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

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Date:   Tue, 29 Dec 2020 19:06:00 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     Tomasz Figa <tfiga@...omium.org>
CC:     Joerg Roedel <joro@...tes.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>, <youlin.pei@...iatek.com>,
        <devicetree@...r.kernel.org>,
        Nicolas Boichat <drinkcat@...omium.org>,
        <srv_heupstream@...iatek.com>, <chao.hao@...iatek.com>,
        <linux-kernel@...r.kernel.org>, Evan Green <evgreen@...omium.org>,
        Tomasz Figa <tfiga@...gle.com>,
        <iommu@...ts.linux-foundation.org>,
        <linux-mediatek@...ts.infradead.org>,
        Krzysztof Kozlowski <krzk@...nel.org>, <anan.sun@...iatek.com>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v5 17/27] iommu/mediatek: Add pm runtime callback

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@...iatek.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
> > 
> > _______________________________________________
> > iommu mailing list
> > iommu@...ts.linux-foundation.org
> > https://lists.linuxfoundation.org/mailman/listinfo/iommu

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