linux-kernel - Re: Enable arm_global_timer for Zynq brakes boot

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Message-ID: <5209152F.5020307@linaro.org>
Date:	Mon, 12 Aug 2013 19:02:39 +0200
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Sören Brinkmann <soren.brinkmann@...inx.com>
CC:	Stephen Boyd <sboyd@...eaurora.org>, srinivas.kandagatla@...com,
	Russell King <linux@....linux.org.uk>,
	Michal Simek <michal.simek@...inx.com>,
	linux-kernel@...r.kernel.org, Stuart Menefy <stuart.menefy@...com>,
	John Stultz <john.stultz@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: Enable arm_global_timer for Zynq brakes boot

On 08/12/2013 06:53 PM, Sören Brinkmann wrote:
> On Mon, Aug 12, 2013 at 06:49:17PM +0200, Daniel Lezcano wrote:
>> On 08/12/2013 06:32 PM, Sören Brinkmann wrote:
>>> On Mon, Aug 12, 2013 at 09:20:19AM -0700, Stephen Boyd wrote:
>>>> On 08/12/13 09:03, Sören Brinkmann wrote:
>>>>> On Fri, Aug 09, 2013 at 10:27:57AM -0700, Stephen Boyd wrote:
>>>>>> On 08/09, Daniel Lezcano wrote:
>>>>>>> yes, but at least the broadcast mechanism should send an IPI to cpu0 to
>>>>>>> wake it up, no ? As Stephen stated this kind of configuration should has
>>>>>>> never been tested before so the tick broadcast code is not handling this
>>>>>>> case properly IMHO.
>>>>>>>
>>>>>> If you have a per-cpu tick device that isn't suffering from
>>>>>> FEAT_C3_STOP why wouldn't you use that for the tick versus a
>>>>>> per-cpu tick device that has FEAT_C3_STOP? It sounds like there
>>>>>> is a bug in the preference logic or you should boost the rating
>>>>>> of the arm global timer above the twd. Does this patch help? It
>>>>>> should make the arm global timer the tick device and whatever the
>>>>>> cadence timer you have into the broadcast device.
>>>>> I finally got to test your patch. Unfortunately, it makes the system
>>>>> hang even earlier:
>>>>
>>>> Sorry it had a bug depending on the registration order. Can you try this
>>>> one (tabs are probably spaces, sorry)? I will go read through this
>>>> thread to see if we already covered the registration order.
>>>
>>> That did it! Booted straight into the system. 
>>
>> Good news :)
>>
>>> The broadcast device is
>>> the TTC instead of GT, now.
>>>
>>> 	Tick Device: mode:     1
>>> 	Broadcast device
>>> 	Clock Event Device: ttc_clockevent
>>> 	 max_delta_ns:   1207932479
>>> 	 min_delta_ns:   18432
>>> 	 mult:           233015
>>> 	 shift:          32
>>> 	 mode:           1
>>> 	 next_event:     9223372036854775807 nsecs
>>> 	 set_next_event: ttc_set_next_event
>>> 	 set_mode:       ttc_set_mode
>>> 	 event_handler:  tick_handle_oneshot_broadcast
>>> 	 retries:        0
>>> 	
>>> 	tick_broadcast_mask: 00000000
>>> 	tick_broadcast_oneshot_mask: 00000000
>>
>> At the first glance, the timer broadcast usage is not set, right ? Can
>> you try with the cpuidle flag even if it is not needed ?
> 
> It's actually present. I have a clean 3.11-rc3 and the only changes are
> my patch to enable the GT and Stephen's fix.
> The cpuidle stats show both idle states being used.

Ah, right. The tick_broadcast_mask is not set because the arm global
timer has not the CLOCK_EVT_FEAT_C3STOP feature flag set.

Thanks
  -- Daniel


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