iommu/arm-smmu-v3: Add second level of context descriptor table

The SMMU can support up to 20 bits of SSID. Add a second level of page
tables to accommodate this. Devices that support more than 1024 SSIDs now
have a table of 1024 L1 entries (8kB), pointing to tables of 1024 context
descriptors (64kB), allocated on demand.
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Will Deacon <will@kernel.org>

drivers/iommu/arm-smmu-v3.c

@@ -223,6 +223,7 @@
 
 #define STRTAB_STE_0_S1FMT		GENMASK_ULL(5, 4)
 #define STRTAB_STE_0_S1FMT_LINEAR	0
+#define STRTAB_STE_0_S1FMT_64K_L2	2
 #define STRTAB_STE_0_S1CTXPTR_MASK	GENMASK_ULL(51, 6)
 #define STRTAB_STE_0_S1CDMAX		GENMASK_ULL(63, 59)
 
@@ -269,7 +270,20 @@
 
 #define STRTAB_STE_3_S2TTB_MASK		GENMASK_ULL(51, 4)
 
-/* Context descriptor (stage-1 only) */
+/*
+ * Context descriptors.
+ *
+ * Linear: when less than 1024 SSIDs are supported
+ * 2lvl: at most 1024 L1 entries,
+ *       1024 lazy entries per table.
+ */
+#define CTXDESC_SPLIT			10
+#define CTXDESC_L2_ENTRIES		(1 << CTXDESC_SPLIT)
+
+#define CTXDESC_L1_DESC_DWORDS		1
+#define CTXDESC_L1_DESC_V		(1UL << 0)
+#define CTXDESC_L1_DESC_L2PTR_MASK	GENMASK_ULL(51, 12)
+
 #define CTXDESC_CD_DWORDS		8
 #define CTXDESC_CD_0_TCR_T0SZ		GENMASK_ULL(5, 0)
 #define CTXDESC_CD_0_TCR_TG0		GENMASK_ULL(7, 6)
@@ -558,9 +572,15 @@ struct arm_smmu_ctx_desc {
 	u64				mair;
 };
 
+struct arm_smmu_l1_ctx_desc {
+	__le64				*l2ptr;
+	dma_addr_t			l2ptr_dma;
+};
+
 struct arm_smmu_ctx_desc_cfg {
 	__le64				*cdtab;
 	dma_addr_t			cdtab_dma;
+	struct arm_smmu_l1_ctx_desc	*l1_desc;
 	unsigned int			num_l1_ents;
 };
 
@@ -1490,6 +1510,57 @@ static void arm_smmu_sync_cd(struct arm_smmu_domain *smmu_domain,
 	arm_smmu_cmdq_issue_sync(smmu);
 }
 
+static int arm_smmu_alloc_cd_leaf_table(struct arm_smmu_device *smmu,
+					struct arm_smmu_l1_ctx_desc *l1_desc)
+{
+	size_t size = CTXDESC_L2_ENTRIES * (CTXDESC_CD_DWORDS << 3);
+
+	l1_desc->l2ptr = dmam_alloc_coherent(smmu->dev, size,
+					     &l1_desc->l2ptr_dma, GFP_KERNEL);
+	if (!l1_desc->l2ptr) {
+		dev_warn(smmu->dev,
+			 "failed to allocate context descriptor table\n");
+		return -ENOMEM;
+	}
+	return 0;
+}
+
+static void arm_smmu_write_cd_l1_desc(__le64 *dst,
+				      struct arm_smmu_l1_ctx_desc *l1_desc)
+{
+	u64 val = (l1_desc->l2ptr_dma & CTXDESC_L1_DESC_L2PTR_MASK) |
+		  CTXDESC_L1_DESC_V;
+
+	WRITE_ONCE(*dst, cpu_to_le64(val));
+}
+
+static __le64 *arm_smmu_get_cd_ptr(struct arm_smmu_domain *smmu_domain,
+				   u32 ssid)
+{
+	__le64 *l1ptr;
+	unsigned int idx;
+	struct arm_smmu_l1_ctx_desc *l1_desc;
+	struct arm_smmu_device *smmu = smmu_domain->smmu;
+	struct arm_smmu_ctx_desc_cfg *cdcfg = &smmu_domain->s1_cfg.cdcfg;
+
+	if (smmu_domain->s1_cfg.s1fmt == STRTAB_STE_0_S1FMT_LINEAR)
+		return cdcfg->cdtab + ssid * CTXDESC_CD_DWORDS;
+
+	idx = ssid >> CTXDESC_SPLIT;
+	l1_desc = &cdcfg->l1_desc[idx];
+	if (!l1_desc->l2ptr) {
+		if (arm_smmu_alloc_cd_leaf_table(smmu, l1_desc))
+			return NULL;
+
+		l1ptr = cdcfg->cdtab + idx * CTXDESC_L1_DESC_DWORDS;
+		arm_smmu_write_cd_l1_desc(l1ptr, l1_desc);
+		/* An invalid L1CD can be cached */
+		arm_smmu_sync_cd(smmu_domain, ssid, false);
+	}
+	idx = ssid & (CTXDESC_L2_ENTRIES - 1);
+	return l1_desc->l2ptr + idx * CTXDESC_CD_DWORDS;
+}
+
 static int arm_smmu_write_ctx_desc(struct arm_smmu_domain *smmu_domain,
 				   int ssid, struct arm_smmu_ctx_desc *cd)
 {
@@ -1504,9 +1575,15 @@ static int arm_smmu_write_ctx_desc(struct arm_smmu_domain *smmu_domain,
 	 */
 	u64 val;
 	bool cd_live;
+	__le64 *cdptr;
 	struct arm_smmu_device *smmu = smmu_domain->smmu;
-	__le64 *cdptr = smmu_domain->s1_cfg.cdcfg.cdtab + ssid *
-			CTXDESC_CD_DWORDS;
+
+	if (WARN_ON(ssid >= (1 << smmu_domain->s1_cfg.s1cdmax)))
+		return -E2BIG;
+
+	cdptr = arm_smmu_get_cd_ptr(smmu_domain, ssid);
+	if (!cdptr)
+		return -ENOMEM;
 
 	val = le64_to_cpu(cdptr[0]);
 	cd_live = !!(val & CTXDESC_CD_0_V);
@@ -1562,29 +1639,78 @@ static int arm_smmu_write_ctx_desc(struct arm_smmu_domain *smmu_domain,
 
 static int arm_smmu_alloc_cd_tables(struct arm_smmu_domain *smmu_domain)
 {
+	int ret;
 	size_t l1size;
+	size_t max_contexts;
 	struct arm_smmu_device *smmu = smmu_domain->smmu;
 	struct arm_smmu_s1_cfg *cfg = &smmu_domain->s1_cfg;
 	struct arm_smmu_ctx_desc_cfg *cdcfg = &cfg->cdcfg;
 
-	cfg->s1fmt = STRTAB_STE_0_S1FMT_LINEAR;
+	max_contexts = 1 << cfg->s1cdmax;
+
+	if (!(smmu->features & ARM_SMMU_FEAT_2_LVL_CDTAB) ||
+	    max_contexts <= CTXDESC_L2_ENTRIES) {
+		cfg->s1fmt = STRTAB_STE_0_S1FMT_LINEAR;
+		cdcfg->num_l1_ents = max_contexts;
+
+		l1size = max_contexts * (CTXDESC_CD_DWORDS << 3);
+	} else {
+		cfg->s1fmt = STRTAB_STE_0_S1FMT_64K_L2;
+		cdcfg->num_l1_ents = DIV_ROUND_UP(max_contexts,
+						  CTXDESC_L2_ENTRIES);
+
+		cdcfg->l1_desc = devm_kcalloc(smmu->dev, cdcfg->num_l1_ents,
+					      sizeof(*cdcfg->l1_desc),
+					      GFP_KERNEL);
+		if (!cdcfg->l1_desc)
+			return -ENOMEM;
+
+		l1size = cdcfg->num_l1_ents * (CTXDESC_L1_DESC_DWORDS << 3);
+	}
 
-	cdcfg->num_l1_ents = 1UL << cfg->s1cdmax;
-	l1size = cdcfg->num_l1_ents * (CTXDESC_CD_DWORDS << 3);
 	cdcfg->cdtab = dmam_alloc_coherent(smmu->dev, l1size, &cdcfg->cdtab_dma,
 					   GFP_KERNEL);
 	if (!cdcfg->cdtab) {
 		dev_warn(smmu->dev, "failed to allocate context descriptor\n");
-		return -ENOMEM;
+		ret = -ENOMEM;
+		goto err_free_l1;
 	}
+
 	return 0;
+
+err_free_l1:
+	if (cdcfg->l1_desc) {
+		devm_kfree(smmu->dev, cdcfg->l1_desc);
+		cdcfg->l1_desc = NULL;
+	}
+	return ret;
 }
 
 static void arm_smmu_free_cd_tables(struct arm_smmu_domain *smmu_domain)
 {
+	int i;
+	size_t size, l1size;
 	struct arm_smmu_device *smmu = smmu_domain->smmu;
 	struct arm_smmu_ctx_desc_cfg *cdcfg = &smmu_domain->s1_cfg.cdcfg;
-	size_t l1size = cdcfg->num_l1_ents * (CTXDESC_CD_DWORDS << 3);
+
+	if (cdcfg->l1_desc) {
+		size = CTXDESC_L2_ENTRIES * (CTXDESC_CD_DWORDS << 3);
+
+		for (i = 0; i < cdcfg->num_l1_ents; i++) {
+			if (!cdcfg->l1_desc[i].l2ptr)
+				continue;
+
+			dmam_free_coherent(smmu->dev, size,
+					   cdcfg->l1_desc[i].l2ptr,
+					   cdcfg->l1_desc[i].l2ptr_dma);
+		}
+		devm_kfree(smmu->dev, cdcfg->l1_desc);
+		cdcfg->l1_desc = NULL;
+
+		l1size = cdcfg->num_l1_ents * (CTXDESC_L1_DESC_DWORDS << 3);
+	} else {
+		l1size = cdcfg->num_l1_ents * (CTXDESC_CD_DWORDS << 3);
+	}
 
 	dmam_free_coherent(smmu->dev, l1size, cdcfg->cdtab, cdcfg->cdtab_dma);
 	cdcfg->cdtab_dma = 0;