linux-kernel - Re: [PATCH v5 6/7] iommu/exynos: Add runtime pm support

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Date:   Mon, 24 Oct 2016 07:19:44 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Sricharan <sricharan@...eaurora.org>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-samsung-soc@...r.kernel.org
Cc:     'Tomeu Vizoso' <tomeu.vizoso@...labora.com>,
        'Bartlomiej Zolnierkiewicz' <b.zolnierkie@...sung.com>,
        'Greg Kroah-Hartman' <gregkh@...uxfoundation.org>,
        'Kevin Hilman' <khilman@...nel.org>,
        "'Rafael J. Wysocki'" <rjw@...ysocki.net>,
        'Tomasz Figa' <tomasz.figa@...il.com>,
        'Krzysztof Kozlowski' <krzk@...nel.org>,
        'Inki Dae' <inki.dae@...sung.com>,
        'Tobias Jakobi' <tjakobi@...h.uni-bielefeld.de>,
        "'Luis R. Rodriguez'" <mcgrof@...nel.org>,
        'Kukjin Kim' <kgene@...nel.org>,
        'Mark Brown' <broonie@...nel.org>,
        'Lukas Wunner' <lukas@...ner.de>
Subject: Re: [PATCH v5 6/7] iommu/exynos: Add runtime pm support

Hi Sricharan


On 2016-10-22 07:50, Sricharan wrote:
>
>> This patch adds runtime pm implementation, which is based on previous
>> suspend/resume code. SYSMMU controller is now being enabled/disabled mainly
> > from the runtime pm callbacks. System sleep callbacks relies on generic
>> pm_runtime_force_suspend/pm_runtime_force_resume helpers. To ensure
>> internal state consistency, additional lock for runtime pm transitions
>> was introduced.
>>
>> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
>> ---
>> drivers/iommu/exynos-iommu.c | 45 +++++++++++++++++++++++++++++++++++---------
>> 1 file changed, 36 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c
>> index a959443e6f33..5e6d7bbf9b70 100644
>> --- a/drivers/iommu/exynos-iommu.c
>> +++ b/drivers/iommu/exynos-iommu.c
>> @@ -206,6 +206,7 @@ struct sysmmu_fault_info {
>> struct exynos_iommu_owner {
>> 	struct list_head controllers;	/* list of sysmmu_drvdata.owner_node */
>> 	struct iommu_domain *domain;	/* domain this device is attached */
>> +	struct mutex rpm_lock;		/* for runtime pm of all sysmmus */
>> };
>>
>> /*
>> @@ -594,40 +595,46 @@ static int __init exynos_sysmmu_probe(struct platform_device *pdev)
>> 	return 0;
>> }
>>
>> -#ifdef CONFIG_PM_SLEEP
>> -static int exynos_sysmmu_suspend(struct device *dev)
>> +static int __maybe_unused exynos_sysmmu_suspend(struct device *dev)
>> {
>> 	struct sysmmu_drvdata *data = dev_get_drvdata(dev);
>> 	struct device *master = data->master;
>>
>> 	if (master) {
>> -		pm_runtime_put(dev);
>> +		struct exynos_iommu_owner *owner = master->archdata.iommu;
>> +
>> +		mutex_lock(&owner->rpm_lock);
> More of a device link question,
> To understand, i see that with device link + runtime, the supplier
> callbacks are not called for irqsafe clients, even if supplier is irqsafe.
> Why so ?

Frankly I didn't care about irqsafe runtime pm, because there is no such 
need
for Exynos platform and its drivers. Exynos power domain driver also doesn't
support irqsafe mode.

>
>> 		if (data->domain) {
>> 			dev_dbg(data->sysmmu, "saving state\n");
>> 			__sysmmu_disable(data);
>> 		}
>> +		mutex_unlock(&owner->rpm_lock);
>> 	}
>> 	return 0;
>> }
>>
>> -static int exynos_sysmmu_resume(struct device *dev)
>> +static int __maybe_unused exynos_sysmmu_resume(struct device *dev)
>> {
>> 	struct sysmmu_drvdata *data = dev_get_drvdata(dev);
>> 	struct device *master = data->master;
>>
>> 	if (master) {
>> -		pm_runtime_get_sync(dev);
>> +		struct exynos_iommu_owner *owner = master->archdata.iommu;
>> +
>> +		mutex_lock(&owner->rpm_lock);
>> 		if (data->domain) {
>> 			dev_dbg(data->sysmmu, "restoring state\n");
>> 			__sysmmu_enable(data);
>> 		}
>> +		mutex_unlock(&owner->rpm_lock);
>> 	}
>> 	return 0;
>> }
>> -#endif
>>
>> static const struct dev_pm_ops sysmmu_pm_ops = {
>> -	SET_LATE_SYSTEM_SLEEP_PM_OPS(exynos_sysmmu_suspend, exynos_sysmmu_resume)
>> +	SET_RUNTIME_PM_OPS(exynos_sysmmu_suspend, exynos_sysmmu_resume, NULL)
>> +	SET_LATE_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
>> +				     pm_runtime_force_resume)
>> };
>   Is this needed to be LATE_SYSTEM_SLEEP_PM_OPS with device links to take care
>    of the order ?

Hmmm. LASE_SYSTEM_SLEEP_PM_OPS is a left over from the previous versions 
of the driver,
which doesn't use device links. You are right, that "normal" 
SYSTEM_SLEEP_PM_OPS should
be enough assuming that device links will take care of the proper call 
sequence between
consumer and supplier device.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland