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

[Ashish Mhetre]

On 12/13/2025 2:06 AM, Robin Murphy wrote:
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>
>
> 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.

Ack, thanks Nic and Robin. I will include this and send
new version.

> > 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