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

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Message-ID: <5e9a0ce1-a0ba-4a31-be95-99f349ec6028@nvidia.com>
Date: Thu, 18 Dec 2025 12:02:25 +0530
From: Ashish Mhetre <amhetre@...dia.com>
To: Jon Hunter <jonathanh@...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 12/18/2025 2:13 AM, Jon Hunter wrote:
>
>
> 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?
>

This info print is similar to what is there in ACPI path as well.
It's only a single print per SMMU at boot time. Should I still change
it to 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;
>>   }
>