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SubjectRe: [PATCH V2] drivers/rtc/rtc-ds1307.c: Enable the mcp794xx alarm after programming time
On 21/04/2015 at 20:59:15 -0500, Nishanth Menon wrote :
> >> Why is that so? when set alarm is requested for time X, you want
> >> interrupt at time X, not an interrupt for previous configured RTC
> >> alarm time!
> >>
> >
> > You expect at least an interrupt.
> And you will get an interrupt if the event occurs before the i2c burst
> starts. Once the i2cburst does start, you are committing to the new time.

You mean that even if ALM0EN is set after ALM0IF was set to 1, it will
trigger the interrupt? I had a look at the MFP output block diagram
would let me think that this is the case. I was thinking otherwise
before. If that is so, then indeed, your patch is OK.

My concern was about the time between ds1307->write_block_data() and
i2c_smbus_write_byte_data() which actually calls cond_sched().

I fully agree that your patch doesn't change the behaviour for the other
cases you presented and further clean up is to be done in a separate set
of patches.

Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering

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