iommu/mediatek: Improve comment for the current region/bank

No functional change. Just add more comment about the current region/bank
in the code.

Signed-off-by: Yong Wu <yong.wu@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20230411093144.2690-4-yong.wu@mediatek.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: YongWu-HF

drivers/iommu/mtk_iommu.c

@@ -197,12 +197,33 @@ struct mtk_iommu_plat_data {
 
 	char			*pericfg_comp_str;
 	struct list_head	*hw_list;
-	unsigned int		iova_region_nr;
-	const struct mtk_iommu_iova_region	*iova_region;
 
-	u8                  banks_num;
-	bool                banks_enable[MTK_IOMMU_BANK_MAX];
-	unsigned int        banks_portmsk[MTK_IOMMU_BANK_MAX];
+	/*
+	 * The IOMMU HW may support 16GB iova. In order to balance the IOVA ranges,
+	 * different masters will be put in different iova ranges, for example vcodec
+	 * is in 4G-8G and cam is in 8G-12G. Meanwhile, some masters may have the
+	 * special IOVA range requirement, like CCU can only support the address
+	 * 0x40000000-0x44000000.
+	 * Here list the iova ranges this SoC supports and which larbs/ports are in
+	 * which region.
+	 *
+	 * 16GB iova all use one pgtable, but each a region is a iommu group.
+	 */
+	struct {
+		unsigned int	iova_region_nr;
+		const struct mtk_iommu_iova_region	*iova_region;
+	};
+
+	/*
+	 * The IOMMU HW may have 5 banks. Each bank has a independent pgtable.
+	 * Here list how many banks this SoC supports/enables and which ports are in which bank.
+	 */
+	struct {
+		u8		banks_num;
+		bool		banks_enable[MTK_IOMMU_BANK_MAX];
+		unsigned int	banks_portmsk[MTK_IOMMU_BANK_MAX];
+	};
+
 	unsigned char       larbid_remap[MTK_LARB_COM_MAX][MTK_LARB_SUBCOM_MAX];
 };