linux-kernel - Re: About clk maintainership [Was: Re: [PULL] Add variants of devm_clk_get for prepared and enabled clocks enabled clocks]

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Message-ID: <20210802163824.GK22278@shell.armlinux.org.uk>
Date:   Mon, 2 Aug 2021 17:38:24 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Cc:     alexandre.belloni@...tlin.com,
        Michael Turquette <mturquette@...libre.com>,
        thierry.reding@...il.com, lee.jones@...aro.org,
        linux-clk@...r.kernel.org, linux-rtc@...r.kernel.org,
        Ludovic.Desroches@...rochip.com, o.rempel@...gutronix.de,
        andy.shevchenko@...il.com, aardelean@...iqon.com,
        linux-pwm@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        broonie@...nel.org, Jonathan.Cameron@...wei.com,
        linux-arm-kernel@...ts.infradead.org, a.zummo@...ertech.it,
        Stephen Boyd <sboyd@...nel.org>, linux-kernel@...r.kernel.org,
        linux-spi@...r.kernel.org, wsa@...nel.org, kernel@...gutronix.de,
        akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
        Claudiu.Beznea@...rochip.com
Subject: Re: About clk maintainership [Was: Re: [PULL] Add variants of
 devm_clk_get for prepared and enabled clocks enabled clocks]

On Mon, Aug 02, 2021 at 05:27:55PM +0200, Uwe Kleine-König wrote:
> Hello Russell,
> 
> On Mon, Aug 02, 2021 at 10:48:10AM +0100, Russell King (Oracle) wrote:
> > I think devm_clk_get() should not be part of CCF but should be
> > part of the interface level - it's silly to have devm_clk_get()
> > being CCF but not clk_get(). The same should go for the other
> > devm wrappers around the plain clk_* interfaces.
> 
> What is the practical difference between "Function X is part of CCF" and
> "Function X is part of the clk interface and there is only CCF who
> implements it"?

clkdev is maintained by me as part of the API, and provides clk_get()
functionality for all clk implementations. To then have devm_clk_get(),
which merely provides a wrapper around clk_get() adding the devm
semantics being part of CCF is not sane - devm_clk_get() isn't
specific to CCF or in fact any clk API implementation.

> > There have been several different approaches to wrapping things up,
> > but here's a question: should we make it easier to do the lazy thing
> > (get+enable) or should we make it easier to be power efficient?
> > Shouldn't we be encouraging people to write power efficient drivers?
> 
> Yeah, sounds compelling, but I wonder if that's of practical importance.
> How many driver authors do you expect to lure into making a better
> driver just because devm_clk_get_prepared() doesn't exist? In contrast:
> How many drivers become simpler with devm_clk_get_prepared() and so
> it becomes easier to maintain them and easier to spot bugs?
> In the absence of devm_clk_get_prepared(), is it better that several
> frameworks (or drivers) open code it?

It probably depends on where you stand on power management and power
efficiency issues. Personally, I would like to see more effort put
into drivers to make them more power efficient, and I believe in the
coming years, power efficiency is going to become a big issue.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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