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From: John Stultz <john.stultz@linaro.org>
To: Claudiu Beznea <Claudiu.Beznea@microchip.com>
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Subject: Re: [PATCH 0/7] add support for clocksource/clockevent DT selection
Date: Wed, 11 Sep 2019 09:06:01 -0700
Message-ID: <CALAqxLXRVc-K5q=me1=5tA0XYT7ncrArSoD+hq=JOGWVF9-7SQ@mail.gmail.com> (raw)
In-Reply-To: <cb451591-88ad-f1b3-b654-cea86ae11cac@microchip.com>

On Tue, Sep 10, 2019 at 11:52 PM <Claudiu.Beznea@microchip.com> wrote:
> On 10.09.2019 19:05, John Stultz wrote:
> > External E-Mail
> > On Tue, Sep 10, 2019 at 6:47 AM Claudiu Beznea
> > <claudiu.beznea@microchip.com> wrote:
> >>
> >> This series adds support to permit the selection of clocksource/clockevent
> >> via DT.
> >
> > Sorry about this, but could you try to include more of a rational for
> > *why* this would be useful in your cover-letter/commit messages?
> >
>
> Sorry for not being to clear in the cover letter.
>
> The case I am trying to solve here is as follows:
> The timer hardware for which I publish a driver at [1] cannot work at the
> same time as a clocksource and clockevent. On some of our platforms we have
> more than one such a timer. So we could use one hardware resource as
> clocksource and one as clockevent but not one for both.
> Due to this, I proposed in the driver at [1] to have 1st probed hardware to
> work as clocksource and the 2nd one to work as clockevent.
[snip]
> Due to this Daniel proposed to have an unified mechanism for this scenario,
> see [2], (something like what I proposed in this series), such that to have
> a determinism b/w the function that the hardware resources would behave
> (either clocksource or clockevent or both).

Thanks for the additional explanation! I'd suggest adding something
like it to the commit logs for next time.

Personally, I tend to think of DT bindings as a big harry ABI, and as
such avoid it as much as possible. :)

I'd probably favor driver tweaks to ensure the hardware only gets
registered once for each, using a minimal DT compatible or flag on the
hardware to better describe the underlying hardware quirk that keeps
it from being usable for both clocksource and clockevent usage.

That way the DT sticks to accurately describing hardware, instead of
system/software-abstraction configuration details that just apply for
Linux.

But, again, I'm not really a DT person, so I'll defer to Rob and Daniel.

thanks
-john

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Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-10 13:47 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
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 [this message]
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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