linux-kernel - Re: [PATCH v11 19/27] iommu/exynos: add support for power management subsystems.

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Date:	Tue, 18 Mar 2014 16:33:04 +0100
From:	Tomasz Figa <t.figa@...sung.com>
To:	Cho KyongHo <pullip.cho@...sung.com>
Cc:	Linux ARM Kernel <linux-arm-kernel@...ts.infradead.org>,
	Linux DeviceTree <devicetree@...r.kernel.org>,
	Linux IOMMU <iommu@...ts.linux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux Samsung SOC <linux-samsung-soc@...r.kernel.org>,
	Antonios Motakis <a.motakis@...tualopensystems.com>,
	Grant Grundler <grundler@...omium.org>,
	Joerg Roedel <joro@...tes.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Prathyush <prathyush.k@...sung.com>,
	Rahul Sharma <rahul.sharma@...sung.com>,
	Sachin Kamat <sachin.kamat@...aro.org>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Varun Sethi <Varun.Sethi@...escale.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Kevin Hilman <khilman@...aro.org>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v11 19/27] iommu/exynos: add support for power management
 subsystems.

On 18.03.2014 12:23, Cho KyongHo wrote:
> On Fri, 14 Mar 2014 17:07:53 +0100, Tomasz Figa wrote:
>> Hi KyongHo,
>>
>> On 14.03.2014 06:10, Cho KyongHo wrote:

[snip]

>>> @@ -677,11 +679,40 @@ static int __init exynos_sysmmu_probe(struct platform_device *pdev)
>>>    	platform_set_drvdata(pdev, data);
>>>
>>>    	pm_runtime_enable(dev);
>>> +	data->runtime_active = !pm_runtime_enabled(dev);
>>
>> Hmm, this seems to be a bit misleading. The field is named
>> runtime_active, but the assignment makes it true if PM runtime is _not_
>> enabled (i.e. inactive). Is this correct?
>>
>
> I agree that it may lead misunderstood.
> data->runtime_active actually indicates if electric power is asserted
> to the System MMU. pm_runtime_enable() call must enable runtime pm
> for the given device. If runtime pm is not enabled although pm_runtime_enable()
> is called, CONFIG_PM_RUNTIME is not configured.
>
> Actually, it is replacible with
> if (IS_ENABLED(CONFIG_PM_RUNTIME))
>      data->runtime_active = true;

I would keep it as !pm_runtime_enabled(dev), but rename the field to 
something more meaningful, like data->is_powered_on.

Best regards,
Tomasz
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