[RFC PATCH v4 30/38] arm64: dts: renesas: Add Spider RC/EP DTs for NTB with remote DW PCIe eDMA

Koichiro Den
2026-01-18T13:55:52Z

Add dedicated DTs for the Spider CPU+BreakOut boards when used in PCIe
RC/EP mode with DW PCIe eDMA based NTB transport.

* r8a779f0-spider-rc.dts describes the board in RC mode.

It reserves 4 MiB of IOVA starting at 0xfe000000, which on this SoC
is the ECAM/Config aperture of the PCIe host bridge. In stress
testing with the remote eDMA, allowing generic DMA mappings to occupy
this range led to immediate instability. The exact mechanism is under
investigation, but reserving the range avoids the issue in practice.

* r8a779f0-spider-ep.dts describes the board in EP mode.

The RC interface is disabled and the EP interface is enabled. IPMMU
usage matches the RC case.

The base r8a779f0-spider.dts is intentionally left unchanged and
continues to describe the default RC-only board configuration.

Signed-off-by: Koichiro Den <den@valinux.co.jp>
---
arch/arm64/boot/dts/renesas/Makefile | 2 +
.../boot/dts/renesas/r8a779f0-spider-ep.dts | 37 +++++++++++++
.../boot/dts/renesas/r8a779f0-spider-rc.dts | 52 +++++++++++++++++++
3 files changed, 91 insertions(+)
create mode 100644 arch/arm64/boot/dts/renesas/r8a779f0-spider-ep.dts
create mode 100644 arch/arm64/boot/dts/renesas/r8a779f0-spider-rc.dts

diff --git a/arch/arm64/boot/dts/renesas/Makefile b/arch/arm64/boot/dts/renesas/Makefile
index 1fab1b50f20e..e8d312be515b 100644
--- a/arch/arm64/boot/dts/renesas/Makefile
+++ b/arch/arm64/boot/dts/renesas/Makefile
@@ -82,6 +82,8 @@ dtb-$(CONFIG_ARCH_R8A77995) += r8a77995-draak-panel-aa104xd12.dtb
dtb-$(CONFIG_ARCH_R8A779A0) += r8a779a0-falcon.dtb

dtb-$(CONFIG_ARCH_R8A779F0) += r8a779f0-spider.dtb
+dtb-$(CONFIG_ARCH_R8A779F0) += r8a779f0-spider-ep.dtb
+dtb-$(CONFIG_ARCH_R8A779F0) += r8a779f0-spider-rc.dtb
dtb-$(CONFIG_ARCH_R8A779F0) += r8a779f4-s4sk.dtb

dtb-$(CONFIG_ARCH_R8A779G0) += r8a779g0-white-hawk.dtb
diff --git a/arch/arm64/boot/dts/renesas/r8a779f0-spider-ep.dts b/arch/arm64/boot/dts/renesas/r8a779f0-spider-ep.dts
new file mode 100644
index 000000000000..6753f8497d0d
--- /dev/null
+++ b/arch/arm64/boot/dts/renesas/r8a779f0-spider-ep.dts
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: (GPL-2.0 OR MIT)
+/*
+ * Device Tree Source for the Spider CPU and BreakOut boards
+ * (PCIe EP mode with DW PCIe eDMA used for NTB transport)
+ *
+ * Based on the base r8a779f0-spider.dts.
+ *
+ * Copyright (C) 2025 Renesas Electronics Corp.
+ */
+
+/dts-v1/;
+#include "r8a779f0-spider-cpu.dtsi"
+#include "r8a779f0-spider-ethernet.dtsi"
+
+/ {
+ model = "Renesas Spider CPU and Breakout boards based on r8a779f0";
+ compatible = "renesas,spider-breakout", "renesas,spider-cpu",
+ "renesas,r8a779f0";
+};
+
+&i2c4 {
+ eeprom@51 {
+ compatible = "rohm,br24g01", "atmel,24c01";
+ label = "breakout-board";
+ reg = <0x51>;
+ pagesize = <8>;
+ };
+};
+
+&pciec0 {
+ status = "disabled";
+};
+
+&pciec0_ep {
+ iommus = <&ipmmu_hc 32>;
+ status = "okay";
+};
diff --git a/arch/arm64/boot/dts/renesas/r8a779f0-spider-rc.dts b/arch/arm64/boot/dts/renesas/r8a779f0-spider-rc.dts
new file mode 100644
index 000000000000..c7112862e1e1
--- /dev/null
+++ b/arch/arm64/boot/dts/renesas/r8a779f0-spider-rc.dts
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: (GPL-2.0 OR MIT)
+/*
+ * Device Tree Source for the Spider CPU and BreakOut boards
+ * (PCIe RC mode with remote DW PCIe eDMA used for NTB transport)
+ *
+ * Based on the base r8a779f0-spider.dts.
+ *
+ * Copyright (C) 2025 Renesas Electronics Corp.
+ */
+
+/dts-v1/;
+#include "r8a779f0-spider-cpu.dtsi"
+#include "r8a779f0-spider-ethernet.dtsi"
+
+/ {
+ model = "Renesas Spider CPU and Breakout boards based on r8a779f0";
+ compatible = "renesas,spider-breakout", "renesas,spider-cpu",
+ "renesas,r8a779f0";
+
+ reserved-memory {
+ #address-cells = <2>;
+ #size-cells = <2>;
+ ranges;
+
+ /*
+ * Reserve 4 MiB of IOVA starting at 0xfe000000. Allowing DMA
+ * writes whose DAR (destination IOVA) falls numerically inside
+ * the ECAM/config window has been observed to trigger
+ * controller misbehavior.
+ */
+ pciec0_iova_resv: pcie-iova-resv {
+ iommu-addresses = <&pciec0 0x0 0xfe000000 0x0 0x00400000>;
+ };
+ };
+};
+
+&i2c4 {
+ eeprom@51 {
+ compatible = "rohm,br24g01", "atmel,24c01";
+ label = "breakout-board";
+ reg = <0x51>;
+ pagesize = <8>;
+ };
+};
+
+&pciec0 {
+ iommus = <&ipmmu_hc 32>;
+ iommu-map = <0 &ipmmu_hc 32 1>;
+ iommu-map-mask = <0>;
+
+ memory-region = <&pciec0_iova_resv>;
+};
--
2.51.0