linux-kernel - Re: [PATCH v4 3/6] iommu/mediatek: Add error path for loop of mm_dts

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Date:   Tue, 30 Aug 2022 10:14:49 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Yong Wu <yong.wu@...iatek.com>, Joerg Roedel <joro@...tes.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Will Deacon <will@...nel.org>
Cc:     Robin Murphy <robin.murphy@....com>, iommu@...ts.linux.dev,
        iommu@...ts.linux-foundation.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        mingyuan.ma@...iatek.com, yf.wang@...iatek.com,
        libo.kang@...iatek.com, chengci.xu@...iatek.com,
        youlin.pei@...iatek.com, anan.sun@...iatek.com,
        xueqi.zhang@...iatek.com, Guenter Roeck <groeck@...omium.org>,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH v4 3/6] iommu/mediatek: Add error path for loop of
 mm_dts_parse

Il 24/08/22 08:43, Yong Wu ha scritto:
> The mtk_iommu_mm_dts_parse will parse the smi larbs nodes. if the i+1
> larb is parsed fail, we should put_device for the 0..i larbs.
> 
> There are two places need to comment:
> 1) The larbid may be not linear mapping, we should loop whole
>     the array in the error path.
> 2) I move this line position: "data->larb_imu[id].dev = &plarbdev->dev;"
>     That means set data->larb_imu[id].dev before the error path.
>     then we don't need "platform_device_put(plarbdev)" again while
>     probe_defer case. All depend on "put_device" in the error path in error
>     cases.
> 
> Fixes: d2e9a1102cfc ("iommu/mediatek: Contain MM IOMMU flow with the MM TYPE")
> Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> ---
>   drivers/iommu/mtk_iommu.c | 42 ++++++++++++++++++++++++++++-----------
>   1 file changed, 30 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> index 9c5902207bef..f63d4210043d 100644
> --- a/drivers/iommu/mtk_iommu.c
> +++ b/drivers/iommu/mtk_iommu.c
> @@ -1053,8 +1053,10 @@ static int mtk_iommu_mm_dts_parse(struct device *dev, struct component_match **m
>   		u32 id;
>   
>   		larbnode = of_parse_phandle(dev->of_node, "mediatek,larbs", i);
> -		if (!larbnode)
> -			return -EINVAL;
> +		if (!larbnode) {
> +			ret = -EINVAL;
> +			goto err_larbdev_put;
> +		}
>   
>   		if (!of_device_is_available(larbnode)) {
>   			of_node_put(larbnode);
> @@ -1067,14 +1069,16 @@ static int mtk_iommu_mm_dts_parse(struct device *dev, struct component_match **m
>   
>   		plarbdev = of_find_device_by_node(larbnode);
>   		of_node_put(larbnode);
> -		if (!plarbdev)
> -			return -ENODEV;
> +		if (!plarbdev) {
> +			ret = -ENODEV;
> +			goto err_larbdev_put;
> +		}
> +		data->larb_imu[id].dev = &plarbdev->dev;
>   
>   		if (!plarbdev->dev.driver) {
> -			platform_device_put(plarbdev);
> -			return -EPROBE_DEFER;
> +			ret = -EPROBE_DEFER;
> +			goto err_larbdev_put;
>   		}
> -		data->larb_imu[id].dev = &plarbdev->dev;
>   
>   		component_match_add(dev, match, component_compare_dev, &plarbdev->dev);
>   		platform_device_put(plarbdev);
> @@ -1082,8 +1086,10 @@ static int mtk_iommu_mm_dts_parse(struct device *dev, struct component_match **m
>   
>   	/* Get smi-(sub)-common dev from the last larb. */
>   	smi_subcomm_node = of_parse_phandle(larbnode, "mediatek,smi", 0);
> -	if (!smi_subcomm_node)
> -		return -EINVAL;
> +	if (!smi_subcomm_node) {
> +		ret = -EINVAL;
> +		goto err_larbdev_put;
> +	}
>   
>   	/*
>   	 * It may have two level smi-common. the node is smi-sub-common if it
> @@ -1097,8 +1103,10 @@ static int mtk_iommu_mm_dts_parse(struct device *dev, struct component_match **m
>   
>   	pcommdev = of_find_device_by_node(smicomm_node);
>   	of_node_put(smicomm_node);
> -	if (!pcommdev)
> -		return -EINVAL;
> +	if (!pcommdev) {
> +		ret = -EINVAL;
> +		goto err_larbdev_put;
> +	}
>   	data->smicomm_dev = &pcommdev->dev;
>   
>   	link = device_link_add(data->smicomm_dev, dev,
> @@ -1106,9 +1114,19 @@ static int mtk_iommu_mm_dts_parse(struct device *dev, struct component_match **m
>   	platform_device_put(pcommdev);
>   	if (!link) {
>   		dev_err(dev, "Unable to link %s.\n", dev_name(data->smicomm_dev));
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		goto err_larbdev_put;
>   	}
>   	return 0;
> +
> +err_larbdev_put:
> +	/* id may be not linear mapping, loop whole the array */
> +	for (i = 0; i < MTK_LARB_NR_MAX; i++) {

Since there may be a case in which the mapping is linear and we're doing teardown,
I think it would be sensible to loop the other way around instead, from
MTK_LARB_NR_MAX to 0.

Everything else looks good to me.

Cheers,
Angelo

> +		if (!data->larb_imu[i].dev)
> +			continue;
> +		put_device(data->larb_imu[i].dev);
> +	}
> +	return ret;
>   }
>   
>   static int mtk_iommu_probe(struct platform_device *pdev)