Re: Enable arm_global_timer for Zynq brakes boot

["Sören Brinkmann" <soren.brinkmann@xilinx.com>]

Forget this. It's trash. I had to migrate some stuff around due to some
quota issues and missed to update a few scripts. Sorry, I'll rerun this
test.

	Sören

On Tue, Jul 30, 2013 at 03:14:43PM -0700, Sören Brinkmann wrote:
> On Tue, Jul 30, 2013 at 10:47:15AM +0200, Daniel Lezcano wrote:
> > On 07/30/2013 02:03 AM, Sören Brinkmann wrote:
> > > Hi Daniel,
> > > 
> > > On Mon, Jul 29, 2013 at 02:51:49PM +0200, Daniel Lezcano wrote:
> > > (snip)
> > >>
> > >> the CPUIDLE_FLAG_TIMER_STOP flag tells the cpuidle framework the local
> > >> timer will be stopped when entering to the idle state. In this case, the
> > >> cpuidle framework will call clockevents_notify(ENTER) and switches to a
> > >> broadcast timer and will call clockevents_notify(EXIT) when exiting the
> > >> idle state, switching the local timer back in use.
> > > 
> > > I've been thinking about this, trying to understand how this makes my
> > > boot attempts on Zynq hang. IIUC, the wrongly provided TIMER_STOP flag
> > > would make the timer core switch to a broadcast device even though it
> > > wouldn't be necessary. But shouldn't it still work? It sounds like we do
> > > something useless, but nothing wrong in a sense that it should result in
> > > breakage. I guess I'm missing something obvious. This timer system will
> > > always remain a mystery to me.
> > > 
> > > Actually this more or less leads to the question: What is this
> > > 'broadcast timer'. I guess that is some clockevent device which is
> > > common to all cores? (that would be the cadence_ttc for Zynq). Is the
> > > hang pointing to some issue with that driver?
> > 
> > If you look at the /proc/timer_list, which timer is used for broadcasting ?
> 
> In case of a vanilla kernel and with my patches for enabling the global
> timer (I removed the wrongly set flag from the C2 state + adding the DT
> fragment to use the GT), this is what I see (full output from timer_list
> attached):
> 	Tick Device: mode:     1
> 	Broadcast device
> 	Clock Event Device: xttcps_clockevent
> 
> And the local timer seems to be the arm twd timer (also in both cases).
> 
> I don't think I can gather this information for the actual broken case,
> but AFAIK, there shouldn't be any other timer be capable of this for
> Zynq.
> 
> 	Sören
> 

> Timer List Version: v0.7
> HRTIMER_MAX_CLOCK_BASES: 3
> now at 76779317814 nsecs
> 
> cpu: 0
>  clock 0:
>   .base:       c14a0c90
>   .index:      0
>   .resolution: 1 nsecs
>   .get_time:   ktime_get
>   .offset:     0 nsecs
> active timers:
>  #0: <c14a2b50>, menu_hrtimer_notify, S:01, hrtimer_start, swapper/0/0
>  # expires at 76779328789-76779328789 nsecs [in 10975 to 10975 nsecs]
>  #1: <c14a0dd8>, tick_sched_timer, S:01, hrtimer_start, swapper/0/0
>  # expires at 76800000000-76800000000 nsecs [in 20682186 to 20682186 nsecs]
>  #2: <ed956e40>, timerfd_tmrproc, S:01, hrtimer_start, systemd/1
>  # expires at 93249172026-93249172026 nsecs [in 16469854212 to 16469854212 nsecs]
>  #3: <ed956c00>, timerfd_tmrproc, S:01, hrtimer_start, systemd/1
>  # expires at 900000055806-900000055806 nsecs [in 823220737992 to 823220737992 nsecs]
>  clock 1:
>   .base:       c14a0cc8
>   .index:      1
>   .resolution: 1 nsecs
>   .get_time:   ktime_get_real
>   .offset:     975789465870609368 nsecs
> active timers:
>  clock 2:
>   .base:       c14a0d00
>   .index:      2
>   .resolution: 1 nsecs
>   .get_time:   ktime_get_boottime
>   .offset:     0 nsecs
> active timers:
>   .expires_next   : 76779492678 nsecs
>   .hres_active    : 1
>   .nr_events      : 2449
>   .nr_retries     : 66
>   .nr_hangs       : 0
>   .max_hang_time  : 0 nsecs
>   .nohz_mode      : 2
>   .last_tick      : 76780000000 nsecs
>   .tick_stopped   : 1
>   .idle_jiffies   : 4294944973
>   .idle_calls     : 3114
>   .idle_sleeps    : 981
>   .idle_entrytime : 76779354678 nsecs
>   .idle_waketime  : 76779336246 nsecs
>   .idle_exittime  : 76769862116 nsecs
>   .idle_sleeptime : 70735903990 nsecs
>   .iowait_sleeptime: 18432 nsecs
>   .last_jiffies   : 4294944973
>   .next_jiffies   : 4294944976
>   .idle_expires   : 76800000000 nsecs
> jiffies: 4294944973
> 
> cpu: 1
>  clock 0:
>   .base:       c14a9c90
>   .index:      0
>   .resolution: 1 nsecs
>   .get_time:   ktime_get
>   .offset:     0 nsecs
> active timers:
>  #0: <c14a9dd8>, tick_sched_timer, S:01, hrtimer_start_range_ns, swapper/1/0
>  # expires at 76780000000-76780000000 nsecs [in 682186 to 682186 nsecs]
>  clock 1:
>   .base:       c14a9cc8
>   .index:      1
>   .resolution: 1 nsecs
>   .get_time:   ktime_get_real
>   .offset:     975789465870609368 nsecs
> active timers:
>  clock 2:
>   .base:       c14a9d00
>   .index:      2
>   .resolution: 1 nsecs
>   .get_time:   ktime_get_boottime
>   .offset:     0 nsecs
> active timers:
>   .expires_next   : 76780000000 nsecs
>   .hres_active    : 1
>   .nr_events      : 2257
>   .nr_retries     : 61
>   .nr_hangs       : 0
>   .max_hang_time  : 0 nsecs
>   .nohz_mode      : 2
>   .last_tick      : 76700000000 nsecs
>   .tick_stopped   : 0
>   .idle_jiffies   : 4294944965
>   .idle_calls     : 2998
>   .idle_sleeps    : 444
>   .idle_entrytime : 76771944950 nsecs
>   .idle_waketime  : 76768498136 nsecs
>   .idle_exittime  : 76768498136 nsecs
>   .idle_sleeptime : 72124544054 nsecs
>   .iowait_sleeptime: 4276262 nsecs
>   .last_jiffies   : 4294944973
>   .next_jiffies   : 4294944974
>   .idle_expires   : 78880000000 nsecs
> jiffies: 4294944973
> 
> 
> Tick Device: mode:     1
> Broadcast device
> Clock Event Device: xttcps_clockevent
>  max_delta_ns:   1207932479
>  min_delta_ns:   18432
>  mult:           233015
>  shift:          32
>  mode:           1
>  next_event:     9223372036854775807 nsecs
>  set_next_event: xttcps_set_next_event
>  set_mode:       xttcps_set_mode
>  event_handler:  tick_handle_oneshot_broadcast
>  retries:        0
> tick_broadcast_mask: 00000000
> tick_broadcast_oneshot_mask: 00000000
> 
> 
> Tick Device: mode:     1
> Per CPU device: 0
> Clock Event Device: local_timer
>  max_delta_ns:   12884902005
>  min_delta_ns:   1000
>  mult:           715827876
>  shift:          31
>  mode:           3
>  next_event:     76800000000 nsecs
>  set_next_event: twd_set_next_event
>  set_mode:       twd_set_mode
>  event_handler:  hrtimer_interrupt
>  retries:        0
> 
> Tick Device: mode:     1
> Per CPU device: 1
> Clock Event Device: local_timer
>  max_delta_ns:   12884902005
>  min_delta_ns:   1000
>  mult:           715827876
>  shift:          31
>  mode:           3
>  next_event:     76780000000 nsecs
>  set_next_event: twd_set_next_event
>  set_mode:       twd_set_mode
>  event_handler:  hrtimer_interrupt
>  retries:        0
>