linux-kernel - Re: [PATCH v2 0/4] clocksource: rockchip/timer: Support rktimer for rk3399

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Message-ID: <575F814C.104@rock-chips.com>
Date:	Tue, 14 Jun 2016 12:00:12 +0800
From:	"Huang, Tao" <huangtao@...k-chips.com>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Caesar Wang <wxt@...k-chips.com>
Cc:	Heiko Stuebner <heiko@...ech.de>, dianders@...omium.org,
	briannorris@...gle.com, smbarber@...gle.com,
	linux-rockchip@...ts.infradead.org,
	Thomas Gleixner <tglx@...utronix.de>, cf@...k-chips.com,
	devicetree@...r.kernel.org, Xing Zheng <zhengxing@...k-chips.com>,
	Jianqun Xu <jay.xu@...k-chips.com>,
	Masahiro Yamada <yamada.masahiro@...ionext.com>,
	Brian Norris <briannorris@...omium.org>,
	linux-kernel@...r.kernel.org, Shawn Lin <shawn.lin@...k-chips.com>,
	Rob Herring <robh+dt@...nel.org>,
	Will Deacon <will.deacon@....com>,
	Mark Rutland <mark.rutland@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 0/4] clocksource: rockchip/timer: Support rktimer for
 rk3399

Hi Daniel:
On 2016年06月13日 21:06, Daniel Lezcano wrote:
> On Tue, Jun 07, 2016 at 12:54:29PM +0800, Caesar Wang wrote:
>> This series patches had been tested on rockchip inside kernel.
>> In order to support the rk3399 SoC timer and turn off interrupts and IPIs to
>> save power in idle.
> 
> For my personnal information, are the arch_timer in the same power domain 
> than the CPU ? IOW, what is the 'always-on' property in the DT ?

Yes. In our SoC design, all arch (generic) timer in the same power
domain of CPU core. So if one CPU core power down, the arch (generic)
timer will lose it's state and stop working.
While rk timer maybe in peri power domain or pmu power domain, so the
timer will still work when CPU power down.

But before RK3399, all SoCs with CPU power domain, do not support auto
power down while cpu idle. So the arch timer can be seem as always on,
i.e. we don't need a broadcast timer at all.

> 
>> Okay, it still works bootup on rk3288/other SoCs, even though many socs 
>> hasn't used
>> the broadcast timer.
> 
> Yes, unfortunately the SoC design on rk3288 and the previous ones do not 
> allow to use a cpuidle driver with cpu/cluster power down, so obviously the 
> broadcast timer is pointless on these boards :)
> 

You are right.

>> History version:
>> v1:
>> https://lkml.org/lkml/2016/5/25/186
>>
>> Easy to test for my borad.
>> localhost / # cat /proc/interrupts
>> CPU0       CPU1       CPU2       CPU3       CPU4       CPU5
>> 1:          0          0          0          0          0          0     GICv3  29 Edge      arch_timer
>> ...
>> 5:          0          0          0          0          0          0     GICv3 113 Level     rk_timer
>> ..
>>
>> localhost / # cat /proc/timer_list | grep event_handler
>> get "event_handler:  hrtimer_interrupt"
>> event_handler:  tick_handle_oneshot_broadcast
>> event_handler:  hrtimer_interrupt
> 
> What are you trying to demonstrate here ? There are no interrupts for both 
> arch_timer and rk_timer.

I don't know. Maybe Caesar do something wrong :(
This is my output:
           CPU0       CPU1       CPU2       CPU3       CPU4       CPU5

...
  2:       2911       1967       1588       1608       1295       1606
   GICv3  30 Edge      arch_timer
  5:        578        637        684        626        161        165
   GICv3 113 Level     rk_timer