From: Alexandre Belloni <alexandre.belloni@bootlin.com>
To: Neil Armstrong <narmstrong@baylibre.com>
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Subject: Re: [PATCH 4/7] dt-bindings: chosen: Add clocksource and clockevent selection
Date: Wed, 11 Sep 2019 11:14:58 +0200 [thread overview]
Message-ID: <20190911091458.GD21254@piout.net> (raw)
In-Reply-To: <81da473f-54d7-2a00-61ec-9351cdfcaaf3@baylibre.com>
On 11/09/2019 09:34:27+0200, Neil Armstrong wrote:
> Hi,
>
> On 10/09/2019 15:47, Claudiu Beznea wrote:
> > From: Alexandre Belloni <alexandre.belloni@bootlin.com>
> >
> > Some timer drivers may behave either as clocksource or clockevent
> > or both. Until now, in case of platforms with multiple hardware
> > resources of the same type, the drivers were chosing the first
> > registered hardware resource as clocksource/clockevent and the
> > next one as clockevent/clocksource. Other were using different
> > compatibles (one for each functionality, although its about the
> > same hardware). Add DT bindings to be able to choose the
> > functionality of a timer.
> >
> > Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
> > Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
> > ---
> > Documentation/devicetree/bindings/chosen.txt | 20 ++++++++++++++++++++
> > 1 file changed, 20 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/chosen.txt b/Documentation/devicetree/bindings/chosen.txt
> > index 45e79172a646..aad3034cdbdf 100644
> > --- a/Documentation/devicetree/bindings/chosen.txt
> > +++ b/Documentation/devicetree/bindings/chosen.txt
> > @@ -135,3 +135,23 @@ e.g.
> > linux,initrd-end = <0x82800000>;
> > };
> > };
> > +
> > +linux,clocksource and linux,clockevent
> > +--------------------------------------
> > +
> > +Those nodes have a timer property. This property is a phandle to the timer to be
> > +chosen as the clocksource or clockevent. This is only useful when the platform
> > +has multiple identical timers and it is not possible to let linux make the
> > +correct choice.
> > +
> > +/ {
> > + chosen {
> > + linux,clocksource {
> > + timer = <&timer0>;
> > + };
> > +
> > + linux,clockevent {
> > + timer = <&timer1>;
> > + };
> > + };
> > +};
> >
>
> Why not in aliases ?
>
> aliases {
> clocksource0 = &timer0;
> clockevent0 = &timer1;
> };
>
> since we can have multiple of each, we should not limit ourselves to 1 clkevent
> and 1 clksource.
>
> In the aliases case, each driver would expose both capabilities, and the core would select
> what to enable.
>
For extendability, you need nodes for that because at some point, you
may need to also be able to select the timer frequency. You can't do
that with an alias.
--
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv
next prev parent reply other threads:[~2019-09-11 9:15 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-10 13:47 [PATCH 0/7] add support for clocksource/clockevent DT selection Claudiu Beznea
2019-09-10 13:47 ` [PATCH 1/7] clocksource/drivers/c-sky: request timer_of_init only for probing CPU Claudiu Beznea
2019-09-10 13:47 ` [PATCH 2/7] clocksource: change timer registration macros Claudiu Beznea
2019-09-10 14:49 ` Marc Zyngier
2019-09-10 14:57 ` Claudiu.Beznea
2019-09-10 13:47 ` [PATCH 3/7] clocksource/timer_of: use BIT() macro Claudiu Beznea
2019-09-10 13:47 ` [PATCH 4/7] dt-bindings: chosen: Add clocksource and clockevent selection Claudiu Beznea
2019-09-10 14:32 ` Sudeep Holla
2019-09-10 14:51 ` Claudiu.Beznea
2019-09-10 15:08 ` Sudeep Holla
2019-09-10 15:10 ` Alexandre Belloni
2019-09-11 0:03 ` Linus Walleij
2019-09-11 7:18 ` Claudiu.Beznea
2019-09-12 14:18 ` Linus Walleij
2019-09-30 14:32 ` Rob Herring
2019-10-02 13:32 ` Claudiu.Beznea
2019-09-11 7:34 ` Neil Armstrong
2019-09-11 9:14 ` Alexandre Belloni [this message]
2019-09-10 13:47 ` [PATCH 5/7] clocksource/drivers/timer-of: add support support for timer's functionalities Claudiu Beznea
2019-09-10 13:47 ` [PATCH 6/7] drivers/clocksource/timer-of: keep declaration on one line Claudiu Beznea
2019-09-10 13:47 ` [PATCH 7/7] clocksource/drivers/integrator-ap: parse the chosen node Claudiu Beznea
2019-09-10 23:48 ` Linus Walleij
2019-09-11 7:14 ` Claudiu.Beznea
2019-09-10 16:05 ` [PATCH 0/7] add support for clocksource/clockevent DT selection John Stultz
2019-09-11 6:52 ` Claudiu.Beznea
2019-09-11 16:06 ` John Stultz
2019-09-25 17:19 ` Daniel Lezcano
2019-09-26 8:42 ` Claudiu.Beznea
2019-10-02 13:35 ` Claudiu.Beznea
2019-10-03 10:43 ` Claudiu.Beznea
2019-10-13 18:16 ` Daniel Lezcano
2019-10-15 9:23 ` Claudiu.Beznea
2019-10-18 20:24 ` Daniel Lezcano
2019-10-21 8:58 ` Claudiu.Beznea
2019-10-21 14:17 ` Daniel Lezcano
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