linux-kernel - Re: [PATCH v3] clk: add more managed APIs

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Message-ID: <CAKdAkRSWCWrweNyDAJ4Xkc4igmRSexjKvEG57eg+3QnPc7mbRQ@mail.gmail.com>
Date:   Tue, 14 Feb 2017 11:55:20 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Stephen Boyd <sboyd@...eaurora.org>
Cc:     Russell King - ARM Linux <linux@...linux.org.uk>,
        Guenter Roeck <linux@...ck-us.net>,
        Michael Turquette <mturquette@...libre.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-clk@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] clk: add more managed APIs

On Tue, Feb 14, 2017 at 11:44 AM, Stephen Boyd <sboyd@...eaurora.org> wrote:
> On 02/06, Dmitry Torokhov wrote:
>> On Mon, Jan 30, 2017 at 04:57:13PM -0800, Dmitry Torokhov wrote:
>> > When converting a driver to managed resources it is desirable to be able to
>> > manage all resources in the same fashion. This change allows managing clock
>> > prepared and enabled state in the same way we manage many other resources.
>> >
>> > This adds the following managed APIs:
>> >
>> > - devm_clk_prepare()/devm_clk_unprepare();
>> > - devm_clk_prepare_enable()/devm_clk_disable_unprepare().
>> >
>> > Reviewed-by: Guenter Roeck <linux@...ck-us.net>
>> > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
>>
>> It would be awesome if we could get it into 4.11...
>
> I'd prefer we didn't do this. Instead, make clk_put() drop any
> prepare or enables that were done via that clk pointer. Mike
> started to do this before[1], but we have some code that assumes
> it can do:
>
>         clk = clk_get(...)
>         clk_prepare_enable(clk)
>         clk_put(clk)
>
> and have the clk stay on. Those would need to be changed.

That means we'd need to audit entire code base ;(

>
> We would also need Russell's approval to update the clk_put()
> documentation to describe this change in behavior.
>
> [1] http://lkml.kernel.org/r/1438974570-20812-1-git-send-email-mturquette@baylibre.com
>

Note that devm* APIs do not preclude from changing clk_put() behavior
down the road and it is extremely easy to go and
s/devm_clk_prepare_enable/clk_prepare_enable/ once cleanup is
automatic.

Having devm now will help make driver code better (because right now
we either need to add wrappers so devm_add_action_or_reset() can be
used, or continue mixing devm* and goto cleanups, which are often
wrong).

Thanks.

-- 
Dmitry