| Message ID | 1429574122-4284-1-git-send-email-nm@ti.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 04/20/2015 06:55 PM, Nishanth Menon wrote: > Alarm interrupt enable register is at offset 0x7, while the time > registers for the alarm follow that. When we program Alarm interrupt > enable prior to programming the time, it is possible that previous > time value could be close or match at the time of alarm enable > resulting in interrupt trigger which is unexpected (and does not match > the time we expect it to trigger). > > To prevent this scenario from occurring, program the ALM0_EN bit only > after the alarm time is appropriately programmed. > > Of course, I2C programming is non-atomic, so there are loopholes where > the interrupt wont trigger if the time requested is in the past at > the time of programming the ALM0_EN bit. However, we will not have > unexpected interrupts while the time is programmed after the interrupt > are enabled. > > Signed-off-by: Nishanth Menon <nm@ti.com> > --- > drivers/rtc/rtc-ds1307.c | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > > diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c > index 4ffabb322a9a..59f9ecf323d5 100644 > --- a/drivers/rtc/rtc-ds1307.c > +++ b/drivers/rtc/rtc-ds1307.c > @@ -742,17 +742,17 @@ static int mcp794xx_set_alarm(struct device *dev, struct rtc_wkalrm *t) > regs[6] &= ~MCP794XX_BIT_ALMX_IF; > /* Set alarm match: second, minute, hour, day, date, month. */ > regs[6] |= MCP794XX_MSK_ALMX_MATCH; > - > - if (t->enabled) > - regs[0] |= MCP794XX_BIT_ALM0_EN; > - else > - regs[0] &= ~MCP794XX_BIT_ALM0_EN; > + /* Disable interrupt. We will not enable until completely programed */ ^^ typo here. s/programed/programmed > + regs[0] &= ~MCP794XX_BIT_ALM0_EN; > > ret = ds1307->write_block_data(client, MCP794XX_REG_CONTROL, 10, regs); > if (ret < 0) > return ret; > > - return 0; > + if (!t->enabled) > + return 0; > + regs[0] |= MCP7941X_BIT_ALM0_EN; ^^ messed up git commit --amend :( > + return i2c_smbus_write_byte_data(client, MCP794XX_REG_CONTROL, regs[0]); > } > > static int mcp794xx_alarm_irq_enable(struct device *dev, unsigned int enabled) > will repost a rev2 - apologies on the noise.
diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c index 4ffabb322a9a..59f9ecf323d5 100644 --- a/drivers/rtc/rtc-ds1307.c +++ b/drivers/rtc/rtc-ds1307.c @@ -742,17 +742,17 @@ static int mcp794xx_set_alarm(struct device *dev, struct rtc_wkalrm *t) regs[6] &= ~MCP794XX_BIT_ALMX_IF; /* Set alarm match: second, minute, hour, day, date, month. */ regs[6] |= MCP794XX_MSK_ALMX_MATCH; - - if (t->enabled) - regs[0] |= MCP794XX_BIT_ALM0_EN; - else - regs[0] &= ~MCP794XX_BIT_ALM0_EN; + /* Disable interrupt. We will not enable until completely programed */ + regs[0] &= ~MCP794XX_BIT_ALM0_EN; ret = ds1307->write_block_data(client, MCP794XX_REG_CONTROL, 10, regs); if (ret < 0) return ret; - return 0; + if (!t->enabled) + return 0; + regs[0] |= MCP7941X_BIT_ALM0_EN; + return i2c_smbus_write_byte_data(client, MCP794XX_REG_CONTROL, regs[0]); } static int mcp794xx_alarm_irq_enable(struct device *dev, unsigned int enabled)
Alarm interrupt enable register is at offset 0x7, while the time registers for the alarm follow that. When we program Alarm interrupt enable prior to programming the time, it is possible that previous time value could be close or match at the time of alarm enable resulting in interrupt trigger which is unexpected (and does not match the time we expect it to trigger). To prevent this scenario from occurring, program the ALM0_EN bit only after the alarm time is appropriately programmed. Of course, I2C programming is non-atomic, so there are loopholes where the interrupt wont trigger if the time requested is in the past at the time of programming the ALM0_EN bit. However, we will not have unexpected interrupts while the time is programmed after the interrupt are enabled. Signed-off-by: Nishanth Menon <nm@ti.com> --- drivers/rtc/rtc-ds1307.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)