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

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Message-Id: <046978C2-808F-4EC3-9429-063BC1A7CE7B@gmail.com>
Date:   Mon, 30 Jan 2017 16:13:07 +0300
From:   Alexander Kochetkov <al.kochet@...il.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
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


> 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?

> - 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.

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.

Alexander.