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    SubjectRe: [PATCH v8 03/12] iommu/mediatek: Add probe_defer for smi-larb
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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;
    > }
    >

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