Re: [PATCH v13 06/10] iommu/arm-smmu-v3: Add acpi_smmu_acpi_probe_model for impl

[Robin Murphy]

On 27/08/2024 2:02 pm, Will Deacon wrote:
> On Fri, Aug 23, 2024 at 05:10:40PM -0700, Nicolin Chen wrote:
> > For model-specific implementation, repurpose the acpi_smmu_get_options()
> > to a wider acpi_smmu_acpi_probe_model(). A new model can add to the list
> > in this new function.
> >
> > Suggested-by: Will Deacon <will@xxxxxxxxxx>
> > Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> > ---
> >   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 18 +++++++++++++-----
> >   1 file changed, 13 insertions(+), 5 deletions(-)
> >
> > 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 afdb8a76a72a..ceb31d63f79b 100644
> > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > @@ -4341,18 +4341,28 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
> >   }
> >   
> >   #ifdef CONFIG_ACPI
> > -static void acpi_smmu_get_options(u32 model, struct arm_smmu_device *smmu)
> > +static int acpi_smmu_iort_probe_model(struct acpi_iort_node *node,
> > +				      struct arm_smmu_device *smmu)
> >   {
> > -	switch (model) {
> > +	struct acpi_iort_smmu_v3 *iort_smmu =
> > +		(struct acpi_iort_smmu_v3 *)node->node_data;
> > +
> > +	switch (iort_smmu->model) {
> >   	case ACPI_IORT_SMMU_V3_CAVIUM_CN99XX:
> >   		smmu->options |= ARM_SMMU_OPT_PAGE0_REGS_ONLY;
> >   		break;
> >   	case ACPI_IORT_SMMU_V3_HISILICON_HI161X:
> >   		smmu->options |= ARM_SMMU_OPT_SKIP_PREFETCH;
> >   		break;
> > +	case ACPI_IORT_SMMU_V3_GENERIC:
> > +		break;
> > +	default:
> > +		dev_err(smmu->dev, "Unknown/unsupported IORT model!\n");
> > +		return -ENXIO;
>
> We probably don't want this 'default' case, otherwise the driver will
> need to be updated every time there's a new model.

...although the intent is very strongly that there should never be any 
new models, because by now hardware should really not be failing to 
implement SMMU_IIDR correctly. In some ways, having this might help 
further discourage people from abusing the mechanism and making random 
stuff up in their firmware :/

Cheers,
Robin.