linux-kernel - Re: [BUG] "access dev->iommu_fwspec" cause crash on BPI-R2

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Message-ID: <20190122164916.r343pqa2dtopzrxo@8bytes.org>
Date:   Tue, 22 Jan 2019 17:49:16 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Frank Wunderlich <frank-w@...lic-files.de>
Cc:     Matthias Brugger <matthias.bgg@...il.com>,
        iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Ryder Lee <ryder.lee@...iatek.com>
Subject: Re: [BUG] "access dev->iommu_fwspec" cause crash on BPI-R2

Hi Frank,

thanks for the report!

On Tue, Jan 22, 2019 at 05:09:09PM +0100, Frank Wunderlich wrote:
> Hi,
> 
> the following Patch breaks hdmi (at least) on Bananapi R2 (mt7623):
> 
> a9bf2eec5a6fc01a0a5250eaf0bf61dfd382a78a "iommu/mediatek: Use helper functions to access dev->iommu_fwspec"

Does the attached diff fix the issue for you?

Thanks,

	Joerg

diff --git a/drivers/iommu/mtk_iommu_v1.c b/drivers/iommu/mtk_iommu_v1.c
index 6ede4286b835..f60bdb85c4c0 100644
--- a/drivers/iommu/mtk_iommu_v1.c
+++ b/drivers/iommu/mtk_iommu_v1.c
@@ -442,6 +442,10 @@ static int mtk_iommu_add_device(struct device *dev)
 		iommu_spec.args_count = count;
 
 		mtk_iommu_create_mapping(dev, &iommu_spec);
+
+		/* dev->iommu_fwspec might have changed */
+		fwspec = dev_iommu_fwspec_get(dev);
+
 		of_node_put(iommu_spec.np);
 	}