iommu/arm-smmu: Decouple context format from kernel config

The way the driver currently forces an AArch32 or AArch64 context format
based on the kernel config and SMMU architecture version is suboptimal,
in that it makes it very hard to support oddball mix-and-match cases
like the SMMUv1 64KB supplement, or situations where the reduced table
depth of an AArch32 short descriptor context may be desirable under an
AArch64 kernel. It also only happens to work on current implementations
which do support all the relevant formats.

Introduce an explicit notion of context format, so we can manage that
independently and get rid of the inflexible #ifdeffery.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

drivers/iommu/arm-smmu.c

@@ -117,6 +117,8 @@
 #define ID0_NTS				(1 << 28)
 #define ID0_SMS				(1 << 27)
 #define ID0_ATOSNS			(1 << 26)
+#define ID0_PTFS_NO_AARCH32		(1 << 25)
+#define ID0_PTFS_NO_AARCH32S		(1 << 24)
 #define ID0_CTTW			(1 << 14)
 #define ID0_NUMIRPT_SHIFT		16
 #define ID0_NUMIRPT_MASK		0xff
@@ -317,6 +319,11 @@ struct arm_smmu_device {
 #define ARM_SMMU_FEAT_TRANS_NESTED	(1 << 4)
 #define ARM_SMMU_FEAT_TRANS_OPS		(1 << 5)
 #define ARM_SMMU_FEAT_VMID16		(1 << 6)
+#define ARM_SMMU_FEAT_FMT_AARCH64_4K	(1 << 7)
+#define ARM_SMMU_FEAT_FMT_AARCH64_16K	(1 << 8)
+#define ARM_SMMU_FEAT_FMT_AARCH64_64K	(1 << 9)
+#define ARM_SMMU_FEAT_FMT_AARCH32_L	(1 << 10)
+#define ARM_SMMU_FEAT_FMT_AARCH32_S	(1 << 11)
 	u32				features;
 
 #define ARM_SMMU_OPT_SECURE_CFG_ACCESS (1 << 0)
@@ -346,10 +353,18 @@ struct arm_smmu_device {
 	u32				cavium_id_base; /* Specific to Cavium */
 };
 
+enum arm_smmu_context_fmt {
+	ARM_SMMU_CTX_FMT_NONE,
+	ARM_SMMU_CTX_FMT_AARCH64,
+	ARM_SMMU_CTX_FMT_AARCH32_L,
+	ARM_SMMU_CTX_FMT_AARCH32_S,
+};
+
 struct arm_smmu_cfg {
 	u8				cbndx;
 	u8				irptndx;
 	u32				cbar;
+	enum arm_smmu_context_fmt	fmt;
 };
 #define INVALID_IRPTNDX			0xff
 
@@ -619,14 +634,13 @@ static void arm_smmu_tlb_inv_range_nosync(unsigned long iova, size_t size,
 		reg = ARM_SMMU_CB_BASE(smmu) + ARM_SMMU_CB(smmu, cfg->cbndx);
 		reg += leaf ? ARM_SMMU_CB_S1_TLBIVAL : ARM_SMMU_CB_S1_TLBIVA;
 
-		if (!IS_ENABLED(CONFIG_64BIT) || smmu->version == ARM_SMMU_V1) {
+		if (cfg->fmt != ARM_SMMU_CTX_FMT_AARCH64) {
 			iova &= ~12UL;
 			iova |= ARM_SMMU_CB_ASID(smmu, cfg);
 			do {
 				writel_relaxed(iova, reg);
 				iova += granule;
 			} while (size -= granule);
-#ifdef CONFIG_64BIT
 		} else {
 			iova >>= 12;
 			iova |= (u64)ARM_SMMU_CB_ASID(smmu, cfg) << 48;
@@ -634,9 +648,7 @@ static void arm_smmu_tlb_inv_range_nosync(unsigned long iova, size_t size,
 				writeq_relaxed(iova, reg);
 				iova += granule >> 12;
 			} while (size -= granule);
-#endif
 		}
-#ifdef CONFIG_64BIT
 	} else if (smmu->version == ARM_SMMU_V2) {
 		reg = ARM_SMMU_CB_BASE(smmu) + ARM_SMMU_CB(smmu, cfg->cbndx);
 		reg += leaf ? ARM_SMMU_CB_S2_TLBIIPAS2L :
@@ -646,7 +658,6 @@ static void arm_smmu_tlb_inv_range_nosync(unsigned long iova, size_t size,
 			smmu_write_atomic_lq(iova, reg);
 			iova += granule >> 12;
 		} while (size -= granule);
-#endif
 	} else {
 		reg = ARM_SMMU_GR0(smmu) + ARM_SMMU_GR0_TLBIVMID;
 		writel_relaxed(ARM_SMMU_CB_VMID(smmu, cfg), reg);
@@ -745,11 +756,10 @@ static void arm_smmu_init_context_bank(struct arm_smmu_domain *smmu_domain,
 	cb_base = ARM_SMMU_CB_BASE(smmu) + ARM_SMMU_CB(smmu, cfg->cbndx);
 
 	if (smmu->version > ARM_SMMU_V1) {
-#ifdef CONFIG_64BIT
+		if (cfg->fmt == ARM_SMMU_CTX_FMT_AARCH64)
 			reg = CBA2R_RW64_64BIT;
-#else
+		else
 			reg = CBA2R_RW64_32BIT;
-#endif
 		/* 16-bit VMIDs live in CBA2R */
 		if (smmu->features & ARM_SMMU_FEAT_VMID16)
 			reg |= ARM_SMMU_CB_VMID(smmu, cfg) << CBA2R_VMID_SHIFT;
@@ -860,16 +870,40 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
 	if (!(smmu->features & ARM_SMMU_FEAT_TRANS_S2))
 		smmu_domain->stage = ARM_SMMU_DOMAIN_S1;
 
+	/*
+	 * Choosing a suitable context format is even more fiddly. Until we
+	 * grow some way for the caller to express a preference, and/or move
+	 * the decision into the io-pgtable code where it arguably belongs,
+	 * just aim for the closest thing to the rest of the system, and hope
+	 * that the hardware isn't esoteric enough that we can't assume AArch64
+	 * support to be a superset of AArch32 support...
+	 */
+	if (smmu->features & ARM_SMMU_FEAT_FMT_AARCH32_L)
+		cfg->fmt = ARM_SMMU_CTX_FMT_AARCH32_L;
+	if ((IS_ENABLED(CONFIG_64BIT) || cfg->fmt == ARM_SMMU_CTX_FMT_NONE) &&
+	    (smmu->features & (ARM_SMMU_FEAT_FMT_AARCH64_64K |
+			       ARM_SMMU_FEAT_FMT_AARCH64_16K |
+			       ARM_SMMU_FEAT_FMT_AARCH64_4K)))
+		cfg->fmt = ARM_SMMU_CTX_FMT_AARCH64;
+
+	if (cfg->fmt == ARM_SMMU_CTX_FMT_NONE) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
 	switch (smmu_domain->stage) {
 	case ARM_SMMU_DOMAIN_S1:
 		cfg->cbar = CBAR_TYPE_S1_TRANS_S2_BYPASS;
 		start = smmu->num_s2_context_banks;
 		ias = smmu->va_size;
 		oas = smmu->ipa_size;
-		if (IS_ENABLED(CONFIG_64BIT))
+		if (cfg->fmt == ARM_SMMU_CTX_FMT_AARCH64) {
 			fmt = ARM_64_LPAE_S1;
-		else
+		} else {
 			fmt = ARM_32_LPAE_S1;
+			ias = min(ias, 32UL);
+			oas = min(oas, 40UL);
+		}
 		break;
 	case ARM_SMMU_DOMAIN_NESTED:
 		/*
@@ -881,10 +915,13 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
 		start = 0;
 		ias = smmu->ipa_size;
 		oas = smmu->pa_size;
-		if (IS_ENABLED(CONFIG_64BIT))
+		if (cfg->fmt == ARM_SMMU_CTX_FMT_AARCH64) {
 			fmt = ARM_64_LPAE_S2;
-		else
+		} else {
 			fmt = ARM_32_LPAE_S2;
+			ias = min(ias, 40UL);
+			oas = min(oas, 40UL);
+		}
 		break;
 	default:
 		ret = -EINVAL;
@@ -1670,6 +1707,12 @@ static int arm_smmu_device_cfg_probe(struct arm_smmu_device *smmu)
 					   ID0_NUMSIDB_MASK;
 	}
 
+	if (smmu->version < ARM_SMMU_V2 || !(id & ID0_PTFS_NO_AARCH32)) {
+		smmu->features |= ARM_SMMU_FEAT_FMT_AARCH32_L;
+		if (!(id & ID0_PTFS_NO_AARCH32S))
+			smmu->features |= ARM_SMMU_FEAT_FMT_AARCH32_S;
+	}
+
 	/* ID1 */
 	id = readl_relaxed(gr0_base + ARM_SMMU_GR0_ID1);
 	smmu->pgshift = (id & ID1_PAGESIZE) ? 16 : 12;
@@ -1725,22 +1768,29 @@ static int arm_smmu_device_cfg_probe(struct arm_smmu_device *smmu)
 
 	if (smmu->version == ARM_SMMU_V1) {
 		smmu->va_size = smmu->ipa_size;
-		size = SZ_4K | SZ_2M | SZ_1G;
 	} else {
 		size = (id >> ID2_UBS_SHIFT) & ID2_UBS_MASK;
 		smmu->va_size = arm_smmu_id_size_to_bits(size);
-#ifndef CONFIG_64BIT
-		smmu->va_size = min(32UL, smmu->va_size);
-#endif
-		size = 0;
 		if (id & ID2_PTFS_4K)
-			size |= SZ_4K | SZ_2M | SZ_1G;
+			smmu->features |= ARM_SMMU_FEAT_FMT_AARCH64_4K;
 		if (id & ID2_PTFS_16K)
-			size |= SZ_16K | SZ_32M;
+			smmu->features |= ARM_SMMU_FEAT_FMT_AARCH64_16K;
 		if (id & ID2_PTFS_64K)
-			size |= SZ_64K | SZ_512M;
+			smmu->features |= ARM_SMMU_FEAT_FMT_AARCH64_64K;
 	}
 
+	/* Now we've corralled the various formats, what'll it do? */
+	size = 0;
+	if (smmu->features & ARM_SMMU_FEAT_FMT_AARCH32_S)
+		size |= SZ_4K | SZ_64K | SZ_1M | SZ_16M;
+	if (smmu->features &
+	    (ARM_SMMU_FEAT_FMT_AARCH32_L | ARM_SMMU_FEAT_FMT_AARCH64_4K))
+		size |= SZ_4K | SZ_2M | SZ_1G;
+	if (smmu->features & ARM_SMMU_FEAT_FMT_AARCH64_16K)
+		size |= SZ_16K | SZ_32M;
+	if (smmu->features & ARM_SMMU_FEAT_FMT_AARCH64_64K)
+		size |= SZ_64K | SZ_512M;
+
 	arm_smmu_ops.pgsize_bitmap &= size;
 	dev_notice(smmu->dev, "\tSupported page sizes: 0x%08lx\n", size);