smmu学习笔记之streamtable

2019-11-06 09:45:50

字体：大中小

来源：转载

供稿：网友

streamtable有两种组织方式，根据ARM_SMMU_FEAT_2_LVL_STRTAB来判断而这个flag是在arm_smmu_device_hw_PRobe 中通过读取ARM_SMMU_IDR0 这个寄存器来判断的static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu){ u32 reg; bool coherent = smmu->features & ARM_SMMU_FEAT_COHERENCY; /* IDR0 */ reg = readl_relaxed(smmu->base + ARM_SMMU_IDR0); /* 2-level structures */ if ((reg & IDR0_ST_LVL_MASK << IDR0_ST_LVL_SHIFT) == IDR0_ST_LVL_2LVL) smmu->features |= ARM_SMMU_FEAT_2_LVL_STRTAB;}所以在arm_smmu_init_strtab 中就根据这个flag 将streamtable分成两种组织方式static int arm_smmu_init_strtab(struct arm_smmu_device *smmu){ u64 reg; int ret; if (smmu->features & ARM_SMMU_FEAT_2_LVL_STRTAB) ret = arm_smmu_init_strtab_2lvl(smmu); else ret = arm_smmu_init_strtab_linear(smmu); if (ret) return ret; /* Set the strtab base address */ reg = smmu->strtab_cfg.strtab_dma & STRTAB_BASE_ADDR_MASK << STRTAB_BASE_ADDR_SHIFT; reg |= STRTAB_BASE_RA; smmu->strtab_cfg.strtab_base = reg; /* Allocate the first VMID for stage-2 bypass STEs */ set_bit(0, smmu->vmid_map); return 0;}不管采用哪种streamtable，都会对smmu->strtab_cfg.strtab_dma赋值，最后将smmu->strtab_cfg.strtab_dma 保存到smmu->strtab_cfg.strtab_base 中。我们先来看arm_smmu_init_strtab_2lvlstatic int arm_smmu_init_strtab_2lvl(struct arm_smmu_device *smmu){ void *strtab; u64 reg; u32 size, l1size;//让cfg 指针指向smmu->strtab_cfg struct arm_smmu_strtab_cfg *cfg = &smmu->strtab_cfg; /* * If we can resolve everything with a single L2 table, then we * just need a single L1 descriptor. Otherwise, calculate the L1 * size, capped to the SIDSIZE. */ if (smmu->sid_bits < STRTAB_SPLIT) { size = 0; } else { size = STRTAB_L1_SZ_SHIFT - (ilog2(STRTAB_L1_DESC_DWordS) + 3); size = min(size, smmu->sid_bits - STRTAB_SPLIT); }#计算l1 entry 的size cfg->num_l1_ents = 1 << size; size += STRTAB_SPLIT; if (size < smmu->sid_bits) dev_warn(smmu->dev, "2-level strtab only covers %u/%u bits of SID/n", size, smmu->sid_bits); l1size = cfg->num_l1_ents * (STRTAB_L1_DESC_DWORDS << 3);#为strtab 申请memory strtab = dmam_alloc_coherent(smmu->dev, l1size, &cfg->strtab_dma, GFP_KERNEL | __GFP_ZERO); if (!strtab) { dev_err(smmu->dev, "failed to allocate l1 stream table (%u bytes)/n", size); return -ENOMEM; } cfg->strtab = strtab; /* Configure strtab_base_cfg for 2 levels */ reg = STRTAB_BASE_CFG_FMT_2LVL; reg |= (size & STRTAB_BASE_CFG_LOG2SIZE_MASK) << STRTAB_BASE_CFG_LOG2SIZE_SHIFT; reg |= (STRTAB_SPLIT & STRTAB_BASE_CFG_SPLIT_MASK) << STRTAB_BASE_CFG_SPLIT_SHIFT;#这里就给cfg->strtab_base_cfg 赋值 cfg->strtab_base_cfg = reg; return arm_smmu_init_l1_strtab(smmu);}总结一下arm_smmu_init_strtab_2lvl 主要是对arm_smmu_strtab_cfg来进行初始化static int arm_smmu_init_l1_strtab(struct arm_smmu_device *smmu){ unsigned int i; struct arm_smmu_strtab_cfg *cfg = &smmu->strtab_cfg; size_t size = sizeof(*cfg->l1_desc) * cfg->num_l1_ents; void *strtab = smmu->strtab_cfg.strtab; cfg->l1_desc = devm_kzalloc(smmu->dev, size, GFP_KERNEL); if (!cfg->l1_desc) { dev_err(smmu->dev, "failed to allocate l1 stream table desc/n"); return -ENOMEM; } for (i = 0; i < cfg->num_l1_ents; ++i) { #这里将cfg->l1_desc[i] 里面SPAN和L2PTR的值写到strtab 里面。 arm_smmu_write_strtab_l1_desc(strtab, &cfg->l1_desc[i]); strtab += STRTAB_L1_DESC_DWORDS << 3; } return 0;}总结一下arm_smmu_init_l1_strtab 主要是对strtab_cfg.strtab 赋值，我比较疑惑的是这里的cfg->l1_desc 也是刚申请的，理论上cfg->l1_desc 里面是空的才对，不知道为什么要把这里的值写到strtab中.这个疑惑在arm_smmu_add_device 中可以得到解答 /* Check the SIDs are in range of the SMMU and our stream table */ for (i = 0; i < fwspec->num_ids; i++) { u32 sid = fwspec->ids[i]; if (!arm_smmu_sid_in_range(smmu, sid)) return -ERANGE; /* Ensure l2 strtab is initialised */ if (smmu->features & ARM_SMMU_FEAT_2_LVL_STRTAB) { ret = arm_smmu_init_l2_strtab(smmu, sid); if (ret) return ret; } }从上面在这段code中可以看到如果置了ARM_SMMU_FEAT_2_LVL_STRTAB 这个flag，会调用arm_smmu_init_l2_strtabstatic int arm_smmu_init_l2_strtab(struct arm_smmu_device *smmu, u32 sid){ size_t size; void *strtab; struct arm_smmu_strtab_cfg *cfg = &smmu->strtab_cfg; struct arm_smmu_strtab_l1_desc *desc = &cfg->l1_desc[sid >> STRTAB_SPLIT]; if (desc->l2ptr) return 0; size = 1 << (STRTAB_SPLIT + ilog2(STRTAB_STE_DWORDS) + 3); strtab = &cfg->strtab[(sid >> STRTAB_SPLIT) * STRTAB_L1_DESC_DWORDS]; desc->span = STRTAB_SPLIT + 1; desc->l2ptr = dmam_alloc_coherent(smmu->dev, size, &desc->l2ptr_dma, GFP_KERNEL | __GFP_ZERO); if (!desc->l2ptr) { dev_err(smmu->dev, "failed to allocate l2 stream table for SID %u/n", sid); return -ENOMEM; } arm_smmu_init_bypass_stes(desc->l2ptr, 1 << STRTAB_SPLIT); arm_smmu_write_strtab_l1_desc(strtab, desc); return 0;}在arm_smmu_init_l2_strtab 中可以看到会对desc->l2ptr和desc->span 赋值，然后在调用arm_smmu_write_strtab_l1_desc 来写streamtable。这感觉在arm_smmu_init_l1_strtab中调用arm_smmu_write_strtab_l1_desc 没有啥意思.

上一篇：cmake相关

下一篇：暴力修改github项目自动识别语言类型