Hello Midgy,
On 6/4/2026 9:52 PM, Midgy BALON wrote:
> On the RK356x v1 IOMMU, RK_MMU_AUTO_GATING resets to 0x3. Bit 1 enables
> auto clock-gating of the page-table walker, so the walker's AXI master
> loses its clock between transactions; a TLB-miss page walk then never
> completes and the IOMMU is left stuck (PAGING_ENABLED, never IDLE).
>
> Clear bit 1 (keeping bit 0, the slave-port gate) once paging is enabled
> so the walker keeps its clock. This is required for the RK3568 NPU MMU.
>
> Signed-off-by: Midgy BALON <[email protected]>
> ---
> drivers/iommu/rockchip-iommu.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
> index 4da80136933c4..e3d8b6e9ca12b 100644
> --- a/drivers/iommu/rockchip-iommu.c
> +++ b/drivers/iommu/rockchip-iommu.c
> @@ -953,6 +953,18 @@ static int rk_iommu_enable(struct rk_iommu *iommu)
>
> ret = rk_iommu_enable_paging(iommu);
>
> + if (!ret) {
> + /*
> + * RK356x v1 IOMMU: RK_MMU_AUTO_GATING bit 1 enables page-walker
> + * auto clock-gating; the walker's AXI master then loses its
> clock
> + * between transactions and a TLB-miss page walk never
> completes,
> + * leaving the IOMMU stuck (PAGING_ENABLED, never IDLE). Clear
> + * bit 1 (keep bit 0, the slave-port gate) once paging is
> enabled.
> + */
> + for (i = 0; i < iommu->num_mmu; i++)
> + rk_iommu_write(iommu->bases[i], RK_MMU_AUTO_GATING,
> 0x2);
> + }
> +
> out_disable_stall:
> rk_iommu_disable_stall(iommu);
> out_disable_clocks:
As I said, it is v2. Could you please try using the code below
instead and see if it works? Thank you.
diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
index 0013cf196c57..89e3a83a0251 100644
--- a/drivers/iommu/rockchip-iommu.c
+++ b/drivers/iommu/rockchip-iommu.c
@@ -930,6 +930,7 @@ static int rk_iommu_enable(struct rk_iommu *iommu)
struct iommu_domain *domain = iommu->domain;
struct rk_iommu_domain *rk_domain = to_rk_domain(domain);
int ret, i;
+ u32 auto_gate;
ret = clk_bulk_enable(iommu->num_clocks, iommu->clocks);
if (ret)
@@ -948,6 +949,10 @@ static int rk_iommu_enable(struct rk_iommu *iommu)
rk_ops->mk_dtentries(rk_domain->dt_dma));
rk_iommu_base_command(iommu->bases[i], RK_MMU_CMD_ZAP_CACHE);
rk_iommu_write(iommu->bases[i], RK_MMU_INT_MASK,
RK_MMU_IRQ_MASK);
+
+ auto_gate = rk_iommu_read(iommu->bases[i], RK_MMU_AUTO_GATING);
+ auto_gate |= BIT(31);
+ rk_iommu_write(iommu->bases[i], RK_MMU_AUTO_GATING, auto_gate);
}
ret = rk_iommu_enable_paging(iommu);
--
Best,
Chaoyi
