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Date: Wed, 4 Mar 2015 16:13:12 +0000
From: Adam Ward <adam.ward.opensource@...semi.com>
To: Alessandro Zummo <a.zummo@...ertech.it>
CC: Support Opensource <support.opensource@...semi.com>,
<rtc-linux@...glegroups.com>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v1 1/3] rtc: da9052: Add extra reads with timeouts to avoid
returning partially updated values
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@...semi.com>
Tested-by: Adam Ward <adam.ward.opensource@...semi.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
--
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