linux-kernel - Re: [PATCH 02/14] clocksource/drivers/timer-ti-dm: Add clockevent and clocksource support

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Message-ID: <20200427152329.GR37466@atomide.com>
Date:   Mon, 27 Apr 2020 08:23:29 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Keerthy <j-keerthy@...com>,
        Lokesh Vutla <lokeshvutla@...com>,
        Tero Kristo <t-kristo@...com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Nikolaus Schaller" <hns@...delico.com>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        Adam Ford <aford173@...il.com>,
        Andreas Kemnade <andreas@...nade.info>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, devicetree@...r.kernel.org,
        linux-clk@...r.kernel.org, Rob Herring <robh@...nel.org>
Subject: Re: [PATCH 02/14] clocksource/drivers/timer-ti-dm: Add clockevent
 and clocksource support

* Daniel Lezcano <daniel.lezcano@...aro.org> [200427 15:03]:
> On 27/04/2020 16:31, Tony Lindgren wrote:
> > Hi,
> > 
> > * Daniel Lezcano <daniel.lezcano@...aro.org> [200427 09:19]:
> >> On 17/04/2020 18:55, Tony Lindgren wrote:
> >>> --- a/Documentation/devicetree/bindings/timer/ti,timer.txt
> >>> +++ b/Documentation/devicetree/bindings/timer/ti,timer.txt
> >>> @@ -14,6 +14,8 @@ Required properties:
> >>>  			ti,omap5430-timer (applicable to OMAP543x devices)
> >>>  			ti,am335x-timer	(applicable to AM335x devices)
> >>>  			ti,am335x-timer-1ms (applicable to AM335x devices)
> >>> +			ti,dmtimer-clockevent (when used as for clockevent)
> >>> +			ti,dmtimer-clocksource (when used as for clocksource)
> >>
> >> Please, submit a separate patch for this.
> >>
> >> Before you resend as is, this will be nacked as clocksource / clockevent
> >> is not a hardware description but a Linux thing.
> >>
> >> Finding a way to characterize that from the DT is an endless discussion
> >> since years, so I suggest to use a single property for the timer eg
> >> <ti,dmtimer> and initialize the clocksource and the clockevent in the
> >> driver.
> > 
> > Hmm good point. We still need to specify which timer is a clocksource
> > and which one a clockevent somehow.
> > 
> > Maybe we could have a generic properties like the clock framework such as:
> > 
> > assigned-system-clocksource
> > assigned-system-clockevent
> 
> I think that will be the same problem :/

Seems like other SoCs have the same issue too with multiple timers
to configure.

> Is it possible to check the interrupt for the clockevent ? A timer node
> with the interrrupt is the clockevent, without it is a clocksource.

OK let's try that. So the configuration would become then:

compatible = "ti,dmtimer;	/* reserved for system timers */
/delete-property/interrupts;	/* ok so it's a clocksource */
/delete-property/interrupts-extended;

Regards,

Tony