Re: [PATCH v8 03/12] iommu/mediatek: Add probe_defer for smi-larb

[Dafna Hirschfeld <dafna.hirschfeld@xxxxxxxxxxxxx>]

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@xxxxxxxxxxxx>
> Tested-by: Frank Wunderlich <frank-w@xxxxxxxxxxxxxxx> # 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;
>   		}