Re: [PATCH v5 17/27] iommu/mediatek: Add pm runtime callback

Yong Wu
2020-12-29T11:06:52Z

On Wed, 2020-12-23 at 17:32 +0900, Tomasz Figa wrote:
> On Wed, Dec 09, 2020 at 04:00:52PM +0800, Yong Wu wrote:
> > This patch adds pm runtime callback.
> >
> > In pm runtime case, all the registers backup/restore and bclk are
> > controlled in the pm_runtime callback, then pm_suspend is not needed in
> > this case.
> >
> > runtime PM is disabled when suspend, thus we call
> > pm_runtime_status_suspended instead of pm_runtime_suspended.
> >
> > And, m4u doesn't have its special pm runtime domain in previous SoC, in
> > this case dev->power.runtime_status is RPM_SUSPENDED defaultly,
>
> This sounds wrong and could lead to hard to debug errors when the driver
> is changed in the future. Would it be possible to make the behavior
> consistent across the SoCs instead, so that runtime PM status is ACTIVE
> when needed, even on SoCs without an IOMMU PM domain?

Appreciate the reviewing so detailly.

I have tested this.
a) always call pm_runtime_enable.
b) always add device_link with smi_common.

Then, the runtime PM status meet expectation.

We don't call pm_runtime_get_sync so often, thus, we don't always touch
dev->power.lock. this is ok for us.

I will use this in the next version.

>
> > thus add
> > a "dev->pm_domain" checking for the SoC that has pm runtime domain.
> >
> > Signed-off-by: Yong Wu <yong.wu@mediatek.com>
> > ---
> > drivers/iommu/mtk_iommu.c | 22 ++++++++++++++++++++--
> > 1 file changed, 20 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> > index 5614015e5b96..6fe3ee2b2bf5 100644
> > --- a/drivers/iommu/mtk_iommu.c
> > +++ b/drivers/iommu/mtk_iommu.c
> > @@ -808,7 +808,7 @@ static int mtk_iommu_remove(struct platform_device *pdev)
> > return 0;
> > }
> >
> > -static int __maybe_unused mtk_iommu_suspend(struct device *dev)
> > +static int __maybe_unused mtk_iommu_runtime_suspend(struct device *dev)
> > {
> > struct mtk_iommu_data *data = dev_get_drvdata(dev);
> > struct mtk_iommu_suspend_reg *reg = &data->reg;
> > @@ -826,7 +826,7 @@ static int __maybe_unused mtk_iommu_suspend(struct device *dev)
> > return 0;
> > }
> >
> > -static int __maybe_unused mtk_iommu_resume(struct device *dev)
> > +static int __maybe_unused mtk_iommu_runtime_resume(struct device *dev)
> > {
> > struct mtk_iommu_data *data = dev_get_drvdata(dev);
> > struct mtk_iommu_suspend_reg *reg = &data->reg;
> > @@ -853,7 +853,25 @@ static int __maybe_unused mtk_iommu_resume(struct device *dev)
> > return 0;
> > }
> >
> > +static int __maybe_unused mtk_iommu_suspend(struct device *dev)
> > +{
> > + /* runtime PM is disabled when suspend in pm_runtime case. */
> > + if (dev->pm_domain && pm_runtime_status_suspended(dev))
> > + return 0;
> > +
> > + return mtk_iommu_runtime_suspend(dev);
> > +}
> > +
> > +static int __maybe_unused mtk_iommu_resume(struct device *dev)
> > +{
> > + if (dev->pm_domain && pm_runtime_status_suspended(dev))
> > + return 0;
> > +
> > + return mtk_iommu_runtime_resume(dev);
> > +}
>
> Wouldn't it be enough to just use pm_runtime_force_suspend() and
> pm_runtime_force_resume() as system sleep ops?

After above solution, this is ok.

Thanks.
>
> > +
> > static const struct dev_pm_ops mtk_iommu_pm_ops = {
> > + SET_RUNTIME_PM_OPS(mtk_iommu_runtime_suspend, mtk_iommu_runtime_resume, NULL)
> > SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(mtk_iommu_suspend, mtk_iommu_resume)
> > };
> >
> > --
> > 2.18.0
> >
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