linux-kernel - [PATCH v7 02/12] iommu/mediatek-v1: Free the existed fwspec if the master dev already has

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Date:   Fri, 30 Jul 2021 10:52:28 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     Matthias Brugger <matthias.bgg@...il.com>,
        Joerg Roedel <joro@...tes.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        David Airlie <airlied@...ux.ie>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
CC:     Evan Green <evgreen@...omium.org>,
        Robin Murphy <robin.murphy@....com>,
        Tomasz Figa <tfiga@...omium.org>,
        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>, <yong.wu@...iatek.com>,
        <youlin.pei@...iatek.com>, Nicolas Boichat <drinkcat@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>, <anan.sun@...iatek.com>,
        <ming-fan.chen@...iatek.com>, <yi.kuo@...iatek.com>,
        <acourbot@...omium.org>, <linux-media@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>, Daniel Vetter <daniel@...ll.ch>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Xia Jiang <xia.jiang@...iatek.com>,
        Tiffany Lin <tiffany.lin@...iatek.com>,
        Dafna Hirschfeld <dafna.hirschfeld@...labora.com>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Eizan Miyamoto <eizan@...omium.org>,
        <anthony.huang@...iatek.com>,
        Frank Wunderlich <frank-w@...lic-files.de>
Subject: [PATCH v7 02/12] iommu/mediatek-v1: Free the existed fwspec if the master dev already has

When the iommu master device enters of_iommu_xlate, the ops may be
NULL(iommu dev is defered), then it will initialize the fwspec here:

[<c0c9c5bc>] (dev_iommu_fwspec_set) from [<c06bda80>]
(iommu_fwspec_init+0xbc/0xd4)
[<c06bd9c4>] (iommu_fwspec_init) from [<c06c0db4>]
(of_iommu_xlate+0x7c/0x12c)
[<c06c0d38>] (of_iommu_xlate) from [<c06c10e8>]
(of_iommu_configure+0x144/0x1e8)

BUT the mtk_iommu_v1.c only supports arm32, the probing flow still is a bit
weird. We always expect create the fwspec internally. otherwise it will
enter here and return fail.

static int mtk_iommu_create_mapping(struct device *dev,
				    struct of_phandle_args *args)
{
        ...
	if (!fwspec) {
	        ....
	} else if (dev_iommu_fwspec_get(dev)->ops != &mtk_iommu_ops) {
                >>>>>>>>>>Enter here. return fail.<<<<<<<<<<<<
		return -EINVAL;
	}
	...
}

Thus, Free the existed fwspec if the master device already has fwspec.

This issue is reported at:
https://lore.kernel.org/linux-mediatek/trinity-7d9ebdc9-4849-4d93-bfb5-429dcb4ee449-1626253158870@3c-app-gmx-bs01/

Reported-by: Frank Wunderlich <frank-w@...lic-files.de>
Signed-off-by: Yong Wu <yong.wu@...iatek.com>
---
No need fix tag, since it is ok before this cleanup patchset.
the issue may be revealed by the patch adding probe_defer what adjust the
device probing sequency.
---
 drivers/iommu/mtk_iommu_v1.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/iommu/mtk_iommu_v1.c b/drivers/iommu/mtk_iommu_v1.c
index 778e66f5f1aa..6861eeab182d 100644
--- a/drivers/iommu/mtk_iommu_v1.c
+++ b/drivers/iommu/mtk_iommu_v1.c
@@ -426,6 +426,15 @@ static struct iommu_device *mtk_iommu_probe_device(struct device *dev)
 	struct mtk_iommu_data *data;
 	int err, idx = 0;
 
+	/*
+	 * In the deferred case, free the existed fwspec if the dev already has,
+	 * Always initialize the fwspec internally.
+	 */
+	if (fwspec) {
+		iommu_fwspec_free(dev);
+		fwspec = dev_iommu_fwspec_get(dev);
+	}
+
 	while (!of_parse_phandle_with_args(dev->of_node, "iommus",
 					   "#iommu-cells",
 					   idx, &iommu_spec)) {
-- 
2.18.0