iommu/arm-smmu: Add a stream map entry iterator

We iterate over the SMEs associated with a master config quite a lot in
various places, and are about to do so even more. Let's wrap the idiom
in a handy iterator macro before the repetition gets out of hand.
Tested-by: NLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: NRobin Murphy <robin.murphy@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

drivers/iommu/arm-smmu.c

@@ -324,6 +324,8 @@ struct arm_smmu_master_cfg {
 	s16				smendx[MAX_MASTER_STREAMIDS];
 };
 #define INVALID_SMENDX			-1
+#define for_each_cfg_sme(cfg, i, idx) \
+	for (i = 0; idx = cfg->smendx[i], i < cfg->num_streamids; ++i)
 
 struct arm_smmu_device {
 	struct device			*dev;
@@ -1090,8 +1092,8 @@ static int arm_smmu_master_alloc_smes(struct arm_smmu_device *smmu,
 	int i, idx;
 
 	/* Allocate the SMRs on the SMMU */
-	for (i = 0; i < cfg->num_streamids; ++i) {
-		if (cfg->smendx[i] != INVALID_SMENDX)
+	for_each_cfg_sme(cfg, i, idx) {
+		if (idx != INVALID_SMENDX)
 			return -EEXIST;
 
 		/* ...except on stream indexing hardware, of course */
@@ -1115,8 +1117,8 @@ static int arm_smmu_master_alloc_smes(struct arm_smmu_device *smmu,
 		return 0;
 
 	/* It worked! Now, poke the actual hardware */
-	for (i = 0; i < cfg->num_streamids; ++i)
-		arm_smmu_write_smr(smmu, cfg->smendx[i]);
+	for_each_cfg_sme(cfg, i, idx)
+		arm_smmu_write_smr(smmu, idx);
 
 	return 0;
 
@@ -1131,15 +1133,13 @@ static int arm_smmu_master_alloc_smes(struct arm_smmu_device *smmu,
 static void arm_smmu_master_free_smes(struct arm_smmu_master_cfg *cfg)
 {
 	struct arm_smmu_device *smmu = cfg->smmu;
-	int i;
+	int i, idx;
 
 	/*
 	 * We *must* clear the S2CR first, because freeing the SMR means
 	 * that it can be re-allocated immediately.
 	 */
-	for (i = 0; i < cfg->num_streamids; ++i) {
-		int idx = cfg->smendx[i];
-
+	for_each_cfg_sme(cfg, i, idx) {
 		/* An IOMMU group is torn down by the first device to be removed */
 		if (idx == INVALID_SMENDX)
 			return;
@@ -1151,9 +1151,9 @@ static void arm_smmu_master_free_smes(struct arm_smmu_master_cfg *cfg)
 	__iowmb();
 
 	/* Invalidate the SMRs before freeing back to the allocator */
-	for (i = 0; i < cfg->num_streamids; ++i) {
+	for_each_cfg_sme(cfg, i, idx) {
 		if (smmu->smrs)
-			arm_smmu_free_smr(smmu, cfg->smendx[i]);
+			arm_smmu_free_smr(smmu, idx);
 
 		cfg->smendx[i] = INVALID_SMENDX;
 	}
@@ -1162,7 +1162,7 @@ static void arm_smmu_master_free_smes(struct arm_smmu_master_cfg *cfg)
 static int arm_smmu_domain_add_master(struct arm_smmu_domain *smmu_domain,
 				      struct arm_smmu_master_cfg *cfg)
 {
-	int i, ret = 0;
+	int i, idx, ret = 0;
 	struct arm_smmu_device *smmu = smmu_domain->smmu;
 	struct arm_smmu_s2cr *s2cr = smmu->s2crs;
 	enum arm_smmu_s2cr_type type = S2CR_TYPE_TRANS;
@@ -1182,9 +1182,7 @@ static int arm_smmu_domain_add_master(struct arm_smmu_domain *smmu_domain,
 	if (smmu_domain->domain.type == IOMMU_DOMAIN_DMA)
 		type = S2CR_TYPE_BYPASS;
 
-	for (i = 0; i < cfg->num_streamids; ++i) {
-		int idx = cfg->smendx[i];
-
+	for_each_cfg_sme(cfg, i, idx) {
 		/* Devices in an IOMMU group may already be configured */
 		if (type == s2cr[idx].type && cbndx == s2cr[idx].cbndx)
 			break;