The MMU_CTRL register of MT8173 is different from other SoCs.
The in_order_wr_en is bit[9] which is zero by default.
Other SoCs have the vitcim_tlb_en feature mapped to bit[12].
This bit is set to one by default. We need to preserve the bit
when setting F_MMU_TF_PROT_TO_PROGRAM_ADDR as otherwise the
bit will be cleared and IOMMU performance will drop.

Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Yong Wu <yong.wu@mediatek.com>
Signed-off-by: Chao Hao <redacted>
---
 drivers/iommu/mtk_iommu.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
index e71003037ffa..a816030d00f1 100644
--- a/drivers/iommu/mtk_iommu.c
+++ b/drivers/iommu/mtk_iommu.c

@@ -555,11 +555,13 @@ static int mtk_iommu_hw_init(const struct mtk_iommu_data *data)
 		return ret;
 	}
 
-	if (data->plat_data->m4u_plat == M4U_MT8173)
+	if (data->plat_data->m4u_plat == M4U_MT8173) {
 		regval = F_MMU_PREFETCH_RT_REPLACE_MOD |
 			 F_MMU_TF_PROT_TO_PROGRAM_ADDR_MT8173;
-	else
-		regval = F_MMU_TF_PROT_TO_PROGRAM_ADDR;
+	} else {
+		regval = readl_relaxed(data->base + REG_MMU_CTRL_REG);
+		regval |= F_MMU_TF_PROT_TO_PROGRAM_ADDR;
+	}
 	writel_relaxed(regval, data->base + REG_MMU_CTRL_REG);
 
 	regval = F_L2_MULIT_HIT_EN |

-- 
2.18.0