scsi: cxlflash: Improve asynchronous interrupt processing

The method used to decode asynchronous interrupts involves unnecessary loops
to match up bits that are set with corresponding entries in the asynchronous
interrupt information table. This algorithm is wasteful and does not scale
well as new status bits are supported.

As an improvement, use the for_each_set_bit() service to iterate over the
asynchronous status bits and refactor the information table such that it can
be indexed by bit position.

Signed-off-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Signed-off-by: Uma Krishnan <ukrishn@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/cxlflash/main.c

@@ -1017,52 +1017,6 @@ static void afu_link_reset(struct afu *afu, int port, __be64 __iomem *fc_regs)
 	dev_dbg(dev, "%s: returning port_sel=%016llx\n", __func__, port_sel);
 }
 
-/*
- * Asynchronous interrupt information table
- *
- * NOTE: The checkpatch script considers the BUILD_SISL_ASTATUS_FC_PORT macro
- * as complex and complains because it is not wrapped with parentheses/braces.
- */
-#define ASTATUS_FC(_a, _b, _c, _d)					 \
-	{ SISL_ASTATUS_FC##_a##_##_b, _c, _a, (_d) }
-
-#define BUILD_SISL_ASTATUS_FC_PORT(_a)					 \
-	ASTATUS_FC(_a, OTHER, "other error", CLR_FC_ERROR | LINK_RESET), \
-	ASTATUS_FC(_a, LOGO, "target initiated LOGO", 0),		 \
-	ASTATUS_FC(_a, CRC_T, "CRC threshold exceeded", LINK_RESET),	 \
-	ASTATUS_FC(_a, LOGI_R, "login timed out, retrying", LINK_RESET), \
-	ASTATUS_FC(_a, LOGI_F, "login failed", CLR_FC_ERROR),		 \
-	ASTATUS_FC(_a, LOGI_S, "login succeeded", SCAN_HOST),		 \
-	ASTATUS_FC(_a, LINK_DN, "link down", 0),			 \
-	ASTATUS_FC(_a, LINK_UP, "link up", 0)
-
-static const struct asyc_intr_info ainfo[] = {
-	BUILD_SISL_ASTATUS_FC_PORT(2),
-	BUILD_SISL_ASTATUS_FC_PORT(3),
-	BUILD_SISL_ASTATUS_FC_PORT(0),
-	BUILD_SISL_ASTATUS_FC_PORT(1),
-	{ 0x0, "", 0, 0 }
-};
-
-/**
- * find_ainfo() - locates and returns asynchronous interrupt information
- * @status:	Status code set by AFU on error.
- *
- * Return: The located information or NULL when the status code is invalid.
- */
-static const struct asyc_intr_info *find_ainfo(u64 status)
-{
-	const struct asyc_intr_info *info;
-
-	BUILD_BUG_ON(ainfo[ARRAY_SIZE(ainfo) - 1].status != 0);
-
-	for (info = &ainfo[0]; info->status; info++)
-		if (info->status == status)
-			return info;
-
-	return NULL;
-}
-
 /**
  * afu_err_intr_init() - clears and initializes the AFU for error interrupts
  * @afu:	AFU associated with the host.
@@ -1293,6 +1247,35 @@ static irqreturn_t cxlflash_rrq_irq(int irq, void *data)
 	return IRQ_HANDLED;
 }
 
+/*
+ * Asynchronous interrupt information table
+ *
+ * NOTE:
+ *	- Order matters here as this array is indexed by bit position.
+ *
+ *	- The checkpatch script considers the BUILD_SISL_ASTATUS_FC_PORT macro
+ *	  as complex and complains due to a lack of parentheses/braces.
+ */
+#define ASTATUS_FC(_a, _b, _c, _d)					 \
+	{ SISL_ASTATUS_FC##_a##_##_b, _c, _a, (_d) }
+
+#define BUILD_SISL_ASTATUS_FC_PORT(_a)					 \
+	ASTATUS_FC(_a, LINK_UP, "link up", 0),				 \
+	ASTATUS_FC(_a, LINK_DN, "link down", 0),			 \
+	ASTATUS_FC(_a, LOGI_S, "login succeeded", SCAN_HOST),		 \
+	ASTATUS_FC(_a, LOGI_F, "login failed", CLR_FC_ERROR),		 \
+	ASTATUS_FC(_a, LOGI_R, "login timed out, retrying", LINK_RESET), \
+	ASTATUS_FC(_a, CRC_T, "CRC threshold exceeded", LINK_RESET),	 \
+	ASTATUS_FC(_a, LOGO, "target initiated LOGO", 0),		 \
+	ASTATUS_FC(_a, OTHER, "other error", CLR_FC_ERROR | LINK_RESET)
+
+static const struct asyc_intr_info ainfo[] = {
+	BUILD_SISL_ASTATUS_FC_PORT(1),
+	BUILD_SISL_ASTATUS_FC_PORT(0),
+	BUILD_SISL_ASTATUS_FC_PORT(3),
+	BUILD_SISL_ASTATUS_FC_PORT(2)
+};
+
 /**
  * cxlflash_async_err_irq() - interrupt handler for asynchronous errors
  * @irq:	Interrupt number.
@@ -1305,18 +1288,18 @@ static irqreturn_t cxlflash_async_err_irq(int irq, void *data)
 	struct afu *afu = (struct afu *)data;
 	struct cxlflash_cfg *cfg = afu->parent;
 	struct device *dev = &cfg->dev->dev;
-	u64 reg_unmasked;
 	const struct asyc_intr_info *info;
 	struct sisl_global_map __iomem *global = &afu->afu_map->global;
 	__be64 __iomem *fc_port_regs;
+	u64 reg_unmasked;
 	u64 reg;
+	u64 bit;
 	u8 port;
-	int i;
 
 	reg = readq_be(&global->regs.aintr_status);
 	reg_unmasked = (reg & SISL_ASTATUS_UNMASK);
 
-	if (reg_unmasked == 0) {
+	if (unlikely(reg_unmasked == 0)) {
 		dev_err(dev, "%s: spurious interrupt, aintr_status=%016llx\n",
 			__func__, reg);
 		goto out;
@@ -1326,10 +1309,17 @@ static irqreturn_t cxlflash_async_err_irq(int irq, void *data)
 	writeq_be(reg_unmasked, &global->regs.aintr_clear);
 
 	/* Check each bit that is on */
-	for (i = 0; reg_unmasked; i++, reg_unmasked = (reg_unmasked >> 1)) {
-		info = find_ainfo(1ULL << i);
-		if (((reg_unmasked & 0x1) == 0) || !info)
+	for_each_set_bit(bit, (ulong *)&reg_unmasked, BITS_PER_LONG) {
+		if (unlikely(bit >= ARRAY_SIZE(ainfo))) {
+			WARN_ON_ONCE(1);
 			continue;
+		}
+
+		info = &ainfo[bit];
+		if (unlikely(info->status != 1ULL << bit)) {
+			WARN_ON_ONCE(1);
+			continue;
+		}
 
 		port = info->port;
 		fc_port_regs = get_fc_port_regs(cfg, port);