linux-kernel - Re: [PATCH v2 02/12] iommu/mediatek: Add probe

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Date:   Sat, 22 Jun 2019 10:42:47 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     Matthias Brugger <matthias.bgg@...il.com>
CC:     Joerg Roedel <joro@...tes.org>, Rob Herring <robh+dt@...nel.org>,
        "Evan Green" <evgreen@...omium.org>,
        Robin Murphy <robin.murphy@....com>,
        "Tomasz Figa" <tfiga@...gle.com>,
        Will Deacon <will.deacon@....com>,
        <linux-mediatek@...ts.infradead.org>,
        <srv_heupstream@...iatek.com>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <iommu@...ts.linux-foundation.org>, <yingjoe.chen@...iatek.com>,
        <youlin.pei@...iatek.com>, Nicolas Boichat <drinkcat@...omium.org>,
        <anan.sun@...iatek.com>
Subject: Re: [PATCH v2 02/12] iommu/mediatek: Add probe_defer for smi-larb


On Wed, 2019-06-19 at 15:52 +0200, Matthias Brugger wrote:
> 
> On 10/06/2019 14:55, Yong Wu wrote:
> > The iommu consumer should use device_link to connect with the
> > smi-larb(supplier). then the smi-larb should run before the iommu
> > consumer. Here we delay the iommu driver until the smi driver is
> > ready, then all the iommu consumer always is after the smi driver.
> > 
> > When there is no this patch, if some consumer drivers run before
> > smi-larb, the supplier link_status is DL_DEV_NO_DRIVER(0) in the
> > device_link_add, then device_links_driver_bound will use WARN_ON
> > to complain that the link_status of supplier is not right.
> > 
> > This is a preparing patch for adding device_link.
> > 
> > Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> > ---
> >  drivers/iommu/mtk_iommu.c    | 2 +-
> >  drivers/iommu/mtk_iommu_v1.c | 2 +-
> >  2 files changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> > index 6fe3369..f7599d8 100644
> > --- a/drivers/iommu/mtk_iommu.c
> > +++ b/drivers/iommu/mtk_iommu.c
> > @@ -664,7 +664,7 @@ static int mtk_iommu_probe(struct platform_device *pdev)
> >  			id = i;
> >  
> >  		plarbdev = of_find_device_by_node(larbnode);
> > -		if (!plarbdev) {
> > +		if (!plarbdev || !plarbdev->dev.driver) {
> 
> can't we use:
> device_lock()
> device_is_bound(struct device *dev)
> device_unlock()

A new API for me. Thanks the hint. I have tried. it is ok.


> 
> >  			of_node_put(larbnode);
> >  			return -EPROBE_DEFER;
> >  		}
> > diff --git a/drivers/iommu/mtk_iommu_v1.c b/drivers/iommu/mtk_iommu_v1.c
> > index 0b0908c..c43c4a0 100644
> > --- a/drivers/iommu/mtk_iommu_v1.c
> > +++ b/drivers/iommu/mtk_iommu_v1.c
> > @@ -604,7 +604,7 @@ static int mtk_iommu_probe(struct platform_device *pdev)
> >  			plarbdev = of_platform_device_create(
> >  						larb_spec.np, NULL,
> >  						platform_bus_type.dev_root);
> > -			if (!plarbdev) {
> > +			if (!plarbdev || !plarbdev->dev.driver) {
> >  				of_node_put(larb_spec.np);
> >  				return -EPROBE_DEFER;
> >  			}
> >