linux-kernel - Re: [PATCH V7 2/4] iommu/arm-smmu-v3: Add device-tree support for CMDQV driver

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Message-ID: <23df682e-6d08-4827-994e-1bbd89e5c903@nvidia.com>
Date: Wed, 17 Dec 2025 20:43:08 +0000
From: Jon Hunter <jonathanh@...dia.com>
To: Ashish Mhetre <amhetre@...dia.com>, will@...nel.org,
 robin.murphy@....com, joro@...tes.org, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, nicolinc@...dia.com
Cc: thierry.reding@...il.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 V7 2/4] iommu/arm-smmu-v3: Add device-tree support for
 CMDQV driver



On 15/12/2025 06:48, 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 based on compatible string.
> 
> Reviewed-by: Nicolin Chen <nicolinc@...dia.com>
> Signed-off-by: Ashish Mhetre <amhetre@...dia.com>
> ---
>   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 32 +++++++++++++++++++++
>   1 file changed, 32 insertions(+)
> 
> 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 dad3c0cb800b..0cd0013200f3 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 +4530,35 @@ 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;
> +
> +	/* Tegra241 CMDQV driver is responsible for put_device() */
> +	pdev = of_find_device_by_node(np);
> +	of_node_put(np);
> +	if (!pdev)
> +		return;
> +
> +	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));

This seems a bit noisy. dev_dbg?

> +}
> +#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,
> @@ -4635,6 +4664,9 @@ 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;
>   }
>   

-- 
nvpublic