linux-kernel - Re: [RFC PATCH v4 3/3] PM / clock_ops: add and enable clocks always if !CONFIG_PM

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Date:	Fri, 7 Nov 2014 14:43:41 +0200
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	<ssantosh@...nel.org>, "Rafael J. Wysocki" <rjw@...ysocki.net>,
	<khilman@...aro.org>, <linux-pm@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>, <grant.likely@...retlab.ca>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Caesar Wang <caesar.wang@...k-chips.com>
Subject: Re: [RFC PATCH v4 3/3] PM / clock_ops: add and enable clocks always
 if !CONFIG_PM_RUNTIME

On 11/06/2014 08:09 PM, Dmitry Torokhov wrote:
> On Thu, Nov 06, 2014 at 03:51:02PM +0200, Grygorii Strashko wrote:
>> Device's clocks need to be enabled always at probing time
>> if !CONFIG_PM_RUNTIME - in that way, device will become accesible
>> and, later, its clocks can be disabled/enabled during system
>> suspend/resume by using pm_clk_suspend/pm_clk_resume APIs.
>>
>> But now, the clocks management code doesn't enable clocks when
>> clocks are being registered per-device by using pm_clk_add/_clk().
>> So, update pm_clk_acquire(), which is called from pm_clk_add/_clk(),
>> to enable clock always if !CONFIG_PM_RUNTIME.
>>
>> Also, Platform PM domains drivers will not have to add code like below
>> each time they need to handle the case when !CONFIG_PM_RUNTIME [1 - 3]:
>>
>>         if (!IS_ENABLED(CONFIG_PM_RUNTIME)) {
>>                 ret = pm_clk_resume(dev);
>>                 if (ret) {
>>                         dev_err(dev, "pm_clk_resume failed %d\n", ret);
>>                         goto clk_err;
>>                 };
>>         }
>>
>> [1] https://lkml.org/lkml/2014/10/3/306
>> [2] https://lkml.org/lkml/2014/10/16/305
>> [3] https://lkml.org/lkml/2014/10/20/249
>>
>> CC: Santosh Shilimkar <ssantosh@...nel.org>
>> CC: Kevin Hilman <khilman@...aro.org>
>> CC: Ulf Hansson <ulf.hansson@...aro.org>
>> CC: Geert Uytterhoeven <geert@...ux-m68k.org>
>> CC: Dmitry Torokhov <dmitry.torokhov@...il.com>
>> CC: Philipp Zabel <p.zabel@...gutronix.de>
>> CC: Caesar Wang <caesar.wang@...k-chips.com>
>>
>> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
>> ---
>> Hi,
>>
>> I marked it as RFC, because:
>>    Generic clock manipulation PM callbacks can be used for any device
>>    for which list of clocks need to be maintained - and it doesn't mean
>>    that this framework need to be always connected to GPD/Runtime PM or
>>    used during suspend resume. Also, for DT-use case - it doesn't perform
>>    any actions (except clk_prepare) on clocks by itself and only
>>    by request from framework's consumer.
>>
>>   For example, it can be reused by Power domain/controller drivers like:
>>   - Rockchip RK3288 PM Domain (https://lkml.org/lkml/2014/11/6/30)
>>   - IMX.6 PU power domain (http://www.spinics.net/lists/arm-kernel/msg360709.html)
>>
>>   to maintain list of clocks for GPD itself and these clocks should not
>>   be enabled by default, because they are used to power on/off Power domain
>>   in a specific way:
>>       - enable all clocks assigned to PD
>>       - power on/off PD
>>       - disable all clocks assigned to PD.
>>   After this patch it will be impossible to reuse Generic clock manipulation PM
>>   callbacks in cases described above.
>
> I'd rather keep it separate and concentrate on making pm_clk* code
> working with the power management core. Individual drivers can easily
> keep list of their clocks for whatever additional purpose they need
> without involving pm_clk* API.
>

In general, I'm ok with this patch for Keystone 2 proposes,
just added some notes about introduced limitations. And  all
current users of pm_clk* APIs will not regress with this patch, because
they will go through different code path if !CONFIG_PM_RUNTIME.

Regards,
-grygorii




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