Re: [PATCH] rtc: ds1307: improve weekday handling
From: Alexandre Belloni <hidden>
Date: 2017-08-28 19:15:20
On 28/08/2017 at 20:37:21 +0200, Heiner Kallweit wrote:
mcp794xx as one chip supported by this driver needs the weekday for alarm matching. RTC core ignores the weekday so we can't rely on the values we receive in member tm_wday of struct rtc_time. Therefore calculate the weekday from date/time when setting the time and setting the alarm time for mcp794xx. When having this in place we don't have to check the weekday at each driver load. After a chip reset date/time and weekday may be out of sync but in this case date/time need to be set anyway.
Nope, the core issue is that you can actually set an alarm in the future without setting the time beforehand so this as to be fixed in the probe (this was the issue as reported at the time of the fix).
quoted hunk ↗ jump to hunk
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com> --- drivers/rtc/rtc-ds1307.c | 39 +++++++++++++++------------------------ 1 file changed, 15 insertions(+), 24 deletions(-)diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c index 9d680d36..83b8c997 100644 --- a/drivers/rtc/rtc-ds1307.c +++ b/drivers/rtc/rtc-ds1307.c@@ -437,6 +437,18 @@ static int ds1307_get_time(struct device *dev, struct rtc_time *t) return rtc_valid_tm(t); } +/* + * Certain chips need the weekday for alarm matching and tm->t_wday + * may be not or not properly populated + */ +static int ds1307_get_weekday(struct rtc_time *tm) +{ + time64_t secs64 = rtc_tm_to_time64(tm); + int days = div_s64(secs64, 24 * 60 * 60); + + return (days + 4) % 7 + 1; +} + static int ds1307_set_time(struct device *dev, struct rtc_time *t) { struct ds1307 *ds1307 = dev_get_drvdata(dev);@@ -465,7 +477,7 @@ static int ds1307_set_time(struct device *dev, struct rtc_time *t) regs[DS1307_REG_SECS] = bin2bcd(t->tm_sec); regs[DS1307_REG_MIN] = bin2bcd(t->tm_min); regs[DS1307_REG_HOUR] = bin2bcd(t->tm_hour); - regs[DS1307_REG_WDAY] = bin2bcd(t->tm_wday + 1); + regs[DS1307_REG_WDAY] = ds1307_get_weekday(t); regs[DS1307_REG_MDAY] = bin2bcd(t->tm_mday); regs[DS1307_REG_MONTH] = bin2bcd(t->tm_mon + 1);@@ -902,7 +914,7 @@ static int mcp794xx_set_alarm(struct device *dev, struct rtc_wkalrm *t) regs[3] = bin2bcd(t->time.tm_sec); regs[4] = bin2bcd(t->time.tm_min); regs[5] = bin2bcd(t->time.tm_hour); - regs[6] = bin2bcd(t->time.tm_wday + 1); + regs[6] = ds1307_get_weekday(&t->time); regs[7] = bin2bcd(t->time.tm_mday); regs[8] = bin2bcd(t->time.tm_mon + 1);@@ -1355,14 +1367,12 @@ static int ds1307_probe(struct i2c_client *client, { struct ds1307 *ds1307; int err = -ENODEV; - int tmp, wday; + int tmp; const struct chip_desc *chip; bool want_irq; bool ds1307_can_wakeup_device = false; unsigned char regs[8]; struct ds1307_platform_data *pdata = dev_get_platdata(&client->dev); - struct rtc_time tm; - unsigned long timestamp; u8 trickle_charger_setup = 0; ds1307 = devm_kzalloc(&client->dev, sizeof(struct ds1307), GFP_KERNEL);@@ -1642,25 +1652,6 @@ static int ds1307_probe(struct i2c_client *client, bin2bcd(tmp)); } - /* - * Some IPs have weekday reset value = 0x1 which might not correct - * hence compute the wday using the current date/month/year values - */ - ds1307_get_time(ds1307->dev, &tm); - wday = tm.tm_wday; - timestamp = rtc_tm_to_time64(&tm); - rtc_time64_to_tm(timestamp, &tm); - - /* - * Check if reset wday is different from the computed wday - * If different then set the wday which we computed using - * timestamp - */ - if (wday != tm.tm_wday) - regmap_update_bits(ds1307->regmap, MCP794XX_REG_WEEKDAY, - MCP794XX_REG_WEEKDAY_WDAY_MASK, - tm.tm_wday + 1); - if (want_irq || ds1307_can_wakeup_device) { device_set_wakeup_capable(ds1307->dev, true); set_bit(HAS_ALARM, &ds1307->flags);-- 2.14.1
-- Alexandre Belloni, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com