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

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Date:   Wed, 19 Jun 2019 15:52:40 +0200
From:   Matthias Brugger <matthias.bgg@...il.com>
To:     Yong Wu <yong.wu@...iatek.com>, Joerg Roedel <joro@...tes.org>,
        Rob Herring <robh+dt@...nel.org>
Cc:     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 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()

>  			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;
>  			}
>