[PATCH] iommu/mediatek-v1: Fix off-by-one in MT2701_LARB_NR_MAX

[Akari Tsuyukusa <akkun11.open@gmail.com>]

The mt2701_m4u_in_larb[] array contains 4 (for LARB0 to LARB3)
elements, meaning mt2701_m4u_to_larb() can legitimately return 3.
The current check `if (larbid >= MT2701_LARB_NR_MAX)` incorrectly
rejects valid LARB3 with -EINVAL.

Fix this off-by-one error by updating MT2701_LARB_NR_MAX to 4.

Note that this does not cause immediate issues with the current
mt2701.dtsi and mt7623n.dtsi because it only defines 3 LARBs:
    mediatek,larbs = <&larb0 &larb1 &larb2>;
Thus, larbid never reaches 3 in the existing upstream device tree.

Fixes: de78657e16f4 ("iommu/mediatek: Fix NULL pointer dereference when printing dev_name")
Signed-off-by: Akari Tsuyukusa <akkun11.open@gmail.com>
---
 drivers/iommu/mtk_iommu_v1.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/mtk_iommu_v1.c b/drivers/iommu/mtk_iommu_v1.c
index ac97dd2868d4..e907c9953142 100644
--- a/drivers/iommu/mtk_iommu_v1.c
+++ b/drivers/iommu/mtk_iommu_v1.c
@@ -88,7 +88,7 @@ struct dma_iommu_mapping {
 /* MTK generation one iommu HW only support 4K size mapping */
 #define MT2701_IOMMU_PAGE_SHIFT			12
 #define MT2701_IOMMU_PAGE_SIZE			(1UL << MT2701_IOMMU_PAGE_SHIFT)
-#define MT2701_LARB_NR_MAX			3
+#define MT2701_LARB_NR_MAX			4
 
 /*
  * MTK m4u support 4GB iova address space, and only support 4K page
-- 
2.54.0