[d-kernel] [PATCH 28/30] arm64: dts: rockchip: disable IOMMU when running rk3588 in PCIe endpoint mode

[Anton Midyukov <antohami@altlinux.org>]

From: Niklas Cassel <cassel@kernel.org>

Commit da92d3dfc871 ("arm64: dts: rockchip: enable the mmu600_pcie IOMMU
on the rk3588 SoC") enabled the mmu600_pcie IOMMU, both in the normal case
(when all PCIe controllers are running in Root Complex mode) and in the
case when running the pcie3x4 PCIe controller in Endpoint mode.

There have been no issues detected when running the PCIe controllers in
Root Complex mode. During PCI probe time, we will add a SID to the IOMMU
for each PCI device enumerated on the bus, including the root port itself.

However, when running the pcie3x4 PCIe controller in Endpoint mode, we
will only add a single SID to the IOMMU (the SID specified in the iommus
DT property).

The enablement of IOMMU in endpoint mode was verified on setup with two
Rock 5b:s, where the BDF of the Root Complex has BDF (00:00.0).

A Root Complex sending a TLP to the Endpoint will have Requester ID set
to the BDF of the initiator. On the EP side, the Requester ID will then
be used as the SID. This works fine if the Root Complex has a BDF that
matches the iommus DT property, however, if the Root Complex has any other
BDF, we will see something like:
arm-smmu-v3 fc900000.iommu: event: C_BAD_STREAMID client: (unassigned sid) sid: 0x1600 ssid: 0x0
on the endpoint side.

For PCIe controllers running in endpoint mode that always uses the
incoming Requester ID as the SID, the iommus DT property simply isn't
a viable solution. (Neither is iommu-map a viable solution, as there is
no enumeration done on the endpoint side.)

Thus, partly revert commit da92d3dfc871 ("arm64: dts: rockchip: enable the
mmu600_pcie IOMMU on the rk3588 SoC") by disabling the PCI IOMMU when
running the pcie3x4 PCIe controller in Endpoint mode.

Since the PCI IOMMU is working as expected in the normal case, keep it
enabled when running all PCIe controllers in Root Complex mode.

Fixes: da92d3dfc871 ("arm64: dts: rockchip: enable the mmu600_pcie IOMMU on the rk3588 SoC")
Signed-off-by: Niklas Cassel <cassel@kernel.org>
Acked-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/20250207143900.2047949-2-cassel@kernel.org
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
(cherry picked from commit 7d1163fc08936fcb5cf5d9daf366c322c3b4e882)
Signed-off-by: Anton Midyukov <antohami@altlinux.org>
---
 arch/arm64/boot/dts/rockchip/rk3588-extra.dtsi           | 1 -
 arch/arm64/boot/dts/rockchip/rk3588-rock-5b-pcie-ep.dtso | 4 ++++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/boot/dts/rockchip/rk3588-extra.dtsi b/arch/arm64/boot/dts/rockchip/rk3588-extra.dtsi
index 4a950907ea6f5..840b638af1c24 100644
--- a/arch/arm64/boot/dts/rockchip/rk3588-extra.dtsi
+++ b/arch/arm64/boot/dts/rockchip/rk3588-extra.dtsi
@@ -213,7 +213,6 @@ pcie3x4_ep: pcie-ep@fe150000 {
 		interrupt-names = "sys", "pmc", "msg", "legacy", "err",
 				  "dma0", "dma1", "dma2", "dma3";
 		max-link-speed = <3>;
-		iommus = <&mmu600_pcie 0x0000>;
 		num-lanes = <4>;
 		phys = <&pcie30phy>;
 		phy-names = "pcie-phy";
diff --git a/arch/arm64/boot/dts/rockchip/rk3588-rock-5b-pcie-ep.dtso b/arch/arm64/boot/dts/rockchip/rk3588-rock-5b-pcie-ep.dtso
index 672d748fcc67c..f229cb49da680 100644
--- a/arch/arm64/boot/dts/rockchip/rk3588-rock-5b-pcie-ep.dtso
+++ b/arch/arm64/boot/dts/rockchip/rk3588-rock-5b-pcie-ep.dtso
@@ -23,3 +23,7 @@ &pcie3x4_ep {
 	vpcie3v3-supply = <&vcc3v3_pcie30>;
 	status = "okay";
 };
+
+&mmu600_pcie {
+	status = "disabled";
+};
-- 
2.42.4