[PATCH v6 21/22] iommu/mediatek: Fix iova_to_phys PA start for 4GB mode

[Yong Wu]

In the 4GB mode, the physical address is remapped,

Here is the detailed remap relationship.
CPU PA         ->    HW PA
0x4000_0000          0x1_4000_0000 (Add bit32)
0x8000_0000          0x1_8000_0000 ...
0xc000_0000          0x1_c000_0000 ...
0x1_0000_0000        0x1_0000_0000 (No change)

Thus, we always add bit32 for PA when entering mtk_iommu_map.
But in the iova_to_phys, the CPU don't need this bit32 if the
PA is from 0x1_4000_0000 to 0x1_ffff_ffff.
This patch discards the bit32 in this iova_to_phys in the 4GB mode.

Signed-off-by: Yong Wu <yong.wu@xxxxxxxxxxxx>
---
 drivers/iommu/mtk_iommu.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
index 0277396..076d333 100644
--- a/drivers/iommu/mtk_iommu.c
+++ b/drivers/iommu/mtk_iommu.c
@@ -119,6 +119,19 @@ struct mtk_iommu_domain {
 
 static const struct iommu_ops mtk_iommu_ops;
 
+/*
+ * In M4U 4GB mode, the physical address is remapped as below:
+ *  CPU PA         ->   M4U HW PA
+ *  0x4000_0000         0x1_4000_0000 (Add bit32)
+ *  0x8000_0000         0x1_8000_0000 ...
+ *  0xc000_0000         0x1_c000_0000 ...
+ *  0x1_0000_0000       0x1_0000_0000 (No change)
+ *
+ * Thus, We always add BIT32 in the iommu_map and disable BIT32 if PA is >=
+ * 0x1_4000_0000 in the iova_to_phys.
+ */
+#define MTK_IOMMU_4GB_MODE_PA_140000000     0x140000000UL
+
 static LIST_HEAD(m4ulist);	/* List all the M4U HWs */
 
 #define for_each_m4u(data)	list_for_each_entry(data, &m4ulist, list)
@@ -415,6 +428,7 @@ static phys_addr_t mtk_iommu_iova_to_phys(struct iommu_domain *domain,
 					  dma_addr_t iova)
 {
 	struct mtk_iommu_domain *dom = to_mtk_domain(domain);
+	struct mtk_iommu_data *data = mtk_iommu_get_m4u_data();
 	unsigned long flags;
 	phys_addr_t pa;
 
@@ -422,6 +436,10 @@ static phys_addr_t mtk_iommu_iova_to_phys(struct iommu_domain *domain,
 	pa = dom->iop->iova_to_phys(dom->iop, iova);
 	spin_unlock_irqrestore(&dom->pgtlock, flags);
 
+	if (data->plat_data->has_4gb_mode && data->dram_is_4gb &&
+	    pa >= MTK_IOMMU_4GB_MODE_PA_140000000)
+		pa &= ~BIT_ULL(32);
+
 	return pa;
 }
 
-- 
1.9.1