
+++ b/drivers/rtc/rtc-pm8xxx.c
@@ -74,16 +74,18 @@ struct pm8xxx_rtc {
 /*
  * Steps to write the RTC registers.
  * 1. Disable alarm if enabled.
- * 2. Write 0x00 to LSB.
- * 3. Write Byte[1], Byte[2], Byte[3] then Byte[0].
- * 4. Enable alarm if disabled in step 1.
+ * 2. Disable rtc if enabled.
+ * 3. Write 0x00 to LSB.
+ * 4. Write Byte[1], Byte[2], Byte[3] then Byte[0].
+ * 5. Enable rtc if disabled in step 2.
+ * 6. Enable alarm if disabled in step 1.
  */
 static int pm8xxx_rtc_set_time(struct device *dev, struct rtc_time *tm)
 {
 	int rc, i;
 	unsigned long secs, irq_flags;
-	u8 value[NUM_8_BIT_RTC_REGS], alarm_enabled = 0;
-	unsigned int ctrl_reg;
+	u8 value[NUM_8_BIT_RTC_REGS], alarm_enabled = 0, rtc_disabled = 0;
+	unsigned int ctrl_reg, rtc_ctrl_reg;
 	struct pm8xxx_rtc *rtc_dd = dev_get_drvdata(dev);
 	const struct pm8xxx_rtc_regs *regs = rtc_dd->regs;
 
@@ -92,23 +94,38 @@ static int pm8xxx_rtc_set_time(struct device *dev, struct rtc_time *tm)
 
 	rtc_tm_to_time(tm, &secs);
 
+	dev_dbg(dev, "Seconds value to be written to RTC = %lu\n", secs);
+
 	for (i = 0; i < NUM_8_BIT_RTC_REGS; i++) {
 		value[i] = secs & 0xFF;
 		secs >>= 8;
 	}
 
-	dev_dbg(dev, "Seconds value to be written to RTC = %lu\n", secs);
-
 	spin_lock_irqsave(&rtc_dd->ctrl_reg_lock, irq_flags);
 
-	rc = regmap_read(rtc_dd->regmap, regs->ctrl, &ctrl_reg);
+	rc = regmap_read(rtc_dd->regmap, regs->alarm_ctrl, &ctrl_reg);
 	if (rc)
 		goto rtc_rw_fail;
 
 	if (ctrl_reg & regs->alarm_en) {
 		alarm_enabled = 1;
 		ctrl_reg &= ~regs->alarm_en;
-		rc = regmap_write(rtc_dd->regmap, regs->ctrl, ctrl_reg);
+		rc = regmap_write(rtc_dd->regmap, regs->alarm_ctrl, ctrl_reg);
+		if (rc) {
+			dev_err(dev, "Write to RTC Alarm control register failed\n");
+			goto rtc_rw_fail;
+		}
+	}
+
+	/* Disable RTC H/w before writing on RTC register */
+	rc = regmap_read(rtc_dd->regmap, regs->ctrl, &rtc_ctrl_reg);
+	if (rc)
+		goto rtc_rw_fail;
+
+	if (rtc_ctrl_reg & PM8xxx_RTC_ENABLE) {
+		rtc_disabled = 1;
+		rtc_ctrl_reg &= ~PM8xxx_RTC_ENABLE;
+		rc = regmap_write(rtc_dd->regmap, regs->ctrl, rtc_ctrl_reg);
 		if (rc) {
 			dev_err(dev, "Write to RTC control register failed\n");
 			goto rtc_rw_fail;
@@ -137,11 +154,21 @@ static int pm8xxx_rtc_set_time(struct device *dev, struct rtc_time *tm)
 		goto rtc_rw_fail;
 	}
 
+	/* Enable RTC H/w after writing on RTC register */
+	if (rtc_disabled) {
+		rtc_ctrl_reg |= PM8xxx_RTC_ENABLE;
+		rc = regmap_write(rtc_dd->regmap, regs->ctrl, rtc_ctrl_reg);
+		if (rc) {
+			dev_err(dev, "Write to RTC control register failed\n");
+			goto rtc_rw_fail;
+		}
+	}
+
 	if (alarm_enabled) {
 		ctrl_reg |= regs->alarm_en;
-		rc = regmap_write(rtc_dd->regmap, regs->ctrl, ctrl_reg);
+		rc = regmap_write(rtc_dd->regmap, regs->alarm_ctrl, ctrl_reg);
 		if (rc) {
-			dev_err(dev, "Write to RTC control register failed\n");
+			dev_err(dev, "Write to RTC Alarm control register failed\n");
 			goto rtc_rw_fail;
 		}
 	}
-- 
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