iommu/riscv: Add RISC-V IOMMU platform device driver

Introduce platform device driver for implementation of RISC-V IOMMU
architected hardware.

Hardware interface definition located in file iommu-bits.h is based on
ratified RISC-V IOMMU Architecture Specification version 1.0.0.

This patch implements platform device initialization, early check and
configuration of the IOMMU interfaces and enables global pass-through
address translation mode (iommu_mode == BARE), without registering
hardware instance in the IOMMU subsystem.

Link: https://github.com/riscv-non-isa/riscv-iommu
Co-developed-by: Nick Kossifidis <mick@ics.forth.gr>
Signed-off-by: Nick Kossifidis <mick@ics.forth.gr>
Co-developed-by: Sebastien Boeuf <seb@rivosinc.com>
Signed-off-by: Sebastien Boeuf <seb@rivosinc.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Tomasz Jeznach <tjeznach@rivosinc.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Link: https://lore.kernel.org/r/2f2e4530c0ee4a81385efa90f1da932f5179f3fb.1729059707.git.tjeznach@rivosinc.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: tjeznach

MAINTAINERS

@@ -19895,7 +19895,9 @@ M:	Tomasz Jeznach <tjeznach@rivosinc.com>
 L:	iommu@lists.linux.dev
 L:	linux-riscv@lists.infradead.org
 S:	Maintained
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/iommu/linux.git
 F:	Documentation/devicetree/bindings/iommu/riscv,iommu.yaml
+F:	drivers/iommu/riscv/
 
 RISC-V MICROCHIP FPGA SUPPORT
 M:	Conor Dooley <conor.dooley@microchip.com>

drivers/iommu/Kconfig

@@ -195,6 +195,7 @@ config MSM_IOMMU
 source "drivers/iommu/amd/Kconfig"
 source "drivers/iommu/intel/Kconfig"
 source "drivers/iommu/iommufd/Kconfig"
+source "drivers/iommu/riscv/Kconfig"
 
 config IRQ_REMAP
 	bool "Support for Interrupt Remapping"

drivers/iommu/Makefile

@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
-obj-y += amd/ intel/ arm/ iommufd/
+obj-y += amd/ intel/ arm/ iommufd/ riscv/
 obj-$(CONFIG_IOMMU_API) += iommu.o
 obj-$(CONFIG_IOMMU_API) += iommu-traces.o
 obj-$(CONFIG_IOMMU_API) += iommu-sysfs.o

drivers/iommu/riscv/Kconfig

@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0-only
+# RISC-V IOMMU support
+
+config RISCV_IOMMU
+	bool "RISC-V IOMMU Support"
+	depends on RISCV && 64BIT
+	default y
+	select IOMMU_API
+	help
+	  Support for implementations of the RISC-V IOMMU architecture that
+	  complements the RISC-V MMU capabilities, providing similar address
+	  translation and protection functions for accesses from I/O devices.
+
+	  Say Y here if your SoC includes an IOMMU device implementing
+	  the RISC-V IOMMU architecture.

drivers/iommu/riscv/Makefile

@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_RISCV_IOMMU) += iommu.o iommu-platform.o