Merge branch 'for-linus-v3.20' of git://git.infradead.org/linux-ubifs

[cascardo/linux.git] / drivers / rtc / rtc-rk808.c

diff --git a/drivers/rtc/rtc-rk808.c b/drivers/rtc/rtc-rk808.c
index df42257..91ca0bc 100644 (file)
--- a/drivers/rtc/rtc-rk808.c
+++ b/drivers/rtc/rtc-rk808.c
@@ -67,15 +67,21 @@ static int rk808_rtc_readtime(struct device *dev, struct rtc_time *tm)
        /* Force an update of the shadowed registers right now */
        ret = regmap_update_bits(rk808->regmap, RK808_RTC_CTRL_REG,
                                 BIT_RTC_CTRL_REG_RTC_GET_TIME,
-                                0);
+                                BIT_RTC_CTRL_REG_RTC_GET_TIME);
        if (ret) {
                dev_err(dev, "Failed to update bits rtc_ctrl: %d\n", ret);
                return ret;
        }
 
+       /*
+        * After we set the GET_TIME bit, the rtc time can't be read
+        * immediately. So we should wait up to 31.25 us, about one cycle of
+        * 32khz. If we clear the GET_TIME bit here, the time of i2c transfer
+        * certainly more than 31.25us: 16 * 2.5us at 400kHz bus frequency.
+        */
        ret = regmap_update_bits(rk808->regmap, RK808_RTC_CTRL_REG,
                                 BIT_RTC_CTRL_REG_RTC_GET_TIME,
-                                BIT_RTC_CTRL_REG_RTC_GET_TIME);
+                                0);
        if (ret) {
                dev_err(dev, "Failed to update bits rtc_ctrl: %d\n", ret);
                return ret;