Hi,

On Tue, Nov 10, 2026 at 07:11:47AM +0000, Arun Iyengar via B4 Relay wrote:
> The MMU-600 in front of the PCIe controllers of the Rockchip RK3588
> (mmu600_pcie) is enabled for every RK3588 board, but its node describes
> neither the power domain it lives in (RK3588_PD_PCIE) nor its clock
> (ACLK_MMU_PCIE). Both are held by any enabled PCIe controller, which is
> why nobody noticed: on a board that enables no PCIe controller in that
> domain (an Orange Pi 5 with its M.2 slot in SATA mode, or any RK3588
> board without PCIe), genpd powers the domain off and the clock framework
> gates the clock as unused after boot, while arm-smmu-v3 stays bound.
> At reboot, arm_smmu_device_shutdown() then writes CR0 and polls CR0ACK on
> the dead block, the interconnect stalls, "reboot: Restarting system" is
> never reached and the board only comes back ~90 s later when the
> watchdog fires.
> 
> Patches 1 and 2 allow power-domains and clocks in the arm,smmu-v3
> binding (arm,smmu.yaml already allows both for the earlier SMMUs).
> Patch 3 makes the driver get and enable the clocks of its firmware node
> before the first register access, for as long as it is bound; nodes
> without clocks (and ACPI/IORT systems) are unaffected. Patches 4 and 5
> describe the power domain and the clock in rk3588-base.dtsi. Both DT
> patches are needed: with the power domain alone the clock is still
> gated and the shutdown still hangs.
> 
> Related: Pranjal Shrivastava's "iommu/arm-smmu-v3: Add runtime PM
> support" v11 (2026-09-29, 20260929034510.2023173-1-praan@google.com,
> not merged) adds pm_domain-based runtime PM and resumes the SMMU around
> shutdown, but has no clock handling. This series is compatible with it:
> once it lands, the clocks from patch 3 should move into its runtime
> suspend/resume callbacks.
> 
> Tested on an Orange Pi 5 (RK3588S) with the M.2 slot in SATA mode and
> the root filesystem on the SATA SSD, where every reboot used to hang:
> three consecutive reboots printed "reboot: Restarting system" and the
> boot loader started 0.6 s later (previously ~89 s, from the watchdog);
> clk_summary shows aclk_mmu_pcie enabled with iommu@fc900000 as consumer
> and pm_genpd_summary shows PD_PCIE on; the SMMU probes as before and
> SATA keeps running at 6.0 Gbps without errors. With patch 4 alone
> (power domain, clock still gated) the reboot still hung at
> "arm-smmu-v3 fc900000.iommu: shutdown" on the serial console. Boards
> with PCIe enabled are already in the state these patches describe.
> 
> This series was developed with Claude (Anthropic) as a coding assistant:
> it wrote the code and the commit messages, and I reviewed and tested
> every change as described above.
> 
> Signed-off-by: Arun Iyengar <aiyengar1990@gmail.com>
> ---

While at it, maybe also add the reset line (SRST_A_MMU_PCIE on
RK3588) to make the hardware description complete? See also the
MMU-600 TRM, that there is one clock and one reset line:

Link: https://support.arm.com/documentation/100310/0202/Signal-descriptions/Clock-and-reset-signals?lang=en

Greetings,

-- Sebastian