[PATCH v6 3/3] iommu/riscv: Add ACPI support

Sunil V L
2025-08-18T05:32:30Z

RISC-V IO Mapping Table (RIMT) provides the information about the IOMMU
to the OS in ACPI. Add support for ACPI in RISC-V IOMMU drivers by using
RIMT data.

The changes at high level are,

a) Register the IOMMU with RIMT data structures.
b) Enable probing of platform IOMMU in ACPI way using the ACPIID defined
for the RISC-V IOMMU in the BRS spec [1]. Configure the MSI domain if
the platform IOMMU uses MSIs.

[1] - https://github.com/riscv-non-isa/riscv-brs/blob/main/acpi-id.adoc

Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Acked-by: Will Deacon <will@kernel.org>
---
drivers/iommu/riscv/iommu-platform.c | 17 ++++++++++++++++-
drivers/iommu/riscv/iommu.c | 10 ++++++++++
2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/riscv/iommu-platform.c b/drivers/iommu/riscv/iommu-platform.c
index 725e919b97ef..83a28c83f991 100644
--- a/drivers/iommu/riscv/iommu-platform.c
+++ b/drivers/iommu/riscv/iommu-platform.c
@@ -10,6 +10,8 @@
* Tomasz Jeznach <tjeznach@rivosinc.com>
*/

+#include <linux/acpi.h>
+#include <linux/irqchip/riscv-imsic.h>
#include <linux/kernel.h>
#include <linux/msi.h>
#include <linux/of_irq.h>
@@ -46,6 +48,7 @@ static int riscv_iommu_platform_probe(struct platform_device *pdev)
enum riscv_iommu_igs_settings igs;
struct device *dev = &pdev->dev;
struct riscv_iommu_device *iommu = NULL;
+ struct irq_domain *msi_domain;
struct resource *res = NULL;
int vec, ret;

@@ -76,8 +79,13 @@ static int riscv_iommu_platform_probe(struct platform_device *pdev)
switch (igs) {
case RISCV_IOMMU_CAPABILITIES_IGS_BOTH:
case RISCV_IOMMU_CAPABILITIES_IGS_MSI:
- if (is_of_node(dev->fwnode))
+ if (is_of_node(dev_fwnode(dev))) {
of_msi_configure(dev, to_of_node(dev->fwnode));
+ } else {
+ msi_domain = irq_find_matching_fwnode(imsic_acpi_get_fwnode(dev),
+ DOMAIN_BUS_PLATFORM_MSI);
+ dev_set_msi_domain(dev, msi_domain);
+ }

if (!dev_get_msi_domain(dev)) {
dev_warn(dev, "failed to find an MSI domain\n");
@@ -150,6 +158,12 @@ static const struct of_device_id riscv_iommu_of_match[] = {
{},
};

+static const struct acpi_device_id riscv_iommu_acpi_match[] = {
+ { "RSCV0004", 0 },
+ {}
+};
+MODULE_DEVICE_TABLE(acpi, riscv_iommu_acpi_match);
+
static struct platform_driver riscv_iommu_platform_driver = {
.probe = riscv_iommu_platform_probe,
.remove = riscv_iommu_platform_remove,
@@ -158,6 +172,7 @@ static struct platform_driver riscv_iommu_platform_driver = {
.name = "riscv,iommu",
.of_match_table = riscv_iommu_of_match,
.suppress_bind_attrs = true,
+ .acpi_match_table = riscv_iommu_acpi_match,
},
};

diff --git a/drivers/iommu/riscv/iommu.c b/drivers/iommu/riscv/iommu.c
index 2d0d31ba2886..7d9370aa58f0 100644
--- a/drivers/iommu/riscv/iommu.c
+++ b/drivers/iommu/riscv/iommu.c
@@ -12,6 +12,8 @@

#define pr_fmt(fmt) "riscv-iommu: " fmt

+#include <linux/acpi.h>
+#include <linux/acpi_rimt.h>
#include <linux/compiler.h>
#include <linux/crash_dump.h>
#include <linux/init.h>
@@ -1650,6 +1652,14 @@ int riscv_iommu_init(struct riscv_iommu_device *iommu)
goto err_iodir_off;
}

+ if (!acpi_disabled) {
+ rc = rimt_iommu_register(iommu->dev);
+ if (rc) {
+ dev_err_probe(iommu->dev, rc, "cannot register iommu with RIMT\n");
+ goto err_remove_sysfs;
+ }
+ }
+
rc = iommu_device_register(&iommu->iommu, &riscv_iommu_ops, iommu->dev);
if (rc) {
dev_err_probe(iommu->dev, rc, "cannot register iommu interface\n");