6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Johan Hovold <johan@kernel.org>

commit c77ad28bfee0df9cbc719eb5adc9864462cfb65b upstream.

Make sure to drop the reference taken to the iommu platform device when
looking up its driver data during probe_device().

Fixes: b17336c55d89 ("iommu/mediatek: add support for mtk iommu generation one HW")
Cc: stable@vger.kernel.org	# 4.8
Cc: Honghui Zhang <redacted>
Acked-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Yong Wu <yong.wu@mediatek.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Joerg Roedel <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/iommu/mtk_iommu_v1.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/iommu/mtk_iommu_v1.c
+++ b/drivers/iommu/mtk_iommu_v1.c

@@ -422,6 +422,8 @@ static int mtk_iommu_v1_create_mapping(s
 			return -EINVAL;
 
 		dev_iommu_priv_set(dev, platform_get_drvdata(m4updev));
+
+		put_device(&m4updev->dev);
 	}
 
 	ret = iommu_fwspec_add_ids(dev, args->args, 1);