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

[Marek Szyprowski]

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@xxxxxxxxxxx>
> > ---
> > 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