SMMU Software Detailed Design (SWE.3)

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1 Overview

The SMMU Software Detailed Design specifies the internal logic, data structures, and algorithms of the SMMUv3 driver components. It provides a blueprint for implementation (SWE.4) and ensures that each software unit is verifiable and traceable to the architectural design (SWE.2).

2 Component: SMMUv3 Core

2.1 Type Definition

| Type Name | Description | | :— | :— | | struct arm_smmu_device | Main data structure holding SMMU hardware state (features, queues, strtab). | | struct arm_smmu_cmdq_ent | Structure representing a single command queue entry (opcode + operands). |

2.2 Macro Definition

| Macro Name | Description | | :— | :— | | CMDQ_ERR_CERROR_NONE_IDX | Index for ‘no error’ in command queue error reporting. | | STRTAB_STE_0_CFG_BYPASS | Configuration value to set an STE to bypass translation. |

2.3 Global Variables

| Declaration | Type | Description | | :— | :— | :— | | arm_smmu_ops | struct iommu_ops | Function pointers for the generic IOMMU subsystem interface. |

2.4 Function Specification

2.4.1 arm_smmu_device_probe

SMMUv3 Device Initialization

• Property: Synchronous, Non-reentrant
• Description: Entry point for SMMUv3 initialization. Detects hardware features, allocates queues/tables, and registers the device.

Item	Description
Function Scope	Global (init)
Parameters	struct platform_device *pdev
Return	0 on success, negative error code on failure.

2.4.2 arm_smmu_map

Map IOVA to Physical Address

• Property: Synchronous, Reentrant
• Description: Maps a virtual address range to a physical address range in the page tables.

Item	Description
Function Scope	Internal (via ops)
Parameters	struct iommu_domain *domain, unsigned long iova, phys_addr_t paddr, size_t size, int prot
Return	0 on success, or error code.

3 Annex

3.1 Annex A. Evaluation Criteria for Detailed Software Design

The design is evaluated based on HIS metrics:

1. Complexity: Cyclomatic Complexity <= 10.
2. Coupling: Calling Functions <= 5, Called Functions <= 7.

4 Terms and Abbreviations

Terms and Abbreviations	Description
IOVA	Input Output Virtual Address
STE	Stream Table Entry

5 References

Documents Name	Version
SMMU Software Architectural Design (SWE.2)	1.0
Linux Kernel Source (drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c)	6.12