Re: [PATCH V4 1/3] iommu/arm-smmu-v3: Add device-tree support for CMDQV driver

[Nicolin Chen <nicolinc@nvidia.com>]

On Wed, Dec 10, 2025 at 12:39:49PM +0000, Robin Murphy wrote:
> On 2025-12-10 5:19 am, Ashish Mhetre wrote:
> [...]
> > Hi Robin, Nic,
> > We removed ACPI dependency in Kconfig but driver still depends
> > on ACPI for these functions. I will be protecting ACPIspecific
> > tegra241-cmdqv code under CONFIG_ACPI similar to what is done
> > in arm-smmu-v3 driver. Is this the correct thing to do or do you
> > have any other suggestions?
> 
> Yes, when I commented that "depends on ACPI || OF" was functionally the same
> as just removing "depends on ACPI", I didn't mean to suggest that wasn't
> necessarily a genuine dependency still.
> 
> I guess if you can wrap the ACPI-specific functions in a single #ifdef block
> that's reasonable, however I do now wonder whether things couldn't be
> factored out a bit more - if it's a standard DSDT/SSDT namespace device,
> shouldn't there also be a corresponding platform device created for it,
> which we could look up instead of delving directly into the _CRS of the ACPI
> node itself? (not sure off-hand if there's a straightforward inverse of
> ACPI_COMPANION()...)

Ah, I did a quick tracer at acpi_create_platform_device(). And I
do see platform devices being created. So, we could have made it
ACPI-independent from the beginning, as you expected :)

Ashish, let's attach the following patch in your series:

From 7b69a638276e66b16b923b0ce1743d3efc85a04c Mon Sep 17 00:00:00 2001
From: Nicolin Chen <nicolinc@nvidia.com>
Date: Thu, 11 Dec 2025 05:47:05 +0000
Subject: [PATCH] iommu/tegra241-cmdqv: Decouple driver from ACPI

A platform device is created by acpi_create_platform_device() per CMDQV's
adev. That means there is no point in going through _CRS of ACPI.

Replace all the ACPI functions with standard platform functions. And drop
all ACPI dependencies. This will make the driver compatible with DT also.

Suggested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
 drivers/iommu/arm/Kconfig                     |  1 -
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c   |  2 +-
 .../iommu/arm/arm-smmu-v3/tegra241-cmdqv.c    | 84 +++----------------
 3 files changed, 13 insertions(+), 74 deletions(-)

diff --git a/drivers/iommu/arm/Kconfig b/drivers/iommu/arm/Kconfig
index ef42bbe07dbef..5fac08b89deea 100644
--- a/drivers/iommu/arm/Kconfig
+++ b/drivers/iommu/arm/Kconfig
@@ -121,7 +121,6 @@ config ARM_SMMU_V3_KUNIT_TEST
 
 config TEGRA241_CMDQV
 	bool "NVIDIA Tegra241 CMDQ-V extension support for ARM SMMUv3"
-	depends on ACPI
 	help
 	  Support for NVIDIA CMDQ-Virtualization extension for ARM SMMUv3. The
 	  CMDQ-V extension is similar to v3.3 ECMDQ for multi command queues
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 38028e4a52f7f..0c98be3135c63 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -5280,7 +5280,7 @@ static void acpi_smmu_dsdt_probe_tegra241_cmdqv(struct acpi_iort_node *node,
 	adev = acpi_dev_get_first_match_dev("NVDA200C", uid, -1);
 	if (adev) {
 		/* Tegra241 CMDQV driver is responsible for put_device() */
-		smmu->impl_dev = &adev->dev;
+		smmu->impl_dev = acpi_get_first_physical_node(adev);
 		smmu->options |= ARM_SMMU_OPT_TEGRA241_CMDQV;
 		dev_info(smmu->dev, "found companion CMDQV device: %s\n",
 			 dev_name(smmu->impl_dev));
diff --git a/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c b/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
index 378104cd395e5..1fc03b72beb88 100644
--- a/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
+++ b/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
@@ -3,17 +3,15 @@
 
 #define dev_fmt(fmt) "tegra241_cmdqv: " fmt
 
-#include <linux/acpi.h>
 #include <linux/debugfs.h>
 #include <linux/dma-mapping.h>
 #include <linux/interrupt.h>
 #include <linux/iommu.h>
 #include <linux/iommufd.h>
 #include <linux/iopoll.h>
+#include <linux/platform_device.h>
 #include <uapi/linux/iommufd.h>
 
-#include <acpi/acpixf.h>
-
 #include "arm-smmu-v3.h"
 
 /* CMDQV register page base and size defines */
@@ -854,69 +852,6 @@ static struct arm_smmu_impl_ops tegra241_cmdqv_impl_ops = {
 
 /* Probe Functions */
 
-static int tegra241_cmdqv_acpi_is_memory(struct acpi_resource *res, void *data)
-{
-	struct resource_win win;
-
-	return !acpi_dev_resource_address_space(res, &win);
-}
-
-static int tegra241_cmdqv_acpi_get_irqs(struct acpi_resource *ares, void *data)
-{
-	struct resource r;
-	int *irq = data;
-
-	if (*irq <= 0 && acpi_dev_resource_interrupt(ares, 0, &r))
-		*irq = r.start;
-	return 1; /* No need to add resource to the list */
-}
-
-static struct resource *
-tegra241_cmdqv_find_acpi_resource(struct device *dev, int *irq)
-{
-	struct acpi_device *adev = to_acpi_device(dev);
-	struct list_head resource_list;
-	struct resource_entry *rentry;
-	struct resource *res = NULL;
-	int ret;
-
-	INIT_LIST_HEAD(&resource_list);
-	ret = acpi_dev_get_resources(adev, &resource_list,
-				     tegra241_cmdqv_acpi_is_memory, NULL);
-	if (ret < 0) {
-		dev_err(dev, "failed to get memory resource: %d\n", ret);
-		return NULL;
-	}
-
-	rentry = list_first_entry_or_null(&resource_list,
-					  struct resource_entry, node);
-	if (!rentry) {
-		dev_err(dev, "failed to get memory resource entry\n");
-		goto free_list;
-	}
-
-	/* Caller must free the res */
-	res = kzalloc(sizeof(*res), GFP_KERNEL);
-	if (!res)
-		goto free_list;
-
-	*res = *rentry->res;
-
-	acpi_dev_free_resource_list(&resource_list);
-
-	INIT_LIST_HEAD(&resource_list);
-
-	if (irq)
-		ret = acpi_dev_get_resources(adev, &resource_list,
-					     tegra241_cmdqv_acpi_get_irqs, irq);
-	if (ret < 0 || !irq || *irq <= 0)
-		dev_warn(dev, "no interrupt. errors will not be reported\n");
-
-free_list:
-	acpi_dev_free_resource_list(&resource_list);
-	return res;
-}
-
 static int tegra241_cmdqv_init_structures(struct arm_smmu_device *smmu)
 {
 	struct tegra241_cmdqv *cmdqv =
@@ -1042,18 +977,23 @@ __tegra241_cmdqv_probe(struct arm_smmu_device *smmu, struct resource *res,
 
 struct arm_smmu_device *tegra241_cmdqv_probe(struct arm_smmu_device *smmu)
 {
+	struct platform_device *pdev = to_platform_device(smmu->impl_dev);
 	struct arm_smmu_device *new_smmu;
-	struct resource *res = NULL;
+	struct resource *res;
 	int irq;
 
-	if (!smmu->dev->of_node)
-		res = tegra241_cmdqv_find_acpi_resource(smmu->impl_dev, &irq);
-	if (!res)
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		dev_err(&pdev->dev, "no memory resource found for CMDQV\n");
 		goto out_fallback;
+	}
 
-	new_smmu = __tegra241_cmdqv_probe(smmu, res, irq);
-	kfree(res);
+	irq = platform_get_irq_optional(pdev, 0);
+	if (irq <= 0)
+		dev_warn(&pdev->dev,
+			 "no interrupt. errors will not be reported\n");
 
+	new_smmu = __tegra241_cmdqv_probe(smmu, res, irq);
 	if (new_smmu)
 		return new_smmu;
 
-- 
2.43.0