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

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Message-ID: <69e11fa5-558f-4fbd-ab3e-e8f3b8197df6@nvidia.com>
Date: Wed, 7 Jan 2026 12:14:31 +0530
From: Ashish Mhetre <amhetre@...dia.com>
To: Nicolin Chen <nicolinc@...dia.com>, Jon Hunter <jonathanh@...dia.com>
Cc: will@...nel.org, robin.murphy@....com, joro@...tes.org, robh@...nel.org,
 krzk+dt@...nel.org, conor+dt@...nel.org, 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 12/20/2025 12:19 AM, Nicolin Chen wrote:
> On Fri, Dec 19, 2025 at 10:48:22AM +0000, Jon Hunter wrote:
>> On 18/12/2025 18:57, Nicolin Chen wrote:
>>> On Thu, Dec 18, 2025 at 08:48:32AM +0000, Jon Hunter wrote:
>>>> On 18/12/2025 06:32, Ashish Mhetre wrote:
>>>>> On 12/18/2025 2:13 AM, Jon Hunter wrote:
>>>>>>> +    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.
>>> It's really not that bad IMHO, I am not against that though..
>>>
>>> If we have to change that, we'd need another patch changing the
>>> one in the ACPI path as well to keep things aligned.
>> Regardless of what is already present, does not mean we need add more prints
>> to just say everything is OK.
> This is how it looks like for each instance probe():
>
> [    2.709269] arm-smmu-v3 arm-smmu-v3.10.auto: found companion CMDQV device: NVDA200C:00
> [    2.709273] arm-smmu-v3 arm-smmu-v3.10.auto: option mask 0x10
> [    2.709618] arm-smmu-v3 arm-smmu-v3.10.auto: ias 48-bit, oas 48-bit (features 0x001e1fbf)
> [    2.716236] arm-smmu-v3 arm-smmu-v3.10.auto: allocated 524288 entries for cmdq
> [    2.719432] arm-smmu-v3 arm-smmu-v3.10.auto: allocated 524288 entries for evtq
> [    2.725898] arm-smmu-v3 arm-smmu-v3.10.auto: allocated 524288 entries for priq
> [    2.736051] arm-smmu-v3 arm-smmu-v3.10.auto: allocated 524288 entries for vcmdq0
> [    2.742553] arm-smmu-v3 arm-smmu-v3.10.auto: allocated 524288 entries for vcmdq1
> [    2.742586] arm-smmu-v3 arm-smmu-v3.10.auto: msi_domain absent - falling back to wired irqs
> [    2.742759] arm-smmu-v3 arm-smmu-v3.10.auto: no priq irq - PRI will be broken
>
> On a second thought: The CMDQV device has a very unclear naming in
> ACPI path: "NVDA200C:00". So, printing it gives us a hint for any
> later warning/error tagged with "NVDA200C:00".
>
> Now, for DT, it might be okay to not print it. But making the two
> paths asymmetric feels odd. So, is it really worth nitpicking here
> given that each SMMU already prints quite a few lines on probe()?
>
> Nicolin

Hi Jon, Nic,

Shall I keep this print or send a new version removing it?

Thanks,
Ashish Mhetre