scsi: megaraid_sas: Dynamic Raid Map Changes for SAS3.5 Generic Megaraid Controllers

SAS3.5 Generic Megaraid Controllers FW will support new dynamic RaidMap to have different
sizes for different number of supported VDs.

Signed-off-by: Sasikumar Chandrasekaran <sasikumar.pc@broadcom.com>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 261 insertions, 40 deletions

diff --git a/drivers/scsi/megaraid/megaraid_sas_fp.c b/drivers/scsi/megaraid/megaraid_sas_fp.c
index eb9ff444c099..f1384b01b3d3 100644
--- a/drivers/scsi/megaraid/megaraid_sas_fp.c
+++ b/drivers/scsi/megaraid/megaraid_sas_fp.c
@@ -179,18 +179,204 @@ void MR_PopulateDrvRaidMap(struct megasas_instance *instance)
 	struct fusion_context *fusion = instance->ctrl_context;
 	struct MR_FW_RAID_MAP_ALL     *fw_map_old    = NULL;
 	struct MR_FW_RAID_MAP         *pFwRaidMap    = NULL;
-	int i;
+	int i, j;
 	u16 ld_count;
+	struct MR_FW_RAID_MAP_DYNAMIC *fw_map_dyn;
+	struct MR_FW_RAID_MAP_EXT *fw_map_ext;
+	struct MR_RAID_MAP_DESC_TABLE *desc_table;
 
 
 	struct MR_DRV_RAID_MAP_ALL *drv_map =
 			fusion->ld_drv_map[(instance->map_id & 1)];
 	struct MR_DRV_RAID_MAP *pDrvRaidMap = &drv_map->raidMap;
+	void *raid_map_data = NULL;
+
+	memset(drv_map, 0, fusion->drv_map_sz);
+	memset(pDrvRaidMap->ldTgtIdToLd,
+		0xff, (sizeof(u16) * MAX_LOGICAL_DRIVES_DYN));
+
+	if (instance->max_raid_mapsize) {
+		fw_map_dyn = fusion->ld_map[(instance->map_id & 1)];
+#if VD_EXT_DEBUG
+		dev_dbg(&instance->pdev->dev, "raidMapSize 0x%x fw_map_dyn->descTableOffset 0x%x\n",
+			le32_to_cpu(fw_map_dyn->raid_map_size),
+			le32_to_cpu(fw_map_dyn->desc_table_offset));
+		dev_dbg(&instance->pdev->dev, "descTableSize 0x%x descTableNumElements 0x%x\n",
+			le32_to_cpu(fw_map_dyn->desc_table_size),
+			le32_to_cpu(fw_map_dyn->desc_table_num_elements));
+		dev_dbg(&instance->pdev->dev, "drv map %p ldCount %d\n",
+			drv_map, fw_map_dyn->ld_count);
+#endif
+		desc_table =
+		(struct MR_RAID_MAP_DESC_TABLE *)((void *)fw_map_dyn + le32_to_cpu(fw_map_dyn->desc_table_offset));
+		if (desc_table != fw_map_dyn->raid_map_desc_table)
+			dev_dbg(&instance->pdev->dev, "offsets of desc table are not matching desc %p original %p\n",
+				desc_table, fw_map_dyn->raid_map_desc_table);
+
+		ld_count = (u16)le16_to_cpu(fw_map_dyn->ld_count);
+		pDrvRaidMap->ldCount = (__le16)cpu_to_le16(ld_count);
+		pDrvRaidMap->fpPdIoTimeoutSec =
+			fw_map_dyn->fp_pd_io_timeout_sec;
+		pDrvRaidMap->totalSize = sizeof(struct MR_DRV_RAID_MAP_ALL);
+		/* point to actual data starting point*/
+		raid_map_data = (void *)fw_map_dyn +
+			le32_to_cpu(fw_map_dyn->desc_table_offset) +
+			le32_to_cpu(fw_map_dyn->desc_table_size);
+
+		for (i = 0; i < le32_to_cpu(fw_map_dyn->desc_table_num_elements); ++i) {
+
+#if VD_EXT_DEBUG
+			dev_dbg(&instance->pdev->dev, "desc table %p\n",
+				desc_table);
+			dev_dbg(&instance->pdev->dev, "raidmap type %d, raidmapOffset 0x%x\n",
+				desc_table->raid_map_desc_type,
+				desc_table->raid_map_desc_offset);
+			dev_dbg(&instance->pdev->dev, "raid map number of elements 0%x, raidmapsize 0x%x\n",
+				desc_table->raid_map_desc_elements,
+				desc_table->raid_map_desc_buffer_size);
+#endif
+			switch (le32_to_cpu(desc_table->raid_map_desc_type)) {
+			case RAID_MAP_DESC_TYPE_DEVHDL_INFO:
+				fw_map_dyn->dev_hndl_info =
+				(struct MR_DEV_HANDLE_INFO *)(raid_map_data + le32_to_cpu(desc_table->raid_map_desc_offset));
+#if VD_EXT_DEBUG
+				dev_dbg(&instance->pdev->dev, "devHndlInfo  address %p\n",
+					fw_map_dyn->dev_hndl_info);
+#endif
+				memcpy(pDrvRaidMap->devHndlInfo,
+				fw_map_dyn->dev_hndl_info,
+				sizeof(struct MR_DEV_HANDLE_INFO) *
+				le32_to_cpu(desc_table->raid_map_desc_elements));
+			break;
+			case RAID_MAP_DESC_TYPE_TGTID_INFO:
+				fw_map_dyn->ld_tgt_id_to_ld =
+				(u16 *) (raid_map_data +
+				le32_to_cpu(desc_table->raid_map_desc_offset));
+#if VD_EXT_DEBUG
+			dev_dbg(&instance->pdev->dev, "ldTgtIdToLd  address %p\n",
+				fw_map_dyn->ld_tgt_id_to_ld);
+#endif
+			for (j = 0; j < le32_to_cpu(desc_table->raid_map_desc_elements); j++) {
+				pDrvRaidMap->ldTgtIdToLd[j] =
+				fw_map_dyn->ld_tgt_id_to_ld[j];
+#if VD_EXT_DEBUG
+				dev_dbg(&instance->pdev->dev, " %d drv ldTgtIdToLd %d\n",
+					j, pDrvRaidMap->ldTgtIdToLd[j]);
+#endif
+			}
+			break;
+			case RAID_MAP_DESC_TYPE_ARRAY_INFO:
+				fw_map_dyn->ar_map_info =
+				(struct MR_ARRAY_INFO *)
+				(raid_map_data + le32_to_cpu(desc_table->raid_map_desc_offset));
+#if VD_EXT_DEBUG
+				dev_dbg(&instance->pdev->dev, "arMapInfo  address %p\n",
+					fw_map_dyn->ar_map_info);
+#endif
+
+				memcpy(pDrvRaidMap->arMapInfo,
+				fw_map_dyn->ar_map_info,
+				sizeof(struct MR_ARRAY_INFO) * le32_to_cpu(desc_table->raid_map_desc_elements));
+			break;
+			case RAID_MAP_DESC_TYPE_SPAN_INFO:
+				fw_map_dyn->ld_span_map =
+				(struct MR_LD_SPAN_MAP *)
+				(raid_map_data + le32_to_cpu(desc_table->raid_map_desc_offset));
+				memcpy(pDrvRaidMap->ldSpanMap,
+				fw_map_dyn->ld_span_map,
+				sizeof(struct MR_LD_SPAN_MAP) * le32_to_cpu(desc_table->raid_map_desc_elements));
+#if VD_EXT_DEBUG
+				dev_dbg(&instance->pdev->dev, "ldSpanMap  address %p\n",
+					fw_map_dyn->ld_span_map);
+				dev_dbg(&instance->pdev->dev, "MR_LD_SPAN_MAP size 0x%lx\n",
+					sizeof(struct MR_LD_SPAN_MAP));
+				for (j = 0; j < ld_count; j++) {
+					dev_dbg(&instance->pdev->dev, "megaraid_sas(%d) : fw_map_dyn->ldSpanMap[%d].ldRaid.targetId 0x%x\n",
+					j, j, fw_map_dyn->ld_span_map[j].ldRaid.targetId);
+					dev_dbg(&instance->pdev->dev, "fw_map_dyn->ldSpanMap[%d].ldRaid.seqNum 0x%x\n",
+					j, fw_map_dyn->ld_span_map[j].ldRaid.seqNum);
+					dev_dbg(&instance->pdev->dev, "fw_map_dyn->ld_span_map[%d].ldRaid.rowSize 0x%x\n",
+					j, (u32)fw_map_dyn->ld_span_map[j].ldRaid.rowSize);
+
+					dev_dbg(&instance->pdev->dev, "megaraid_sas(%d) :pDrvRaidMap->ldSpanMap[%d].ldRaid.targetId 0x%x\n",
+					j, j, pDrvRaidMap->ldSpanMap[j].ldRaid.targetId);
+					dev_dbg(&instance->pdev->dev, "DrvRaidMap->ldSpanMap[%d].ldRaid.seqNum 0x%x\n",
+					j, pDrvRaidMap->ldSpanMap[j].ldRaid.seqNum);
+					dev_dbg(&instance->pdev->dev, "pDrvRaidMap->ldSpanMap[%d].ldRaid.rowSize 0x%x\n",
+					j, (u32)pDrvRaidMap->ldSpanMap[j].ldRaid.rowSize);
+
+					dev_dbg(&instance->pdev->dev, "megaraid_sas(%d) : drv raid map all %p\n",
+					instance->unique_id, drv_map);
+					dev_dbg(&instance->pdev->dev, "raid map %p LD RAID MAP %p/%p\n",
+					pDrvRaidMap,
+					&fw_map_dyn->ld_span_map[j].ldRaid,
+					&pDrvRaidMap->ldSpanMap[j].ldRaid);
+				}
+#endif
+			break;
+			default:
+				dev_dbg(&instance->pdev->dev, "wrong number of desctableElements %d\n",
+					fw_map_dyn->desc_table_num_elements);
+			}
+			++desc_table;
+		}
+
+	} else if (instance->supportmax256vd) {
+		fw_map_ext =
+		(struct MR_FW_RAID_MAP_EXT *) fusion->ld_map[(instance->map_id & 1)];
+		ld_count = (u16)le16_to_cpu(fw_map_ext->ldCount);
+		if (ld_count > MAX_LOGICAL_DRIVES_EXT) {
+			dev_dbg(&instance->pdev->dev, "megaraid_sas: LD count exposed in RAID map in not valid\n");
+			return;
+		}
+#if VD_EXT_DEBUG
+		for (i = 0; i < ld_count; i++) {
+			dev_dbg(&instance->pdev->dev, "megaraid_sas(%d) :Index 0x%x\n",
+				instance->unique_id, i);
+			dev_dbg(&instance->pdev->dev, "Target Id 0x%x\n",
+				fw_map_ext->ldSpanMap[i].ldRaid.targetId);
+			dev_dbg(&instance->pdev->dev, "Seq Num 0x%x Size 0/%llx\n",
+				fw_map_ext->ldSpanMap[i].ldRaid.seqNum,
+				fw_map_ext->ldSpanMap[i].ldRaid.size);
+		}
+#endif
+
+		pDrvRaidMap->ldCount = (__le16)cpu_to_le16(ld_count);
+		pDrvRaidMap->fpPdIoTimeoutSec = fw_map_ext->fpPdIoTimeoutSec;
+		for (i = 0; i < (MAX_LOGICAL_DRIVES_EXT); i++)
+			pDrvRaidMap->ldTgtIdToLd[i] =
+				(u16)fw_map_ext->ldTgtIdToLd[i];
+		memcpy(pDrvRaidMap->ldSpanMap, fw_map_ext->ldSpanMap,
+				sizeof(struct MR_LD_SPAN_MAP) * ld_count);
+#if VD_EXT_DEBUG
+		for (i = 0; i < ld_count; i++) {
+			dev_dbg(&instance->pdev->dev, "megaraid_sas(%d) : fw_map_ext->ldSpanMap[%d].ldRaid.targetId 0x%x\n",
+			i, i, fw_map_ext->ldSpanMap[i].ldRaid.targetId);
+			dev_dbg(&instance->pdev->dev, "fw_map_ext->ldSpanMap[%d].ldRaid.seqNum 0x%x\n",
+			i, fw_map_ext->ldSpanMap[i].ldRaid.seqNum);
+			dev_dbg(&instance->pdev->dev, "fw_map_ext->ldSpanMap[%d].ldRaid.rowSize 0x%x\n",
+			i, (u32)fw_map_ext->ldSpanMap[i].ldRaid.rowSize);
+
+			dev_dbg(&instance->pdev->dev, "megaraid_sas(%d) : pDrvRaidMap->ldSpanMap[%d].ldRaid.targetId 0x%x\n",
+			i, i, pDrvRaidMap->ldSpanMap[i].ldRaid.targetId);
+			dev_dbg(&instance->pdev->dev, "pDrvRaidMap->ldSpanMap[%d].ldRaid.seqNum 0x%x\n",
+			i, pDrvRaidMap->ldSpanMap[i].ldRaid.seqNum);
+			dev_dbg(&instance->pdev->dev, "pDrvRaidMap->ldSpanMap[%d].ldRaid.rowSize 0x%x\n",
+			i, (u32)pDrvRaidMap->ldSpanMap[i].ldRaid.rowSize);
+
+			dev_dbg(&instance->pdev->dev, "megaraid_sas(%d) : drv raid map all %p\n",
+			instance->unique_id, drv_map);
+			dev_dbg(&instance->pdev->dev, "raid map %p LD RAID MAP %p %p\n",
+			pDrvRaidMap, &fw_map_ext->ldSpanMap[i].ldRaid,
+			&pDrvRaidMap->ldSpanMap[i].ldRaid);
+		}
+#endif
+		memcpy(pDrvRaidMap->arMapInfo, fw_map_ext->arMapInfo,
+			sizeof(struct MR_ARRAY_INFO) * MAX_API_ARRAYS_EXT);
+		memcpy(pDrvRaidMap->devHndlInfo, fw_map_ext->devHndlInfo,
+			sizeof(struct MR_DEV_HANDLE_INFO) *
+					MAX_RAIDMAP_PHYSICAL_DEVICES);
 
-	if (instance->supportmax256vd) {
-		memcpy(fusion->ld_drv_map[instance->map_id & 1],
-			fusion->ld_map[instance->map_id & 1],
-			fusion->current_map_sz);
 		/* New Raid map will not set totalSize, so keep expected value
 		 * for legacy code in ValidateMapInfo
 		 */
@@ -213,16 +399,12 @@ void MR_PopulateDrvRaidMap(struct megasas_instance *instance)
 		}
 #endif
 
-		memset(drv_map, 0, fusion->drv_map_sz);
 		pDrvRaidMap->totalSize = pFwRaidMap->totalSize;
 		pDrvRaidMap->ldCount = (__le16)cpu_to_le16(ld_count);
 		pDrvRaidMap->fpPdIoTimeoutSec = pFwRaidMap->fpPdIoTimeoutSec;
 		for (i = 0; i < MAX_RAIDMAP_LOGICAL_DRIVES + MAX_RAIDMAP_VIEWS; i++)
 			pDrvRaidMap->ldTgtIdToLd[i] =
 				(u8)pFwRaidMap->ldTgtIdToLd[i];
-		for (i = (MAX_RAIDMAP_LOGICAL_DRIVES + MAX_RAIDMAP_VIEWS);
-			i < MAX_LOGICAL_DRIVES_EXT; i++)
-			pDrvRaidMap->ldTgtIdToLd[i] = 0xff;
 		for (i = 0; i < ld_count; i++) {
 			pDrvRaidMap->ldSpanMap[i] = pFwRaidMap->ldSpanMap[i];
 #if VD_EXT_DEBUG
@@ -279,7 +461,9 @@ u8 MR_ValidateMapInfo(struct megasas_instance *instance)
 	lbInfo = fusion->load_balance_info;
 	ldSpanInfo = fusion->log_to_span;
 
-	if (instance->supportmax256vd)
+	if (instance->max_raid_mapsize)
+		expected_size = sizeof(struct MR_DRV_RAID_MAP_ALL);
+	else if (instance->supportmax256vd)
 		expected_size = sizeof(struct MR_FW_RAID_MAP_EXT);
 	else
 		expected_size =
@@ -287,8 +471,10 @@ u8 MR_ValidateMapInfo(struct megasas_instance *instance)
 			(sizeof(struct MR_LD_SPAN_MAP) * le16_to_cpu(pDrvRaidMap->ldCount)));
 
 	if (le32_to_cpu(pDrvRaidMap->totalSize) != expected_size) {
-		dev_err(&instance->pdev->dev, "map info structure size 0x%x is not matching with ld count\n",
-		       (unsigned int) expected_size);
+		dev_dbg(&instance->pdev->dev, "megasas: map info structure size 0x%x",
+			le32_to_cpu(pDrvRaidMap->totalSize));
+		dev_dbg(&instance->pdev->dev, "is not matching expected size 0x%x\n",
+			(unsigned int) expected_size);
 		dev_err(&instance->pdev->dev, "megasas: span map %x, pDrvRaidMap->totalSize : %x\n",
 			(unsigned int)sizeof(struct MR_LD_SPAN_MAP),
 			le32_to_cpu(pDrvRaidMap->totalSize));
@@ -787,7 +973,7 @@ static u8 mr_spanset_get_phy_params(struct megasas_instance *instance, u32 ld,
 			((fusion->adapter_type == THUNDERBOLT_SERIES)  ||
 			((fusion->adapter_type == INVADER_SERIES) &&
 			(raid->regTypeReqOnRead != REGION_TYPE_UNUSED))))
-			pRAID_Context->regLockFlags = REGION_TYPE_EXCLUSIVE;
+			pRAID_Context->reg_lock_flags = REGION_TYPE_EXCLUSIVE;
 		else if (raid->level == 1) {
 			physArm = physArm + 1;
 			pd = MR_ArPdGet(arRef, physArm, map);
@@ -797,9 +983,16 @@ static u8 mr_spanset_get_phy_params(struct megasas_instance *instance, u32 ld,
 	}
 
 	*pdBlock += stripRef + le64_to_cpu(MR_LdSpanPtrGet(ld, span, map)->startBlk);
-	pRAID_Context->spanArm = (span << RAID_CTX_SPANARM_SPAN_SHIFT) |
-					physArm;
-	io_info->span_arm = pRAID_Context->spanArm;
+	if (instance->is_ventura) {
+		((struct RAID_CONTEXT_G35 *) pRAID_Context)->span_arm =
+			(span << RAID_CTX_SPANARM_SPAN_SHIFT) | physArm;
+		io_info->span_arm =
+			(span << RAID_CTX_SPANARM_SPAN_SHIFT) | physArm;
+	} else {
+		pRAID_Context->span_arm =
+			(span << RAID_CTX_SPANARM_SPAN_SHIFT) | physArm;
+		io_info->span_arm = pRAID_Context->span_arm;
+	}
 	return retval;
 }
 
@@ -891,7 +1084,7 @@ u8 MR_GetPhyParams(struct megasas_instance *instance, u32 ld, u64 stripRow,
 			((fusion->adapter_type == THUNDERBOLT_SERIES)  ||
 			((fusion->adapter_type == INVADER_SERIES) &&
 			(raid->regTypeReqOnRead != REGION_TYPE_UNUSED))))
-			pRAID_Context->regLockFlags = REGION_TYPE_EXCLUSIVE;
+			pRAID_Context->reg_lock_flags = REGION_TYPE_EXCLUSIVE;
 		else if (raid->level == 1) {
 			/* Get alternate Pd. */
 			physArm = physArm + 1;
@@ -903,9 +1096,16 @@ u8 MR_GetPhyParams(struct megasas_instance *instance, u32 ld, u64 stripRow,
 	}
 
 	*pdBlock += stripRef + le64_to_cpu(MR_LdSpanPtrGet(ld, span, map)->startBlk);
-	pRAID_Context->spanArm = (span << RAID_CTX_SPANARM_SPAN_SHIFT) |
-		physArm;
-	io_info->span_arm = pRAID_Context->spanArm;
+	if (instance->is_ventura) {
+		((struct RAID_CONTEXT_G35 *) pRAID_Context)->span_arm =
+				(span << RAID_CTX_SPANARM_SPAN_SHIFT) | physArm;
+		io_info->span_arm =
+				(span << RAID_CTX_SPANARM_SPAN_SHIFT) | physArm;
+	} else {
+		pRAID_Context->span_arm =
+			(span << RAID_CTX_SPANARM_SPAN_SHIFT) | physArm;
+		io_info->span_arm = pRAID_Context->span_arm;
+	}
 	return retval;
 }
 
@@ -1109,20 +1309,20 @@ MR_BuildRaidContext(struct megasas_instance *instance,
 			regSize += stripSize;
 	}
 
-	pRAID_Context->timeoutValue =
+	pRAID_Context->timeout_value =
 		cpu_to_le16(raid->fpIoTimeoutForLd ?
 			    raid->fpIoTimeoutForLd :
 			    map->raidMap.fpPdIoTimeoutSec);
 	if (fusion->adapter_type == INVADER_SERIES)
-		pRAID_Context->regLockFlags = (isRead) ?
+		pRAID_Context->reg_lock_flags = (isRead) ?
 			raid->regTypeReqOnRead : raid->regTypeReqOnWrite;
-	else
-		pRAID_Context->regLockFlags = (isRead) ?
+	else if (!instance->is_ventura)
+		pRAID_Context->reg_lock_flags = (isRead) ?
 			REGION_TYPE_SHARED_READ : raid->regTypeReqOnWrite;
-	pRAID_Context->VirtualDiskTgtId = raid->targetId;
-	pRAID_Context->regLockRowLBA    = cpu_to_le64(regStart);
-	pRAID_Context->regLockLength    = cpu_to_le32(regSize);
-	pRAID_Context->configSeqNum	= raid->seqNum;
+	pRAID_Context->virtual_disk_tgt_id = raid->targetId;
+	pRAID_Context->reg_lock_row_lba    = cpu_to_le64(regStart);
+	pRAID_Context->reg_lock_length    = cpu_to_le32(regSize);
+	pRAID_Context->config_seq_num	= raid->seqNum;
 	/* save pointer to raid->LUN array */
 	*raidLUN = raid->LUN;
 
@@ -1140,6 +1340,13 @@ MR_BuildRaidContext(struct megasas_instance *instance,
 		/* If IO on an invalid Pd, then FP is not possible.*/
 		if (io_info->devHandle == cpu_to_le16(MR_PD_INVALID))
 			io_info->fpOkForIo = FALSE;
+		/* if FP possible, set the SLUD bit in
+		 *  regLockFlags for ventura
+		 */
+		else if ((instance->is_ventura) && (!isRead) &&
+			(raid->writeMode == MR_RL_WRITE_BACK_MODE) &&
+			(raid->capability.fp_cache_bypass_capable))
+			((struct RAID_CONTEXT_G35 *) pRAID_Context)->routing_flags.bits.sld = 1;
 		/* set raid 1/10 fast path write capable bit in io_info */
 		if (io_info->fpOkForIo &&
 		    (io_info->r1_alt_dev_handle != MR_PD_INVALID) &&
@@ -1319,6 +1526,7 @@ u8 megasas_get_best_arm_pd(struct megasas_instance *instance,
 	struct fusion_context *fusion;
 	struct MR_LD_RAID  *raid;
 	struct MR_DRV_RAID_MAP_ALL *drv_map;
+	u16	pd1_dev_handle;
 	u16     pend0, pend1, ld;
 	u64     diff0, diff1;
 	u8      bestArm, pd0, pd1, span, arm;
@@ -1344,23 +1552,36 @@ u8 megasas_get_best_arm_pd(struct megasas_instance *instance,
 	pd1 = MR_ArPdGet(arRef, (arm + 1) >= span_row_size ?
 		(arm + 1 - span_row_size) : arm + 1, drv_map);
 
-	/* get the pending cmds for the data and mirror arms */
-	pend0 = atomic_read(&lbInfo->scsi_pending_cmds[pd0]);
-	pend1 = atomic_read(&lbInfo->scsi_pending_cmds[pd1]);
+	/* Get PD1 Dev Handle */
+
+	pd1_dev_handle = MR_PdDevHandleGet(pd1, drv_map);
+
+	if (pd1_dev_handle == MR_PD_INVALID) {
+		bestArm = arm;
+	} else {
+		/* get the pending cmds for the data and mirror arms */
+		pend0 = atomic_read(&lbInfo->scsi_pending_cmds[pd0]);
+		pend1 = atomic_read(&lbInfo->scsi_pending_cmds[pd1]);
 
-	/* Determine the disk whose head is nearer to the req. block */
-	diff0 = ABS_DIFF(block, lbInfo->last_accessed_block[pd0]);
-	diff1 = ABS_DIFF(block, lbInfo->last_accessed_block[pd1]);
-	bestArm = (diff0 <= diff1 ? arm : arm ^ 1);
+		/* Determine the disk whose head is nearer to the req. block */
+		diff0 = ABS_DIFF(block, lbInfo->last_accessed_block[pd0]);
+		diff1 = ABS_DIFF(block, lbInfo->last_accessed_block[pd1]);
+		bestArm = (diff0 <= diff1 ? arm : arm ^ 1);
 
-	if ((bestArm == arm && pend0 > pend1 + lb_pending_cmds)  ||
+		/* Make balance count from 16 to 4 to
+		 *  keep driver in sync with Firmware
+		 */
+		if ((bestArm == arm && pend0 > pend1 + lb_pending_cmds)  ||
 			(bestArm != arm && pend1 > pend0 + lb_pending_cmds))
-		bestArm ^= 1;
+			bestArm ^= 1;
+
+		/* Update the last accessed block on the correct pd */
+		io_info->span_arm =
+			(span << RAID_CTX_SPANARM_SPAN_SHIFT) | bestArm;
+		io_info->pd_after_lb = (bestArm == arm) ? pd0 : pd1;
+	}
 
-	/* Update the last accessed block on the correct pd */
-	io_info->pd_after_lb = (bestArm == arm) ? pd0 : pd1;
 	lbInfo->last_accessed_block[io_info->pd_after_lb] = block + count - 1;
-	io_info->span_arm = (span << RAID_CTX_SPANARM_SPAN_SHIFT) | bestArm;
 #if SPAN_DEBUG
 	if (arm != bestArm)
 		dev_dbg(&instance->pdev->dev, "LSI Debug R1 Load balance "