[PATCH V2] ARM: OMAP: counter: add locking to read_persistent_clock

[R, Sricharan]

Hi Tony,

[snip..]

>> > index dbf1e03..2bc51fb 100644
>> > --- a/arch/arm/plat-omap/counter_32k.c
>> > +++ b/arch/arm/plat-omap/counter_32k.c
>> > @@ -55,22 +55,29 @@ static u32 notrace omap_32k_read_sched_clock(void)
>> >   * nsecs and adds to a monotonically increasing timespec.
>> >   */
>> >  static struct timespec persistent_ts;
>> > -static cycles_t cycles, last_cycles;
>> > +static cycles_t cycles;
>> >  static unsigned int persistent_mult, persistent_shift;
>> > +static DEFINE_SPINLOCK(read_persistent_clock_lock);
>> > +
>> >  static void omap_read_persistent_clock(struct timespec *ts)
>> >  {
>> >     unsigned long long nsecs;
>> > -   cycles_t delta;
>> > -   struct timespec *tsp = &persistent_ts;
>> > +   cycles_t last_cycles;
>> > +   unsigned long flags;
>> > +
>> > +   spin_lock_irqsave(&read_persistent_clock_lock, flags);
>> >
>> >     last_cycles = cycles;
>> >     cycles = sync32k_cnt_reg ? __raw_readl(sync32k_cnt_reg) : 0;
>> > -   delta = cycles - last_cycles;
>> >
>> > -   nsecs = clocksource_cyc2ns(delta, persistent_mult, persistent_shift);
>> > +   nsecs = clocksource_cyc2ns(cycles - last_cycles,
>> > +                                   persistent_mult, persistent_shift);
>
> ..I think there's another bug here where cycles - last_cycles
> returns wrong value when the timer wraps around as cycles_t is
> 64 bits and the counter is 32 bits. It seems it's been there
> since when the read_persistent_clock was added with commit
> d92cfcbe (OMAP: timekeeping: time should not stop during suspend)?
>
> It seems that after this patch cycles should not be cycles_t
> but u32, and the result of cycles - last_cycles should also
> be u32.
>
 cycles_t is defined as  typedef unsigned long cycles_t;
 Am i missing something here ?

Thanks,
 Sricharan