Add IOMMU GFP_DMA32 patch for RK3568 8GB systems

Force GFP_DMA32 allocation for Rockchip IOMMU v2 page tables to fix
NPU operation on systems with >4GB RAM. Without this patch, IOMMU
allocates page tables above 4GB which the NPU cannot access, causing
DMA mapping failures.

Tested on ODROID-M1 with 8GB RAM, kernel 6.18.9-current-rockchip64.

Author: vitalijborissow

patch/kernel/rockchip64-current/0001-iommu-rockchip-force-DMA32-for-rk3568-iommu-v2.patch

@@ -0,0 +1,37 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Vitalij Borissow <250549977+vitalijborissow@users.noreply.github.com>
+Date: Sat, 15 Feb 2026 21:30:00 +0100
+Subject: iommu/rockchip: Force GFP_DMA32 for rk3568-iommu v2
+
+On systems with >4GB RAM, the RK3568 IOMMU v2 allocates page tables from
+high memory (above 4GB). While the IOMMU claims 40-bit address support,
+some devices like the NPU cannot properly handle page tables located
+above 4GB, resulting in DMA mapping failures and NPU timeouts.
+
+This patch forces GFP_DMA32 allocation for IOMMU v2 page tables,
+ensuring all allocations are within the first 4GB of physical memory.
+
+Tested on ODROID-M1 with 8GB RAM running kernel 6.18.9-current-rockchip64.
+Without this patch, NPU inference fails with IOMMU page table access errors.
+With this patch, NPU operates correctly with full IOMMU support enabled.
+
+Signed-off-by: Vitalij Borissow <250549977+vitalijborissow@users.noreply.github.com>
+---
+ drivers/iommu/rockchip-iommu.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
+index 111111111111..222222222222 100644
+--- a/drivers/iommu/rockchip-iommu.c
++++ b/drivers/iommu/rockchip-iommu.c
+@@ -1349,7 +1349,7 @@ static struct rk_iommu_ops iommu_data_ops_v2 = {
+ 	.mk_dtentries = &rk_mk_dte_v2,
+ 	.mk_ptentries = &rk_mk_pte_v2,
+ 	.dma_bit_mask = DMA_BIT_MASK(40),
+-	.gfp_flags = 0,
++	.gfp_flags = GFP_DMA32,
+ };
+ 
+ static const struct of_device_id rk_iommu_dt_ids[] = {
+-- 
+Armbian