[PATCH v6 7/7] arm64: dts: ti: iot2050: Add overlay for DMA isolation for devices behind PCI RC

[Jan Kiszka]

From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>

Reserve a 64M memory region and ensure that all PCI devices do their DMA
only inside that region. This is configured via a restricted-dma-pool
and enforced with the help of the first PVU.

Applying this isolation is not totally free in terms of overhead and
memory consumption. It  makes only sense for variants that support
secure booting, and generally only when this is actually enable.
Therefore model it as overlay that can be activated on demand. The
firmware will take care of this via DT fixup during boot and will also
provide a way to adjust the pool size.

Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
---
 arch/arm64/boot/dts/ti/Makefile               |  5 +++
 ...am6548-iot2050-advanced-dma-isolation.dtso | 33 +++++++++++++++++++
 2 files changed, 38 insertions(+)
 create mode 100644 arch/arm64/boot/dts/ti/k3-am6548-iot2050-advanced-dma-isolation.dtso

diff --git a/arch/arm64/boot/dts/ti/Makefile b/arch/arm64/boot/dts/ti/Makefile
index bcd392c3206e..b6ee943be8c6 100644
--- a/arch/arm64/boot/dts/ti/Makefile
+++ b/arch/arm64/boot/dts/ti/Makefile
@@ -74,8 +74,10 @@ k3-am654-gp-evm-dtbs := k3-am654-base-board.dtb \
 k3-am654-evm-dtbs := k3-am654-base-board.dtb k3-am654-icssg2.dtbo
 k3-am654-idk-dtbs := k3-am654-evm.dtb k3-am654-idk.dtbo k3-am654-pcie-usb2.dtbo
 k3-am6548-iot2050-advanced-m2-bkey-ekey-pcie-dtbs := k3-am6548-iot2050-advanced-m2.dtb \
+	k3-am6548-iot2050-advanced-dma-isolation.dtbo \
 	k3-am6548-iot2050-advanced-m2-bkey-ekey-pcie.dtbo
 k3-am6548-iot2050-advanced-m2-bkey-usb3-dtbs := k3-am6548-iot2050-advanced-m2.dtb \
+	k3-am6548-iot2050-advanced-dma-isolation.dtbo \
 	k3-am6548-iot2050-advanced-m2-bkey-usb3.dtbo
 dtb-$(CONFIG_ARCH_K3) += k3-am6528-iot2050-basic.dtb
 dtb-$(CONFIG_ARCH_K3) += k3-am6528-iot2050-basic-pg2.dtb
@@ -240,7 +242,10 @@ DTC_FLAGS_k3-am62p5-sk += -@
 DTC_FLAGS_k3-am642-evm += -@
 DTC_FLAGS_k3-am642-phyboard-electra-rdk += -@
 DTC_FLAGS_k3-am642-tqma64xxl-mbax4xxl += -@
+DTC_FLAGS_k3-am6548-iot2050-advanced += -@
 DTC_FLAGS_k3-am6548-iot2050-advanced-m2 += -@
+DTC_FLAGS_k3-am6548-iot2050-advanced-pg2 += -@
+DTC_FLAGS_k3-am6548-iot2050-advanced-sm += -@
 DTC_FLAGS_k3-am68-sk-base-board += -@
 DTC_FLAGS_k3-am69-sk += -@
 DTC_FLAGS_k3-j721e-common-proc-board += -@
diff --git a/arch/arm64/boot/dts/ti/k3-am6548-iot2050-advanced-dma-isolation.dtso b/arch/arm64/boot/dts/ti/k3-am6548-iot2050-advanced-dma-isolation.dtso
new file mode 100644
index 000000000000..dfd75d2dc245
--- /dev/null
+++ b/arch/arm64/boot/dts/ti/k3-am6548-iot2050-advanced-dma-isolation.dtso
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * IOT2050, overlay for isolating DMA requests via PVU
+ * Copyright (c) Siemens AG, 2024
+ *
+ * Authors:
+ *   Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
+ */
+
+/dts-v1/;
+/plugin/;
+
+&{/reserved-memory} {
+	#address-cells = <2>;
+	#size-cells = <2>;
+
+	pci_restricted_dma_region: restricted-dma@c0000000 {
+		compatible = "restricted-dma-pool";
+		reg = <0 0xc0000000 0 0x4000000>;
+	};
+};
+
+&pcie0_rc {
+	memory-region = <&pci_restricted_dma_region>;
+};
+
+&pcie1_rc {
+	memory-region = <&pci_restricted_dma_region>;
+};
+
+&ti_pvu0 {
+	status = "okay";
+};
-- 
2.43.0