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 <n...@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. -- Regards, Nishanth Menon -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
