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From: Adam Ward <adam.ward.opensource@diasemi.com>
To: Alessandro Zummo <a.zummo@towertech.it>
Cc: Support Opensource <support.opensource@diasemi.com>,
	<rtc-linux@googlegroups.com>, <linux-kernel@vger.kernel.org>
Subject: [PATCH v1 1/3] rtc: da9052: Add extra reads with timeouts to avoid returning partially updated values
Date: Wed, 4 Mar 2015 16:13:12 +0000	[thread overview]
Message-ID: <be1c62b94141eb3d2ddd1dfd4416320c2b432299.1425490310.git.adam.ward.opensource@diasemi.com> (raw)
In-Reply-To: <cover.1425490310.git.adam.ward.opensource@diasemi.com>

The RTC is in a different clock domain so a quick read after write
can retrieve a mangled value of the old/new values

Signed-off-by: Adam Ward <adam.ward.opensource@diasemi.com>
Tested-by: Adam Ward <adam.ward.opensource@diasemi.com>
---
 drivers/rtc/rtc-da9052.c | 87 ++++++++++++++++++++++++++++++++++++------------
 1 file changed, 66 insertions(+), 21 deletions(-)

diff --git a/drivers/rtc/rtc-da9052.c b/drivers/rtc/rtc-da9052.c
index 613c43b..ead02fa 100644
--- a/drivers/rtc/rtc-da9052.c
+++ b/drivers/rtc/rtc-da9052.c
@@ -16,6 +16,7 @@
 #include <linux/platform_device.h>
 #include <linux/rtc.h>
 #include <linux/err.h>
+#include <linux/delay.h>

 #include <linux/mfd/da9052/da9052.h>
 #include <linux/mfd/da9052/reg.h>
@@ -23,6 +24,8 @@
 #define rtc_err(rtc, fmt, ...) \
 		dev_err(rtc->da9052->dev, "%s: " fmt, __func__, ##__VA_ARGS__)

+#define DA9052_GET_TIME_RETRIES 5
+
 struct da9052_rtc {
 	struct rtc_device *rtc;
 	struct da9052 *da9052;
@@ -58,22 +61,43 @@ static irqreturn_t da9052_rtc_irq(int irq, void *data)
 static int da9052_read_alarm(struct da9052_rtc *rtc, struct rtc_time *rtc_tm)
 {
 	int ret;
-	uint8_t v[5];
+	uint8_t v[2][5];
+	int idx = 1;
+	int timeout = DA9052_GET_TIME_RETRIES;

-	ret = da9052_group_read(rtc->da9052, DA9052_ALARM_MI_REG, 5, v);
-	if (ret != 0) {
+	ret = da9052_group_read(rtc->da9052, DA9052_ALARM_MI_REG, 5, &v[0][0]);
+	if (ret) {
 		rtc_err(rtc, "Failed to group read ALM: %d\n", ret);
 		return ret;
 	}

-	rtc_tm->tm_year = (v[4] & DA9052_RTC_YEAR) + 100;
-	rtc_tm->tm_mon  = (v[3] & DA9052_RTC_MONTH) - 1;
-	rtc_tm->tm_mday = v[2] & DA9052_RTC_DAY;
-	rtc_tm->tm_hour = v[1] & DA9052_RTC_HOUR;
-	rtc_tm->tm_min  = v[0] & DA9052_RTC_MIN;
+	do {
+		ret = da9052_group_read(rtc->da9052,
+					DA9052_ALARM_MI_REG, 5, &v[idx][0]);
+		if (ret) {
+			rtc_err(rtc, "Failed to group read ALM: %d\n", ret);
+			return ret;
+		}

-	ret = rtc_valid_tm(rtc_tm);
-	return ret;
+		if (memcmp(&v[0][0], &v[1][0], 5) == 0) {
+			rtc_tm->tm_year = (v[0][4] & DA9052_RTC_YEAR) + 100;
+			rtc_tm->tm_mon  = (v[0][3] & DA9052_RTC_MONTH) - 1;
+			rtc_tm->tm_mday = v[0][2] & DA9052_RTC_DAY;
+			rtc_tm->tm_hour = v[0][1] & DA9052_RTC_HOUR;
+			rtc_tm->tm_min  = v[0][0] & DA9052_RTC_MIN;
+
+			ret = rtc_valid_tm(rtc_tm);
+			return ret;
+		}
+
+		idx = (1-idx);
+		msleep(20);
+
+	} while (timeout--);
+
+	rtc_err(rtc, "Timed out reading alarm time\n");
+
+	return -EIO;
 }

 static int da9052_set_alarm(struct da9052_rtc *rtc, struct rtc_time *rtc_tm)
@@ -135,24 +159,45 @@ static int da9052_rtc_get_alarm_status(struct da9052_rtc *rtc)
 static int da9052_rtc_read_time(struct device *dev, struct rtc_time *rtc_tm)
 {
 	struct da9052_rtc *rtc = dev_get_drvdata(dev);
-	uint8_t v[6];
 	int ret;
+	uint8_t v[2][6];
+	int idx = 1;
+	int timeout = DA9052_GET_TIME_RETRIES;

-	ret = da9052_group_read(rtc->da9052, DA9052_COUNT_S_REG, 6, v);
-	if (ret < 0) {
+	ret = da9052_group_read(rtc->da9052, DA9052_COUNT_S_REG, 6, &v[0][0]);
+	if (ret) {
 		rtc_err(rtc, "Failed to read RTC time : %d\n", ret);
 		return ret;
 	}

-	rtc_tm->tm_year = (v[5] & DA9052_RTC_YEAR) + 100;
-	rtc_tm->tm_mon  = (v[4] & DA9052_RTC_MONTH) - 1;
-	rtc_tm->tm_mday = v[3] & DA9052_RTC_DAY;
-	rtc_tm->tm_hour = v[2] & DA9052_RTC_HOUR;
-	rtc_tm->tm_min  = v[1] & DA9052_RTC_MIN;
-	rtc_tm->tm_sec  = v[0] & DA9052_RTC_SEC;
+	do {
+		ret = da9052_group_read(rtc->da9052,
+					DA9052_COUNT_S_REG, 6, &v[idx][0]);
+		if (ret) {
+			rtc_err(rtc, "Failed to read RTC time : %d\n", ret);
+			return ret;
+		}

-	ret = rtc_valid_tm(rtc_tm);
-	return ret;
+		if (memcmp(&v[0][0], &v[1][0], 6) == 0) {
+			rtc_tm->tm_year = (v[0][5] & DA9052_RTC_YEAR) + 100;
+			rtc_tm->tm_mon  = (v[0][4] & DA9052_RTC_MONTH) - 1;
+			rtc_tm->tm_mday = v[0][3] & DA9052_RTC_DAY;
+			rtc_tm->tm_hour = v[0][2] & DA9052_RTC_HOUR;
+			rtc_tm->tm_min  = v[0][1] & DA9052_RTC_MIN;
+			rtc_tm->tm_sec  = v[0][0] & DA9052_RTC_SEC;
+
+			ret = rtc_valid_tm(rtc_tm);
+			return ret;
+		}
+
+		idx = (1-idx);
+		msleep(20);
+
+	} while (timeout--);
+
+	rtc_err(rtc, "Timed out reading time\n");
+
+	return -EIO;
 }

 static int da9052_rtc_set_time(struct device *dev, struct rtc_time *tm)
-- 
end-of-patch for rtc: da9052: Corrections to access, validation and capability


  reply	other threads:[~2015-03-04 17:38 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-04 17:31 [PATCH v1 0/3] rtc: da9052: Corrections to access, validation and capability Adam Ward
2015-03-04 16:13 ` Adam Ward [this message]
2015-03-04 16:13 ` [PATCH v1 2/3] rtc: da9052: Add constraints to set valid year Adam Ward
2015-03-04 16:13 ` [PATCH v1 3/3] rtc: da9052: Register ability of alarm to wake device from suspend Adam Ward

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