linux-kernel - Re: [alsa-devel] [PATCH v6 1/3] clk: x86: Add Atom PMC platform clocks

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Message-ID: <07206bf1-2fab-0bbe-6e1b-762e55f62363@linux.intel.com>
Date:   Fri, 16 Dec 2016 08:57:16 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Stephen Boyd <sboyd@...eaurora.org>,
        ALSA Development Mailing List <alsa-devel@...a-project.org>,
        Irina Tirdea <irina.tirdea@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Michael Turquette <mturquette@...libre.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Takashi Iwai <tiwai@...e.com>,
        platform-driver-x86@...r.kernel.org,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Brown <broonie@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Darren Hart <dvhart@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Len Brown <lenb@...nel.org>, linux-clk@...r.kernel.org,
        Pierre-Louis Bossart <pierre-louis.bossart@...el.com>
Subject: Re: [alsa-devel] [PATCH v6 1/3] clk: x86: Add Atom PMC platform
 clocks

On 12/16/16 2:46 AM, Andy Shevchenko wrote:
> On Fri, Dec 16, 2016 at 7:15 AM, Pierre-Louis Bossart
> <pierre-louis.bossart@...ux.intel.com> wrote:
>> Hi Stephen,
>>
>> can you elaborate on the last comment?
>
> Please don't do top posting.
>
>>>> devm_kasprintf()
>>>
>>> Please no.
>
> That's why I used modal verb "might" instead of "would".
>
>>> It's all local to this function, devm isn't helping anything.
>>> Having one kfree() would be good though. And using init.name for
>>> the clkdev lookup is probably wrong and should be replaced with
>>> something more generic along with an associated device name.
>>
>> I am not sure I understand this last comment.
>> init.name is not a constant, it's made of the "pmc_plt_clk_" string
>> concatenated with an id which directly maps to which hardware clock is
>> registered. Clients use devm_clk_get() with a "pmc_plt_clk_<n>" argument.
>
> Giving more thoughts about design and use of this I would propose to
> do the following.
>
> 1. Create under clock framework something like clk-pmc-atom clock
> driver (see, for example, clk-fractional-divider, though this one
> should indeed go under x86 folder).

apart from the name the current code already does this with code in 
drivers/clk/x86

> 2. In real provider, i.e. pmc_atom, create the necessary clock tree
> with *names*.
>
> Scheme with ID is fragile, imagine another version of PMC where
> ordering would be mixed up? It's not hypothetical since we used to
> have this already in pmc_atom for some registers and bits.

I don't want to deal with hypothetical stuff happening to legacy 
hardware. If there is a problem at some point, it's no big deal to add a 
platform-dependent lookup table and change the registers being accessed.