ACPI: RISC-V: Add support for RIMT

RISC-V IO Mapping Table (RIMT) is a static ACPI table to communicate
IOMMU information to the OS. The spec is available at [1].

The changes at high level are,
	a) Initialize data structures required for IOMMU/device
	   configuration using the data from RIMT. Provide APIs required
	   for device configuration.
	b) Provide an API for IOMMU drivers to register the
	   fwnode with RIMT data structures. This API will create a
	   fwnode for PCIe IOMMU.

[1] - https://github.com/riscv-non-isa/riscv-acpi-rimt

Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20250818045807.763922-2-sunilvl@ventanamicro.com
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

MAINTAINERS

@@ -347,6 +347,7 @@ L:	linux-acpi@vger.kernel.org
 L:	linux-riscv@lists.infradead.org
 S:	Maintained
 F:	drivers/acpi/riscv/
+F:	include/linux/acpi_rimt.h
 
 ACPI PCC(Platform Communication Channel) MAILBOX DRIVER
 M:	Sudeep Holla <sudeep.holla@arm.com>

arch/riscv/Kconfig

@@ -16,6 +16,7 @@ config RISCV
 	select ACPI_MCFG if (ACPI && PCI)
 	select ACPI_PPTT if ACPI
 	select ACPI_REDUCED_HARDWARE_ONLY if ACPI
+	select ACPI_RIMT if ACPI
 	select ACPI_SPCR_TABLE if ACPI
 	select ARCH_DMA_DEFAULT_COHERENT
 	select ARCH_ENABLE_HUGEPAGE_MIGRATION if HUGETLB_PAGE && MIGRATION

drivers/acpi/Kconfig

@@ -547,6 +547,10 @@ if ARM64
 source "drivers/acpi/arm64/Kconfig"
 endif
 
+if RISCV
+source "drivers/acpi/riscv/Kconfig"
+endif
+
 config ACPI_PPTT
 	bool
 

drivers/acpi/riscv/Kconfig

@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# ACPI Configuration for RISC-V
+#
+
+config ACPI_RIMT
+	bool

drivers/acpi/riscv/Makefile

@@ -2,3 +2,4 @@
 obj-y					+= rhct.o init.o irq.o
 obj-$(CONFIG_ACPI_PROCESSOR_IDLE)	+= cpuidle.o
 obj-$(CONFIG_ACPI_CPPC_LIB)		+= cppc.o
+obj-$(CONFIG_ACPI_RIMT)			+= rimt.o

drivers/acpi/riscv/init.c

@@ -10,4 +10,6 @@
 void __init acpi_arch_init(void)
 {
 	riscv_acpi_init_gsi_mapping();
+	if (IS_ENABLED(CONFIG_ACPI_RIMT))
+		riscv_acpi_rimt_init();
 }

drivers/acpi/riscv/init.h

@@ -2,3 +2,4 @@
 #include <linux/init.h>
 
 void __init riscv_acpi_init_gsi_mapping(void);
+void __init riscv_acpi_rimt_init(void);

include/linux/acpi_rimt.h

@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ *  Copyright (C) 2024-2025, Ventana Micro Systems Inc.
+ *	Author: Sunil V L <sunilvl@ventanamicro.com>
+ */
+
+#ifndef _ACPI_RIMT_H
+#define _ACPI_RIMT_H
+
+#ifdef CONFIG_ACPI_RIMT
+int rimt_iommu_register(struct device *dev);
+#else
+static inline int rimt_iommu_register(struct device *dev)
+{
+	return -ENODEV;
+}
+#endif
+
+#if defined(CONFIG_IOMMU_API) && defined(CONFIG_ACPI_RIMT)
+int rimt_iommu_configure_id(struct device *dev, const u32 *id_in);
+#else
+static inline int rimt_iommu_configure_id(struct device *dev, const u32 *id_in)
+{
+	return -ENODEV;
+}
+#endif
+
+#endif /* _ACPI_RIMT_H */