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

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Message-ID: <e7d3e95f-a885-4b13-ab4d-bc82793c5396@nvidia.com>
Date: Thu, 18 Dec 2025 08:48:32 +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 18/12/2025 06:32, Ashish Mhetre wrote:
> 
> 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?

Yes, I would.

Jon

-- 
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