[rtc-linux] Re: [PATCH] rtc: ds1307: Fix relying on reset value for weekday
From: Alexandre Belloni <hidden>
Date: 2016-06-01 12:18:15
Also in:
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Hi, On 01/06/2016 at 16:19:07 +0530, Keerthy wrote :
The reset value of weekday is 0x1. This is wrong since the reset values of the day/month/year make up to Jan 1 2001. When computed weekday comes out to be Monday. On a scale of 1-7(Sunday - Saturday) it should be 0x2. So we should not be relying on the reset value.
Hum, what are the chances that the reset value is actually the correct date/time? Won't that be corrected after the first call to set_time? Until then, the date is not correct so, do we care anyway? Maybe I'm missing something here.
quoted hunk ↗ jump to hunk
Hence compute the wday using the current date/month/year values. Check if reset wday is any different from the computed wday, If different then set the wday which we computed using date/month/year values. Document Referred: http://ww1.microchip.com/downloads/en/DeviceDoc/20002266F.pdf Fixes: 1d1945d261a2af "drivers/rtc/rtc-ds1307.c: add alarm support for mcp7941x chips" Signed-off-by: Keerthy <j-keerthy@ti.com> --- drivers/rtc/rtc-ds1307.c | 28 +++++++++++++++++++++++++++- 1 file changed, 27 insertions(+), 1 deletion(-)diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c index 821d9c0..d9045cc 100644 --- a/drivers/rtc/rtc-ds1307.c +++ b/drivers/rtc/rtc-ds1307.c@@ -602,6 +602,8 @@ static const struct rtc_class_ops ds13xx_rtc_ops = { * Alarm support for mcp794xx devices. */ +#define MCP794XX_REG_WEEKDAY 0x3 +#define MCP794XX_REG_WEEKDAY_WDAY_MASK 0x7 #define MCP794XX_REG_CONTROL 0x07 # define MCP794XX_BIT_ALM0_EN 0x10 # define MCP794XX_BIT_ALM1_EN 0x20@@ -1231,13 +1233,16 @@ static int ds1307_probe(struct i2c_client *client, { struct ds1307 *ds1307; int err = -ENODEV; - int tmp; + int tmp, wday; struct chip_desc *chip = &chips[id->driver_data]; struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent); bool want_irq = false; bool ds1307_can_wakeup_device = false; unsigned char *buf; struct ds1307_platform_data *pdata = dev_get_platdata(&client->dev); + struct rtc_time tm; + unsigned long timestamp; + irq_handler_t irq_handler = ds1307_irq; static const int bbsqi_bitpos[] = {@@ -1526,6 +1531,27 @@ read_rtc: 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(&client->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) { + wday = i2c_smbus_read_byte_data(client, MCP794XX_REG_WEEKDAY); + wday = wday & ~MCP794XX_REG_WEEKDAY_WDAY_MASK; + wday = wday | (tm.tm_wday + 1); + i2c_smbus_write_byte_data(client, MCP794XX_REG_WEEKDAY, wday); + } + if (want_irq) { device_set_wakeup_capable(&client->dev, true); set_bit(HAS_ALARM, &ds1307->flags);-- 1.9.1
-- Alexandre Belloni, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com -- You received this message because you are subscribed to "rtc-linux". Membership options at http://groups.google.com/group/rtc-linux . Please read http://groups.google.com/group/rtc-linux/web/checklist before submitting a driver. --- You received this message because you are subscribed to the Google Groups "rtc-linux" group. To unsubscribe from this group and stop receiving emails from it, send an email to rtc-linux+unsubscribe@googlegroups.com. For more options, visit https://groups.google.com/d/optout.