From 19c999f4ea4ecfb81d923f0feedbf739174900c7 Mon Sep 17 00:00:00 2001 From: Phil Elwell Date: Mon, 29 Oct 2018 14:45:45 +0000 Subject: [PATCH] rtc: pcf8523: Fix oscillator stop bit handling See: https://github.com/raspberrypi/firmware/issues/1065 Signed-off-by: Phil Elwell --- drivers/rtc/rtc-pcf8523.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/drivers/rtc/rtc-pcf8523.c b/drivers/rtc/rtc-pcf8523.c index d1efde3..6f95c7c 100644 --- a/drivers/rtc/rtc-pcf8523.c +++ b/drivers/rtc/rtc-pcf8523.c @@ -100,6 +100,7 @@ static int pcf8523_rtc_read_time(struct device *dev, struct rtc_time *tm) { struct pcf8523 *pcf8523 = dev_get_drvdata(dev); u8 regs[10]; + u32 value; int err; err = regmap_bulk_read(pcf8523->regmap, PCF8523_REG_CONTROL1, regs, @@ -110,6 +111,33 @@ static int pcf8523_rtc_read_time(struct device *dev, struct rtc_time *tm) if ((regs[0] & PCF8523_CONTROL1_STOP) || (regs[3] & PCF8523_SECONDS_OS)) return -EINVAL; + if (regs[0] & PCF8523_SECONDS_OS) { + /* + * If the oscillator was stopped, try to clear the flag. Upon + * power-up the flag is always set, but if we cannot clear it + * the oscillator isn't running properly for some reason. The + * sensible thing therefore is to return an error, signalling + * that the clock cannot be assumed to be correct. + */ + + regs[0] &= ~PCF8523_SECONDS_OS; + + err = regmap_write(pcf8523->regmap, PCF8523_REG_SECONDS, + regs[0]); + if (err < 0) + return err; + + err = regmap_read(pcf8523->regmap, PCF8523_REG_SECONDS, + &value); + if (err < 0) + return err; + + if (value & PCF8523_SECONDS_OS) + return -EAGAIN; + + regs[0] = value; + } + tm->tm_sec = bcd2bin(regs[3] & 0x7f); tm->tm_min = bcd2bin(regs[4] & 0x7f); tm->tm_hour = bcd2bin(regs[5] & 0x3f); -- 2.7.4