linux-kernel - Re: [PATCH 04/13] iommu/mediatek: Add device_link between the consumer and the larb devices

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Date:   Wed, 13 Mar 2019 17:11:53 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     Robin Murphy <robin.murphy@....com>
CC:     Joerg Roedel <joro@...tes.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Rob Herring <robh+dt@...nel.org>, <youlin.pei@...iatek.com>,
        <devicetree@...r.kernel.org>,
        Nicolas Boichat <drinkcat@...omium.org>, <arnd@...db.de>,
        <srv_heupstream@...iatek.com>, Will Deacon <will.deacon@....com>,
        <linux-kernel@...r.kernel.org>, Tomasz Figa <tfiga@...gle.com>,
        <iommu@...ts.linux-foundation.org>,
        <linux-mediatek@...ts.infradead.org>, <yingjoe.chen@...iatek.com>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 04/13] iommu/mediatek: Add device_link between the
 consumer and the larb devices

Hi Robin,

sorry for reply so late.

On Wed, 2019-02-27 at 19:30 +0000, Robin Murphy wrote:
> On 01/01/2019 04:51, Yong Wu wrote:
> > MediaTek IOMMU don't have its power-domain. all the consumer connect
> > with smi-larb, then connect with smi-common.
> > 
> >          M4U
> >           |
> >      smi-common
> >           |
> >    -------------
> >    |         |    ...
> >    |         |
> > larb1     larb2
> >    |         |
> > vdec       venc
> > 
> > When the consumer works, it should enable the smi-larb's power which
> > also need enable the smi-common's power firstly.
> > 
> > Thus, First of all, use the device link connect the consumer and the
> > smi-larbs. then add device link between the smi-larb and smi-common.
> > 
> > This patch adds device_link between the consumer and the larbs.
> > 
> > Suggested-by: Tomasz Figa <tfiga@...omium.org>
> > Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> > ---
> >   drivers/iommu/mtk_iommu.c    | 15 +++++++++++++--
> >   drivers/iommu/mtk_iommu_v1.c | 14 ++++++++++++--
> >   2 files changed, 25 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> > index 202e41b..735ae8d 100644
> > --- a/drivers/iommu/mtk_iommu.c
> > +++ b/drivers/iommu/mtk_iommu.c
> > @@ -247,6 +247,7 @@ static void mtk_iommu_config(struct mtk_iommu_data *data,
> >   	struct mtk_smi_larb_iommu    *larb_mmu;
> >   	unsigned int                 larbid, portid;
> >   	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> > +	struct device_link *link;
> >   	int i;
> >   
> >   	for (i = 0; i < fwspec->num_ids; ++i) {
> > @@ -257,10 +258,20 @@ static void mtk_iommu_config(struct mtk_iommu_data *data,
> >   		dev_dbg(dev, "%s iommu port: %d\n",
> >   			enable ? "enable" : "disable", portid);
> >   
> > -		if (enable)
> > +		if (enable) {
> >   			larb_mmu->mmu |= MTK_SMI_MMU_EN(portid);
> > -		else
> > +			/* Link the consumer with the larb device(supplier) */
> > +			link = device_link_add(dev, larb_mmu->dev,
> > +					       DL_FLAG_PM_RUNTIME |
> > +					       DL_FLAG_AUTOREMOVE_CONSUMER);
> 
> This looks technically wrong, since we get here from 
> mtk_iommu_attach_device(), and in theory a device could get attached to 
> any number of domains over its lifetime, so adding a link at this point 
> when there's no corresponding cleanup on detach is definitely 
> unbalanced. If you want this layer to manage the link on behalf of the 
> consumer, it would probably be better to do it at the point of 
> mtk_iommu_add_device(), and either track it for manual cleanup in 
> mtk_iommu_remove_device() or rely on AUTOREMOVE_SUPPLIER.

Thanks. I will try to move the "device_link_add" in add_device in next
version.

> 
> Robin.
> 
> > +			if (!link) {
> > +				dev_err(dev, "Unable to link %s\n",
> > +					dev_name(larb_mmu->dev));
> > +				return;
> > +			}
> > +		} else {
> >   			larb_mmu->mmu &= ~MTK_SMI_MMU_EN(portid);
> > +		}
> >   	}
> >   }
> >   
> > diff --git a/drivers/iommu/mtk_iommu_v1.c b/drivers/iommu/mtk_iommu_v1.c
> > index 9386aee..022bad9 100644
> > --- a/drivers/iommu/mtk_iommu_v1.c
> > +++ b/drivers/iommu/mtk_iommu_v1.c
> > @@ -201,6 +201,7 @@ static void mtk_iommu_config(struct mtk_iommu_data *data,
> >   	struct mtk_smi_larb_iommu    *larb_mmu;
> >   	unsigned int                 larbid, portid;
> >   	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> > +	struct device_link *link;
> >   	int i;
> >   
> >   	for (i = 0; i < fwspec->num_ids; ++i) {
> > @@ -211,10 +212,19 @@ static void mtk_iommu_config(struct mtk_iommu_data *data,
> >   		dev_dbg(dev, "%s iommu port: %d\n",
> >   			enable ? "enable" : "disable", portid);
> >   
> > -		if (enable)
> > +		if (enable) {
> >   			larb_mmu->mmu |= MTK_SMI_MMU_EN(portid);
> > -		else
> > +			link = device_link_add(dev, larb_mmu->dev,
> > +					       DL_FLAG_PM_RUNTIME |
> > +					       DL_FLAG_AUTOREMOVE_CONSUMER);
> > +			if (!link) {
> > +				dev_err(dev, "Unable to link %s\n",
> > +					dev_name(larb_mmu->dev));
> > +				return;
> > +			}
> > +		} else {
> >   			larb_mmu->mmu &= ~MTK_SMI_MMU_EN(portid);
> > +		}
> >   	}
> >   }
> >   
> >