smmu學(xué)習(xí)筆記之streamtable

2019-11-06 09:45:50

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streamtable有兩種組織方式，根據(jù)ARM_SMMU_FEAT_2_LVL_STRTAB來判斷而這個(gè)flag是在arm_smmu_device_hw_PRobe 中通過讀取ARM_SMMU_IDR0 這個(gè)寄存器來判斷的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 中就根據(jù)這個(gè)flag 將streamtable分成兩種組織方式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;}不管采用哪種streamtable，都會(huì)對smmu->strtab_cfg.strtab_dma賦值，最后將smmu->strtab_cfg.strtab_dma 保存到smmu->strtab_cfg.strtab_base 中。我們先來看arm_smmu_init_strtab_2lvlstatic int arm_smmu_init_strtab_2lvl(struct arm_smmu_device *smmu){ void *strtab; u64 reg; u32 size, l1size;//讓cfg 指針指向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); }#計(jì)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);#為strtab 申請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;#這里就給cfg->strtab_base_cfg 賦值 cfg->strtab_base_cfg = reg; return arm_smmu_init_l1_strtab(smmu);}總結(jié)一下arm_smmu_init_strtab_2lvl 主要是對arm_smmu_strtab_cfg來進(jìn)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) { #這里將cfg->l1_desc[i] 里面SPAN和L2PTR的值寫到strtab 里面。 arm_smmu_write_strtab_l1_desc(strtab, &cfg->l1_desc[i]); strtab += STRTAB_L1_DESC_DWORDS << 3; } return 0;}總結(jié)一下arm_smmu_init_l1_strtab 主要是對strtab_cfg.strtab 賦值，我比較疑惑的是這里的cfg->l1_desc 也是剛申請的，理論上cfg->l1_desc 里面是空的才對，不知道為什么要把這里的值寫到strtab中.這個(gè)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; } }從上面在這段code中可以看到如果置了ARM_SMMU_FEAT_2_LVL_STRTAB 這個(gè)flag，會(huì)調(diào)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 中可以看到會(huì)對desc->l2ptr和desc->span 賦值，然后在調(diào)用arm_smmu_write_strtab_l1_desc 來寫streamtable。這感覺在arm_smmu_init_l1_strtab中調(diào)用arm_smmu_write_strtab_l1_desc 沒有啥意思.

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