iommu/mediatek: Add mutex for data in the mtk_iommu_domain

Same with the previous patch, add a mutex for the "data" in the
mtk_iommu_domain. Just improve the safety for multi devices
enter attach_device at the same time. We don't get the real issue
for this.
Signed-off-by: Yong Wu <yong.wu@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Link: https://lore.kernel.org/r/20220503071427.2285-9-yong.wu@mediatek.comSigned-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/mtk_iommu.c

@@ -128,6 +128,8 @@ struct mtk_iommu_domain {
 
 	struct mtk_iommu_data		*data;
 	struct iommu_domain		domain;
+
+	struct mutex			mutex; /* Protect "data" in this structure */
 };
 
 static const struct iommu_ops mtk_iommu_ops;
@@ -434,6 +436,7 @@ static struct iommu_domain *mtk_iommu_domain_alloc(unsigned type)
 	dom = kzalloc(sizeof(*dom), GFP_KERNEL);
 	if (!dom)
 		return NULL;
+	mutex_init(&dom->mutex);
 
 	return &dom->domain;
 }
@@ -455,14 +458,19 @@ static int mtk_iommu_attach_device(struct iommu_domain *domain,
 	if (domid < 0)
 		return domid;
 
+	mutex_lock(&dom->mutex);
 	if (!dom->data) {
 		/* Data is in the frstdata in sharing pgtable case. */
 		frstdata = mtk_iommu_get_m4u_data();
 
-		if (mtk_iommu_domain_finalise(dom, frstdata, domid))
+		ret = mtk_iommu_domain_finalise(dom, frstdata, domid);
+		if (ret) {
+			mutex_unlock(&dom->mutex);
 			return -ENODEV;
+		}
 		dom->data = data;
 	}
+	mutex_unlock(&dom->mutex);
 
 	mutex_lock(&data->mutex);
 	if (!data->m4u_dom) { /* Initialize the M4U HW */