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Subject: Re: [PATCH v8 03/12] iommu/mediatek: Add probe_defer for smi-larb
To:     Yong Wu <yong.wu@mediatek.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Joerg Roedel <joro@8bytes.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
        David Airlie <airlied@linux.ie>,
        Mauro Carvalho Chehab <mchehab@kernel.org>
Cc:     Evan Green <evgreen@chromium.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Tomasz Figa <tfiga@chromium.org>,
        Will Deacon <will.deacon@arm.com>,
        linux-mediatek@lists.infradead.org, srv_heupstream@mediatek.com,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        iommu@lists.linux-foundation.org, youlin.pei@mediatek.com,
        Matthias Kaehlcke <mka@chromium.org>, anan.sun@mediatek.com,
        yi.kuo@mediatek.com, acourbot@chromium.org,
        linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
        Daniel Vetter <daniel@ffwll.ch>,
        Chun-Kuang Hu <chunkuang.hu@kernel.org>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Tiffany Lin <tiffany.lin@mediatek.com>,
        Hsin-Yi Wang <hsinyi@chromium.org>,
        Eizan Miyamoto <eizan@chromium.org>,
        anthony.huang@mediatek.com,
        Frank Wunderlich <frank-w@public-files.de>
References: <20210929013719.25120-1-yong.wu@mediatek.com>
 <20210929013719.25120-4-yong.wu@mediatek.com>
From:   Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Message-ID: <33a8b313-ad1b-d307-7e8c-2fdebdc6f1a7@collabora.com>
Date:   Wed, 29 Sep 2021 18:33:05 +0200
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On 29.09.21 03:37, Yong Wu wrote:
> Prepare for adding device_link.
> 
> 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 consumers always are 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.
> 
> device_is_bound may be more elegant here. but it is not allowed to
> EXPORT from https://lore.kernel.org/patchwork/patch/1334670/.
> 
> Signed-off-by: Yong Wu <yong.wu@mediatek.com>
> Tested-by: Frank Wunderlich <frank-w@public-files.de> # BPI-R2/MT7623
> ---
>   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 d837adfd1da5..d5848f78a677 100644
> --- a/drivers/iommu/mtk_iommu.c
> +++ b/drivers/iommu/mtk_iommu.c
> @@ -844,7 +844,7 @@ 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) {
>   			of_node_put(larbnode);
>   			return -EPROBE_DEFER;

if plarbdev is null doesn't that mean that the device does not exist?
so we should return -ENODEV in that case?

thanks,
Dafna

>   		}
> diff --git a/drivers/iommu/mtk_iommu_v1.c b/drivers/iommu/mtk_iommu_v1.c
> index 1467ba1e4417..4d7809432239 100644
> --- a/drivers/iommu/mtk_iommu_v1.c
> +++ b/drivers/iommu/mtk_iommu_v1.c
> @@ -602,7 +602,7 @@ static int mtk_iommu_probe(struct platform_device *pdev)
>   		}
>   
>   		plarbdev = of_find_device_by_node(larbnode);
> -		if (!plarbdev) {
> +		if (!plarbdev || !plarbdev->dev.driver) {
>   			of_node_put(larbnode);
>   			return -EPROBE_DEFER;
>   		}
>