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

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Message-ID: <86b18b0d-08e1-4899-86ea-ed22d3d36dee@DB8EHSMHS028.ehs.local>
Date:	Fri, 16 Aug 2013 10:28:38 -0700
From:	Sören Brinkmann <soren.brinkmann@...inx.com>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
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 Mon, Aug 12, 2013 at 07:02:39PM +0200, Daniel Lezcano wrote:
> 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.

Just to check in. Do you want any additional testing done? Or can I
expect Stephens fix to get merged, so Zynq can use the GT?

	Thanks,
	Sören


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