linux-kernel - Re: [PATCH v5 3/8] ARM: dts: rockchip: add timer entries to rk3188 SoC

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Message-ID: <20170130133528.GG2206@mai>
Date:   Mon, 30 Jan 2017 14:35:28 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Alexander Kochetkov <al.kochet@...il.com>
Cc:     Heiko Stuebner <heiko@...ech.de>,
        LKML <linux-kernel@...r.kernel.org>, devicetree@...r.kernel.org,
        LAK <linux-arm-kernel@...ts.infradead.org>,
        linux-rockchip@...ts.infradead.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Caesar Wang <wxt@...k-chips.com>,
        Huang Tao <huangtao@...k-chips.com>
Subject: Re: [PATCH v5 3/8] ARM: dts: rockchip: add timer entries to rk3188
 SoC

On Mon, Jan 30, 2017 at 04:13:07PM +0300, Alexander Kochetkov wrote:
> 
> > 30 янв. 2017 г., в 15:04, Daniel Lezcano <daniel.lezcano@...aro.org> написал(а):
> > 
> > There is no case when the rockchip timer is used for the clockevent.
> The is already timer entry for rk3228 in the DT. And it act as clockevent. I guess it work as backup,
> but I cannot test it also. In order to not break DT compatibility I had to provide one timer to be
> initialized as clockevent. And implemented implicit rule the driver (first DT timer - clockevent,
> second DT timer - clocksource) already exists for other timers.
> 
> > If I'm not wrong, you can check /proc/interrupts and see there is no interrupt
> > on the rockchip timer.
> 
> Yes, you right here. I’ve temporary disable smp_twd to test rockchip timer interrupts.
> There is no interrupt on the rockchip timer during normal work.
> 
> > - when the CPU enters a deep idle state. But such state does not exist on rk3188
> ARM chip/revision specific?

rk3188 specific. Applies also for rk3288 AFAICT. Without entering in the
details, the SoC can't handle that.

> > - when the system goes to suspend. But the timers are stopped in any case and
> >   CPU0 is always on.
> There is timer for rk3228 in the DT. I guess there are situations where it can be used.
> May be the situations are also acceptable for rk3188? May be something like suspend to RAM or
> suspend to HDD? I am not expert in that questions. I can do some tests if you give hint/link.

Nope, rockchip clockevents won't be used, smp_twd will instead.

You can check by commenting the local-timer in the DT, and you should see the
/proc/interrupts line for the rockchip incrementing while the 'twd' are zero.

> So, as I understood you suggest to leave only one timer what can be used as clocksource
> only. I can implement that, but there should be DT rule what allow to setup timer
> as clocksource only. I cannot do more without timer framework support.
> Looks, like I have to wait your patch to implement that.

No, actually I meant the rockchip clockevents won't be used for both rk3188 and
rk3288, they are not needed.

It is for information, this patch is ok.

  -- Daniel

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