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>
---
 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 bb57092ca901..45a263c9e0d5 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>
@@ -1651,6 +1653,14 @@ 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");
-- 
2.43.0

On Mon, Jun 30, 2025 at 09:18:03AM +0530, Sunil V L wrote:
> 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>
> ---
>  drivers/iommu/riscv/iommu-platform.c | 17 ++++++++++++++++-
>  drivers/iommu/riscv/iommu.c          | 10 ++++++++++
>  2 files changed, 26 insertions(+), 1 deletion(-)

This looks relatively straightforward from the IOMMU perspective
(assuming the driver still compiles if CONFIG_ACPI=n) but the ACPI parts
in the first two patches need reviewing before this can land.

Will

On Mon, Jun 30, 2025 at 09:18:03AM +0530, Sunil V L wrote:
> 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>
> ---
>  drivers/iommu/riscv/iommu-platform.c | 17 ++++++++++++++++-
>  drivers/iommu/riscv/iommu.c          | 10 ++++++++++
>  2 files changed, 26 insertions(+), 1 deletion(-)
>

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>