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Message-ID: <42dfb0ed-33ef-4fb3-90be-82be77f3f642@nvidia.com>
Date: Mon, 1 Dec 2025 21:25:08 +0530
From: Ashish Mhetre <amhetre@...dia.com>
To: Robin Murphy <robin.murphy@....com>, will@...nel.org, joro@...tes.org,
robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org, nicolinc@...dia.com
Cc: thierry.reding@...il.com, jonathanh@...dia.com, vdumpa@...dia.com,
jgg@...pe.ca, linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-tegra@...r.kernel.org
Subject: Re: [PATCH V2 1/3] iommu/arm-smmu-v3: Add device-tree support for
CMDQV driver
On 11/25/2025 10:55 PM, Robin Murphy wrote:
> External email: Use caution opening links or attachments
>
>
> On 2025-11-25 7:16 am, Ashish Mhetre wrote:
>> Add device tree support to the CMDQV driver to enable usage on Tegra264
>> SoCs. The implementation parses the nvidia,cmdqv phandle from the SMMU
>> device tree node to associate each SMMU with its corresponding CMDQV
>> instance.
>>
>> Update the dependency from Kconfig as the driver now supports both
>> ACPI and device tree initialization through conditional compilation.
>>
>> Add nvidia,tegra264-smmu to the arm-smmu-v3 device tree match table to
>> enable device tree based probing on Nvidia Tegra264 platforms and
>> restrict CMDQV usage to other vendors.
>>
>> Reviewed-by: Nicolin Chen <nicolinc@...dia.com>
>> Signed-off-by: Ashish Mhetre <amhetre@...dia.com>
>> ---
>> drivers/iommu/arm/Kconfig | 2 +-
>> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 32 ++++++++++++++
>> .../iommu/arm/arm-smmu-v3/tegra241-cmdqv.c | 43 ++++++++++++++++++-
>> 3 files changed, 75 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/iommu/arm/Kconfig b/drivers/iommu/arm/Kconfig
>> index ef42bbe07dbe..168ada9c3d68 100644
>> --- a/drivers/iommu/arm/Kconfig
>> +++ b/drivers/iommu/arm/Kconfig
>> @@ -121,7 +121,7 @@ config ARM_SMMU_V3_KUNIT_TEST
>>
>> config TEGRA241_CMDQV
>> bool "NVIDIA Tegra241 CMDQ-V extension support for ARM SMMUv3"
>> - depends on ACPI
>> + depends on OF || ACPI
>
> This now does nothing, since ARM_SMMU_V3 depends on ARM64 which already
> implies at least OF anyway.
>
Acknowledged, I will remove the dependency.
>> 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 a33fbd12a0dd..2eec7cd4f3de 100644
>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> @@ -4530,6 +4530,34 @@ static int arm_smmu_device_hw_probe(struct
>> arm_smmu_device *smmu)
>> return 0;
>> }
>>
>> +#ifdef CONFIG_TEGRA241_CMDQV
>> +static void tegra_cmdqv_dt_probe(struct device_node *smmu_node,
>> + struct arm_smmu_device *smmu)
>> +{
>> + struct platform_device *pdev;
>> + struct device_node *np;
>> +
>> + np = of_parse_phandle(smmu_node, "nvidia,cmdqv", 0);
>> + if (!np)
>> + return;
>> +
>> + pdev = of_find_device_by_node(np);
>> + of_node_put(np);
>> + if (!pdev)
>> + return;
>> +
>
> You need to drop the reference on the platform device too.
>
Yes, I will fix this in next revision.
>> + smmu->impl_dev = &pdev->dev;
>> + smmu->options |= ARM_SMMU_OPT_TEGRA241_CMDQV;
>> + dev_info(smmu->dev, "found companion CMDQV device: %s\n",
>> + dev_name(smmu->impl_dev));
>> +}
>> +#else
>> +static void tegra_cmdqv_dt_probe(struct device_node *smmu_node,
>> + struct arm_smmu_device *smmu)
>> +{
>> +}
>> +#endif
>> +
>> #ifdef CONFIG_ACPI
>> #ifdef CONFIG_TEGRA241_CMDQV
>> static void acpi_smmu_dsdt_probe_tegra241_cmdqv(struct
>> acpi_iort_node *node,
>> @@ -4634,6 +4662,9 @@ static int arm_smmu_device_dt_probe(struct
>> platform_device *pdev,
>> if (of_dma_is_coherent(dev->of_node))
>> smmu->features |= ARM_SMMU_FEAT_COHERENCY;
>>
>> + if (of_device_is_compatible(dev->of_node, "nvidia,tegra264-smmu"))
>> + tegra_cmdqv_dt_probe(dev->of_node, smmu);
>> +
>> return ret;
>> }
>>
>> @@ -4867,6 +4898,7 @@ static void arm_smmu_device_shutdown(struct
>> platform_device *pdev)
>>
>> static const struct of_device_id arm_smmu_of_match[] = {
>> { .compatible = "arm,smmu-v3", },
>> + { .compatible = "nvidia,tegra264-smmu", },
>
> Since you're not using match data, this is pointless, as anything with
> this compatible must still also match the generic compatible anyway.
>
Sure, I'll remove "nvidia,tegra264-smmu" in next version.
> Thanks,
> Robin.
>
>> { },
>> };
>> MODULE_DEVICE_TABLE(of, arm_smmu_of_match);
>> diff --git a/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
>> b/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
>> index 378104cd395e..2608bf6518b4 100644
>> --- a/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
>> +++ b/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
>> @@ -11,6 +11,8 @@
>> #include <linux/iommufd.h>
>> #include <linux/iopoll.h>
>> #include <uapi/linux/iommufd.h>
>> +#include <linux/of_platform.h>
>> +#include <linux/platform_device.h>
>>
>> #include <acpi/acpixf.h>
>>
>> @@ -917,6 +919,26 @@ tegra241_cmdqv_find_acpi_resource(struct device
>> *dev, int *irq)
>> return res;
>> }
>>
>> +static struct resource *
>> +tegra241_cmdqv_find_dt_resource(struct device *dev, int *irq)
>> +{
>> + struct platform_device *pdev = to_platform_device(dev);
>> + struct resource *res;
>> +
>> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> + if (!res) {
>> + dev_err(dev, "no memory resource found for CMDQV\n");
>> + return NULL;
>> + }
>> +
>> + if (irq)
>> + *irq = platform_get_irq_optional(pdev, 0);
>> + if (!irq || *irq <= 0)
>> + dev_warn(dev, "no interrupt. errors will not be
>> reported\n");
>> +
>> + return res;
>> +}
>> +
>> static int tegra241_cmdqv_init_structures(struct arm_smmu_device
>> *smmu)
>> {
>> struct tegra241_cmdqv *cmdqv =
>> @@ -1048,11 +1070,14 @@ struct arm_smmu_device
>> *tegra241_cmdqv_probe(struct arm_smmu_device *smmu)
>>
>> if (!smmu->dev->of_node)
>> res = tegra241_cmdqv_find_acpi_resource(smmu->impl_dev,
>> &irq);
>> + else
>> + res = tegra241_cmdqv_find_dt_resource(smmu->impl_dev,
>> &irq);
>> if (!res)
>> goto out_fallback;
>>
>> new_smmu = __tegra241_cmdqv_probe(smmu, res, irq);
>> - kfree(res);
>> + if (!smmu->dev->of_node)
>> + kfree(res);
>>
>> if (new_smmu)
>> return new_smmu;
>> @@ -1346,4 +1371,20 @@ tegra241_cmdqv_init_vintf_user(struct
>> arm_vsmmu *vsmmu,
>> return ret;
>> }
>>
>> +static const struct of_device_id tegra241_cmdqv_of_match[] = {
>> + { .compatible = "nvidia,tegra264-cmdqv" },
>> + { /* sentinel */ }
>> +};
>> +MODULE_DEVICE_TABLE(of, tegra241_cmdqv_of_match);
>> +
>> +static struct platform_driver tegra241_cmdqv_driver = {
>> + .driver = {
>> + .name = "tegra241-cmdqv",
>> + .of_match_table = tegra241_cmdqv_of_match,
>> + },
>> +};
>> +module_platform_driver(tegra241_cmdqv_driver);
>> +
>> +MODULE_DESCRIPTION("NVIDIA Tegra241 Command Queue Virtualization
>> Driver");
>> +MODULE_LICENSE("GPL");
>> MODULE_IMPORT_NS("IOMMUFD");
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