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

From: Robin Murphy
Date: Tue Aug 27 2024 - 11:58:08 EST


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.