linux-kernel - Re: [PATCH v2] clk: add more managed APIs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAKdAkRT7iPdw877GxZCxa5h+mnczgksmLnpuuF+MuLPwP6zBkw@mail.gmail.com>
Date:   Tue, 31 Jan 2017 10:26:29 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Stephen Boyd <sboyd@...eaurora.org>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        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 v2] clk: add more managed APIs

On Tue, Jan 31, 2017 at 9:20 AM, Guenter Roeck <linux@...ck-us.net> wrote:
> On Mon, Jan 30, 2017 at 04:59:57PM -0800, Dmitry Torokhov wrote:
>> On Mon, Jan 30, 2017 at 11:22:14AM -0800, Guenter Roeck wrote:
>> > On Mon, Jan 30, 2017 at 10:55:51AM -0800, Stephen Boyd wrote:
>> > > On 01/29, 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
>> > > > clocks in the same way we manage many other resources.
>> > >
>> > > Can you please add 'managing clock prepared and enabled state in
>> > > the same way'?
>> > >
>> > > The current wording makes it sound like we don't have
>> > > devm_clk_get() when we do.
>> > >
>> > > >
>> > > > This adds the following managed APIs:
>> > > >
>> > > > - devm_clk_prepare()/devm_clk_unprepare();
>> > > > - devm_clk_prepare_enable()/devm_clk_disable_unprepare().
>> > >
>> > > Wouldn't this be preceded by a devm_clk_get() call? Wouldn't it
>> > > be even shorter to have the APIs
>> > >
>> > >   devm_clk_get_and_prepare()/devm_clk_unprepare_and_put()
>> > >   devm_clk_get_and_prepare_enable()/devm_clk_disable_unprepare_and_put()
>> > >
>> > > instead?
>> > >
>> > In many cases I see
>> >
>> >     devm_clk_get(clk1);
>> >     devm_clk_get(clk2);
>> >     clk_prepare_enable(clk1);
>> >     clk_prepare_enable(clk2);
>> >
>> > Sometimes the calls are intertwined with setting the clock rates.
>> >
>> >     devm_clk_get(clk);
>> >     clk_set_rate(clk, rate);
>> >     clk_prepare_enable(clk);
>> >
>> > Maybe the additional calls make sense; I can imagine they would.
>> > However, I personally would be a bit wary of changing the initialization
>> > order of multi-clock initializations, and I am not sure how a single call
>> > could address setting the rate ([devm_]clk_get_setrate_prepare_enable()
>> > seems like a bit too much).
>> >
>> > [ On a side note, why is there no clk_get_prepare_enable() and
>> >   clk_get_prepare() ? Maybe it would be better to introduce those
>> >   together with the matching devm_ functions in a separate patch
>> >   if they are useful. ]
>> >
>> > > Is there any other subsystem that has similar functionality?
>> > > Regulators? GPIOs? Resets? I'm just curious if those subsystems
>> > > also need similar changes.
>> > >
>> > Ultimately yes, and most already do. If I recall correctly, I tried to
>> > introduce devm_ functions for regulators some time ago, but that was
>> > rejected with the comment that it would invite misuse.  At the time
>> > I accepted that; today my reaction would be to counter that pretty much
>> > everything can be misused, and that the potential for misuse should not
>> > penaltize all the valid use cases.
>>
>> I think we should ping Mark again. The only thing we are achieving is
>> that everyone is using devm_add_action_or_reset() with wrappers around
>> regulator_put().
>>
> regulator_get() has an equivalent devm_regulator_get(). Maybe it was since
> added, or I was thinking about a different function.

I think we also need devm_regulator_enable().

Thanks.

-- 
Dmitry