Re: [PATCH V6 1/4] iommu/tegra241-cmdqv: Decouple driver from ACPI

[Robin Murphy]

On 12/12/2025 7:46 pm, Nicolin Chen wrote:
> On Fri, Dec 12, 2025 at 12:01:41PM +0000, Robin Murphy wrote:
> > > @@ -4542,7 +4542,7 @@ static void acpi_smmu_dsdt_probe_tegra241_cmdqv(struct acpi_iort_node *node,
> > >    	adev = acpi_dev_get_first_match_dev("NVDA200C", uid, -1);
> > >    	if (adev) {
> > >    		/* Tegra241 CMDQV driver is responsible for put_device() */
> >
> > Don't we need to bring the put_device(adev) out to this level, since
> > impl_dev is now something else that AFAICS we are *not* taking a new
> > reference on (and thus should not be putting either)?
>
> Ah, right! We are using the platform device now.
>
> > > -		smmu->impl_dev = &adev->dev;
> > > +		smmu->impl_dev = acpi_get_first_physical_node(adev);
> > >    		smmu->options |= ARM_SMMU_OPT_TEGRA241_CMDQV;
> > >    		dev_info(smmu->dev, "found companion CMDQV device: %s\n",
> > >    			 dev_name(smmu->impl_dev));
>
> I think we should squash this:

Ack, it occurred to me shortly after sending that in fact it's good to 
still hold our own reference on impl_dev itself, as we're not relying on 
a bound driver to hold one for us.

Cheers,
Robin.

> 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 0c98be3135c63..88625e3c27a65 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -5280,10 +5280,11 @@ static void acpi_smmu_dsdt_probe_tegra241_cmdqv(struct acpi_iort_node *node,
>   	adev = acpi_dev_get_first_match_dev("NVDA200C", uid, -1);
>   	if (adev) {
>   		/* Tegra241 CMDQV driver is responsible for put_device() */
> -		smmu->impl_dev = acpi_get_first_physical_node(adev);
> +		smmu->impl_dev = get_device(acpi_get_first_physical_node(adev));
>   		smmu->options |= ARM_SMMU_OPT_TEGRA241_CMDQV;
>   		dev_info(smmu->dev, "found companion CMDQV device: %s\n",
>   			 dev_name(smmu->impl_dev));
> +		acpi_dev_put(adev);
>   	}
>   	kfree(uid);
>   }
>
> Thanks
> Nicolin