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Thu, 04 Jun 2026 06:53:01 -0700 (PDT) From: Midgy BALON To: tomeu@tomeuvizoso.net, ogabbay@kernel.org, heiko@sntech.de, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, joro@8bytes.org, will@kernel.org Cc: robin.murphy@arm.com, dri-devel@lists.freedesktop.org, linux-rockchip@lists.infradead.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [RFC PATCH v3 6/9] iommu/rockchip: Clear AUTO_GATING bit 1 on the RK356x v1 IOMMU Date: Thu, 4 Jun 2026 13:52:52 +0000 Message-Id: <20260604135255.62682-7-midgy971@gmail.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20260604135255.62682-1-midgy971@gmail.com> References: <20260604135255.62682-1-midgy971@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- 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: -- 2.39.5