[SCSI] megaraid_sas: Add 9565/9285 specific code

This patch adds MegaRAID 9265/9285 (Device id 0x5b) specific code
Signed-off-by: NAdam Radford <aradford@gmail.com>
Signed-off-by: NJames Bottomley <James.Bottomley@suse.de>

drivers/scsi/megaraid/Makefile

 obj-$(CONFIG_MEGARAID_MM)	+= megaraid_mm.o
 obj-$(CONFIG_MEGARAID_MAILBOX)	+= megaraid_mbox.o
 obj-$(CONFIG_MEGARAID_SAS)	+= megaraid_sas.o
-megaraid_sas-objs := megaraid_sas_base.o
+megaraid_sas-objs := megaraid_sas_base.o megaraid_sas_fusion.o \
+	megaraid_sas_fp.o

drivers/scsi/megaraid/megaraid_sas.h

@@ -33,9 +33,9 @@
 /*
  * MegaRAID SAS Driver meta data
  */
-#define MEGASAS_VERSION			"00.00.04.31-rc1"
-#define MEGASAS_RELDATE			"May 3, 2010"
-#define MEGASAS_EXT_VERSION		"Mon. May 3, 11:41:51 PST 2010"
+#define MEGASAS_VERSION				"00.00.05.29-rc1"
+#define MEGASAS_RELDATE				"Dec. 7, 2010"
+#define MEGASAS_EXT_VERSION			"Tue. Dec. 7 17:00:00 PDT 2010"
 
 /*
  * Device IDs
@@ -47,6 +47,7 @@
 #define	PCI_DEVICE_ID_LSI_SAS0079GEN2		0x0079
 #define	PCI_DEVICE_ID_LSI_SAS0073SKINNY		0x0073
 #define	PCI_DEVICE_ID_LSI_SAS0071SKINNY		0x0071
+#define	PCI_DEVICE_ID_LSI_FUSION		0x005b
 
 /*
  * =====================================
@@ -436,7 +437,6 @@ struct megasas_ctrl_prop {
 	* Add properties that can be controlled by
 	* a bit in the following structure.
 	*/
-
 	struct {
 		u32     copyBackDisabled            : 1;
 		u32     SMARTerEnabled              : 1;
@@ -716,6 +716,7 @@ struct megasas_ctrl_info {
 #define MEGASAS_DEFAULT_INIT_ID			-1
 #define MEGASAS_MAX_LUN				8
 #define MEGASAS_MAX_LD				64
+#define MEGASAS_DEFAULT_CMD_PER_LUN		128
 #define MEGASAS_MAX_PD                          (MEGASAS_MAX_PD_CHANNELS * \
 						MEGASAS_MAX_DEV_PER_CHANNEL)
 #define MEGASAS_MAX_LD_IDS			(MEGASAS_MAX_LD_CHANNELS * \
@@ -784,7 +785,10 @@ struct megasas_ctrl_info {
 */
  
 struct megasas_register_set {
-	u32 	reserved_0[4];			/*0000h*/
+	u32	doorbell;                       /*0000h*/
+	u32	fusion_seq_offset;		/*0004h*/
+	u32	fusion_host_diag;		/*0008h*/
+	u32	reserved_01;			/*000Ch*/
 
 	u32 	inbound_msg_0;			/*0010h*/
 	u32 	inbound_msg_1;			/*0014h*/
@@ -804,15 +808,18 @@ struct megasas_register_set {
 	u32 	inbound_queue_port;		/*0040h*/
 	u32 	outbound_queue_port;		/*0044h*/
 
-	u32 	reserved_2[22];			/*0048h*/
+	u32	reserved_2[9];			/*0048h*/
+	u32	reply_post_host_index;		/*006Ch*/
+	u32	reserved_2_2[12];		/*0070h*/
 
 	u32 	outbound_doorbell_clear;	/*00A0h*/
 
 	u32 	reserved_3[3];			/*00A4h*/
 
 	u32 	outbound_scratch_pad ;		/*00B0h*/
+	u32	outbound_scratch_pad_2;         /*00B4h*/
 
-	u32 	reserved_4[3];			/*00B4h*/
+	u32	reserved_4[2];			/*00B8h*/
 
 	u32 	inbound_low_queue_port ;	/*00C0h*/
 
@@ -1287,6 +1294,9 @@ struct megasas_instance {
 
 	u16 max_num_sge;
 	u16 max_fw_cmds;
+	/* For Fusion its num IOCTL cmds, for others MFI based its
+	   max_fw_cmds */
+	u16 max_mfi_cmds;
 	u32 max_sectors_per_req;
 	struct megasas_aen_event *ev;
 
@@ -1336,9 +1346,15 @@ struct megasas_instance {
 	struct timer_list io_completion_timer;
 	struct list_head internal_reset_pending_q;
 
+	/* Ptr to hba specfic information */
+	void *ctrl_context;
 	u8	msi_flag;
 	struct msix_entry msixentry;
+	u64 map_id;
+	struct megasas_cmd *map_update_cmd;
 	unsigned long bar;
+	long reset_flags;
+	struct mutex reset_mutex;
 };
 
 enum {
@@ -1397,7 +1413,13 @@ struct megasas_cmd {
 	struct list_head list;
 	struct scsi_cmnd *scmd;
 	struct megasas_instance *instance;
-	u32 frame_count;
+	union {
+		struct {
+			u16 smid;
+			u16 resvd;
+		} context;
+		u32 frame_count;
+	};
 };
 
 #define MAX_MGMT_ADAPTERS		1024

drivers/scsi/megaraid/megaraid_sas_fp.c

+/*
+ *  Linux MegaRAID driver for SAS based RAID controllers
+ *
+ *  Copyright (c) 2009-2011  LSI Corporation.
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License
+ *  as published by the Free Software Foundation; either version 2
+ *  of the License, or (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ *  FILE: megaraid_sas_fp.c
+ *
+ *  Authors: LSI Corporation
+ *           Sumant Patro
+ *           Varad Talamacki
+ *           Manoj Jose
+ *
+ *  Send feedback to: <megaraidlinux@lsi.com>
+ *
+ *  Mail to: LSI Corporation, 1621 Barber Lane, Milpitas, CA 95035
+ *     ATTN: Linuxraid
+ */
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/pci.h>
+#include <linux/list.h>
+#include <linux/moduleparam.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <linux/interrupt.h>
+#include <linux/delay.h>
+#include <linux/smp_lock.h>
+#include <linux/uio.h>
+#include <linux/uaccess.h>
+#include <linux/fs.h>
+#include <linux/compat.h>
+#include <linux/blkdev.h>
+#include <linux/poll.h>
+
+#include <scsi/scsi.h>
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi_host.h>
+
+#include "megaraid_sas_fusion.h"
+#include <asm/div64.h>
+
+#define ABS_DIFF(a, b)   (((a) > (b)) ? ((a) - (b)) : ((b) - (a)))
+#define MR_LD_STATE_OPTIMAL 3
+#define FALSE 0
+#define TRUE 1
+
+/* Prototypes */
+void
+mr_update_load_balance_params(struct MR_FW_RAID_MAP_ALL *map,
+			      struct LD_LOAD_BALANCE_INFO *lbInfo);
+
+u32 mega_mod64(u64 dividend, u32 divisor)
+{
+	u64 d;
+	u32 remainder;
+
+	if (!divisor)
+		printk(KERN_ERR "megasas : DIVISOR is zero, in div fn\n");
+	d = dividend;
+	remainder = do_div(d, divisor);
+	return remainder;
+}
+
+/**
+ * @param dividend    : Dividend
+ * @param divisor    : Divisor
+ *
+ * @return quotient
+ **/
+u64 mega_div64_32(uint64_t dividend, uint32_t divisor)
+{
+	u32 remainder;
+	u64 d;
+
+	if (!divisor)
+		printk(KERN_ERR "megasas : DIVISOR is zero in mod fn\n");
+
+	d = dividend;
+	remainder = do_div(d, divisor);
+
+	return d;
+}
+
+struct MR_LD_RAID *MR_LdRaidGet(u32 ld, struct MR_FW_RAID_MAP_ALL *map)
+{
+	return &map->raidMap.ldSpanMap[ld].ldRaid;
+}
+
+static struct MR_SPAN_BLOCK_INFO *MR_LdSpanInfoGet(u32 ld,
+						   struct MR_FW_RAID_MAP_ALL
+						   *map)
+{
+	return &map->raidMap.ldSpanMap[ld].spanBlock[0];
+}
+
+static u8 MR_LdDataArmGet(u32 ld, u32 armIdx, struct MR_FW_RAID_MAP_ALL *map)
+{
+	return map->raidMap.ldSpanMap[ld].dataArmMap[armIdx];
+}
+
+static u16 MR_ArPdGet(u32 ar, u32 arm, struct MR_FW_RAID_MAP_ALL *map)
+{
+	return map->raidMap.arMapInfo[ar].pd[arm];
+}
+
+static u16 MR_LdSpanArrayGet(u32 ld, u32 span, struct MR_FW_RAID_MAP_ALL *map)
+{
+	return map->raidMap.ldSpanMap[ld].spanBlock[span].span.arrayRef;
+}
+
+static u16 MR_PdDevHandleGet(u32 pd, struct MR_FW_RAID_MAP_ALL *map)
+{
+	return map->raidMap.devHndlInfo[pd].curDevHdl;
+}
+
+u16 MR_GetLDTgtId(u32 ld, struct MR_FW_RAID_MAP_ALL *map)
+{
+	return map->raidMap.ldSpanMap[ld].ldRaid.targetId;
+}
+
+u16 MR_TargetIdToLdGet(u32 ldTgtId, struct MR_FW_RAID_MAP_ALL *map)
+{
+	return map->raidMap.ldTgtIdToLd[ldTgtId];
+}
+
+static struct MR_LD_SPAN *MR_LdSpanPtrGet(u32 ld, u32 span,
+					  struct MR_FW_RAID_MAP_ALL *map)
+{
+	return &map->raidMap.ldSpanMap[ld].spanBlock[span].span;
+}
+
+/*
+ * This function will validate Map info data provided by FW
+ */
+u8 MR_ValidateMapInfo(struct MR_FW_RAID_MAP_ALL *map,
+		      struct LD_LOAD_BALANCE_INFO *lbInfo)
+{
+	struct MR_FW_RAID_MAP *pFwRaidMap = &map->raidMap;
+
+	if (pFwRaidMap->totalSize !=
+	    (sizeof(struct MR_FW_RAID_MAP) -sizeof(struct MR_LD_SPAN_MAP) +
+	     (sizeof(struct MR_LD_SPAN_MAP) *pFwRaidMap->ldCount))) {
+		printk(KERN_ERR "megasas: map info structure size 0x%x is not matching with ld count\n",
+		       (unsigned int)((sizeof(struct MR_FW_RAID_MAP) -
+				       sizeof(struct MR_LD_SPAN_MAP)) +
+				      (sizeof(struct MR_LD_SPAN_MAP) *
+				       pFwRaidMap->ldCount)));
+		printk(KERN_ERR "megasas: span map %x, pFwRaidMap->totalSize "
+		       ": %x\n", (unsigned int)sizeof(struct MR_LD_SPAN_MAP),
+		       pFwRaidMap->totalSize);
+		return 0;
+	}
+
+	mr_update_load_balance_params(map, lbInfo);
+
+	return 1;
+}
+
+u32 MR_GetSpanBlock(u32 ld, u64 row, u64 *span_blk,
+		    struct MR_FW_RAID_MAP_ALL *map, int *div_error)
+{
+	struct MR_SPAN_BLOCK_INFO *pSpanBlock = MR_LdSpanInfoGet(ld, map);
+	struct MR_QUAD_ELEMENT    *quad;
+	struct MR_LD_RAID         *raid = MR_LdRaidGet(ld, map);
+	u32                span, j;
+
+	for (span = 0; span < raid->spanDepth; span++, pSpanBlock++) {
+
+		for (j = 0; j < pSpanBlock->block_span_info.noElements; j++) {
+			quad = &pSpanBlock->block_span_info.quad[j];
+
+			if (quad->diff == 0) {
+				*div_error = 1;
+				return span;
+			}
+			if (quad->logStart <= row  &&  row <= quad->logEnd  &&
+			    (mega_mod64(row-quad->logStart, quad->diff)) == 0) {
+				if (span_blk != NULL) {
+					u64  blk, debugBlk;
+					blk =
+						mega_div64_32(
+							(row-quad->logStart),
+							quad->diff);
+					debugBlk = blk;
+
+					blk = (blk + quad->offsetInSpan) <<
+						raid->stripeShift;
+					*span_blk = blk;
+				}
+				return span;
+			}
+		}
+	}
+	return span;
+}
+
+/*
+******************************************************************************
+*
+* This routine calculates the arm, span and block for the specified stripe and
+* reference in stripe.
+*
+* Inputs :
+*
+*    ld   - Logical drive number
+*    stripRow        - Stripe number
+*    stripRef    - Reference in stripe
+*
+* Outputs :
+*
+*    span          - Span number
+*    block         - Absolute Block number in the physical disk
+*/
+u8 MR_GetPhyParams(u32 ld, u64 stripRow, u16 stripRef, u64 *pdBlock,
+		   u16 *pDevHandle, struct RAID_CONTEXT *pRAID_Context,
+		   struct MR_FW_RAID_MAP_ALL *map)
+{
+	struct MR_LD_RAID  *raid = MR_LdRaidGet(ld, map);
+	u32         pd, arRef;
+	u8          physArm, span;
+	u64         row;
+	u8	    retval = TRUE;
+	int	    error_code = 0;
+
+	row =  mega_div64_32(stripRow, raid->rowDataSize);
+
+	if (raid->level == 6) {
+		/* logical arm within row */
+		u32 logArm =  mega_mod64(stripRow, raid->rowDataSize);
+		u32 rowMod, armQ, arm;
+
+		if (raid->rowSize == 0)
+			return FALSE;
+		/* get logical row mod */
+		rowMod = mega_mod64(row, raid->rowSize);
+		armQ = raid->rowSize-1-rowMod; /* index of Q drive */
+		arm = armQ+1+logArm; /* data always logically follows Q */
+		if (arm >= raid->rowSize) /* handle wrap condition */
+			arm -= raid->rowSize;
+		physArm = (u8)arm;
+	} else  {
+		if (raid->modFactor == 0)
+			return FALSE;
+		physArm = MR_LdDataArmGet(ld,  mega_mod64(stripRow,
+							  raid->modFactor),
+					  map);
+	}
+
+	if (raid->spanDepth == 1) {
+		span = 0;
+		*pdBlock = row << raid->stripeShift;
+	} else {
+		span = (u8)MR_GetSpanBlock(ld, row, pdBlock, map, &error_code);
+		if (error_code == 1)
+			return FALSE;
+	}
+
+	/* Get the array on which this span is present */
+	arRef       = MR_LdSpanArrayGet(ld, span, map);
+	pd          = MR_ArPdGet(arRef, physArm, map); /* Get the pd */
+
+	if (pd != MR_PD_INVALID)
+		/* Get dev handle from Pd. */
+		*pDevHandle = MR_PdDevHandleGet(pd, map);
+	else {
+		*pDevHandle = MR_PD_INVALID; /* set dev handle as invalid. */
+		if (raid->level >= 5)
+			pRAID_Context->regLockFlags = REGION_TYPE_EXCLUSIVE;
+		else if (raid->level == 1) {
+			/* Get alternate Pd. */
+			pd = MR_ArPdGet(arRef, physArm + 1, map);
+			if (pd != MR_PD_INVALID)
+				/* Get dev handle from Pd */
+				*pDevHandle = MR_PdDevHandleGet(pd, map);
+		}
+		retval = FALSE;
+	}
+
+	*pdBlock += stripRef + MR_LdSpanPtrGet(ld, span, map)->startBlk;
+	pRAID_Context->spanArm = (span << RAID_CTX_SPANARM_SPAN_SHIFT) |
+		physArm;
+	return retval;
+}
+
+/*
+******************************************************************************
+*
+* MR_BuildRaidContext function
+*
+* This function will initiate command processing.  The start/end row and strip
+* information is calculated then the lock is acquired.
+* This function will return 0 if region lock was acquired OR return num strips
+*/
+u8
+MR_BuildRaidContext(struct IO_REQUEST_INFO *io_info,
+		    struct RAID_CONTEXT *pRAID_Context,
+		    struct MR_FW_RAID_MAP_ALL *map)
+{
+	struct MR_LD_RAID  *raid;
+	u32         ld, stripSize, stripe_mask;
+	u64         endLba, endStrip, endRow, start_row, start_strip;
+	u64         regStart;
+	u32         regSize;
+	u8          num_strips, numRows;
+	u16         ref_in_start_stripe, ref_in_end_stripe;
+	u64         ldStartBlock;
+	u32         numBlocks, ldTgtId;
+	u8          isRead;
+	u8	    retval = 0;
+
+	ldStartBlock = io_info->ldStartBlock;
+	numBlocks = io_info->numBlocks;
+	ldTgtId = io_info->ldTgtId;
+	isRead = io_info->isRead;
+
+	ld = MR_TargetIdToLdGet(ldTgtId, map);
+	raid = MR_LdRaidGet(ld, map);
+
+	stripSize = 1 << raid->stripeShift;
+	stripe_mask = stripSize-1;
+	/*
+	 * calculate starting row and stripe, and number of strips and rows
+	 */
+	start_strip         = ldStartBlock >> raid->stripeShift;
+	ref_in_start_stripe = (u16)(ldStartBlock & stripe_mask);
+	endLba              = ldStartBlock + numBlocks - 1;
+	ref_in_end_stripe   = (u16)(endLba & stripe_mask);
+	endStrip            = endLba >> raid->stripeShift;
+	num_strips          = (u8)(endStrip - start_strip + 1); /* End strip */
+	if (raid->rowDataSize == 0)
+		return FALSE;
+	start_row           =  mega_div64_32(start_strip, raid->rowDataSize);
+	endRow              =  mega_div64_32(endStrip, raid->rowDataSize);
+	numRows             = (u8)(endRow - start_row + 1);
+
+	/*
+	 * calculate region info.
+	 */
+
+	/* assume region is at the start of the first row */
+	regStart            = start_row << raid->stripeShift;
+	/* assume this IO needs the full row - we'll adjust if not true */
+	regSize             = stripSize;
+
+	/* If IO spans more than 1 strip, fp is not possible
+	   FP is not possible for writes on non-0 raid levels
+	   FP is not possible if LD is not capable */
+	if (num_strips > 1 || (!isRead && raid->level != 0) ||
+	    !raid->capability.fpCapable) {
+		io_info->fpOkForIo = FALSE;
+	} else {
+		io_info->fpOkForIo = TRUE;
+	}
+
+	if (numRows == 1) {
+		/* single-strip IOs can always lock only the data needed */
+		if (num_strips == 1) {
+			regStart += ref_in_start_stripe;
+			regSize = numBlocks;
+		}
+		/* multi-strip IOs always need to full stripe locked */
+	} else {
+		if (start_strip == (start_row + 1) * raid->rowDataSize - 1) {
+			/* If the start strip is the last in the start row */
+			regStart += ref_in_start_stripe;
+			regSize = stripSize - ref_in_start_stripe;
+			/* initialize count to sectors from startref to end
+			   of strip */
+		}
+
+		if (numRows > 2)
+			/* Add complete rows in the middle of the transfer */
+			regSize += (numRows-2) << raid->stripeShift;
+
+		/* if IO ends within first strip of last row */
+		if (endStrip == endRow*raid->rowDataSize)
+			regSize += ref_in_end_stripe+1;
+		else
+			regSize += stripSize;
+	}
+
+	pRAID_Context->timeoutValue     = map->raidMap.fpPdIoTimeoutSec;
+	pRAID_Context->regLockFlags     = (isRead) ? REGION_TYPE_SHARED_READ :
+		raid->regTypeReqOnWrite;
+	pRAID_Context->VirtualDiskTgtId = raid->targetId;
+	pRAID_Context->regLockRowLBA    = regStart;
+	pRAID_Context->regLockLength    = regSize;
+	pRAID_Context->configSeqNum	= raid->seqNum;
+
+	/*Get Phy Params only if FP capable, or else leave it to MR firmware
+	  to do the calculation.*/
+	if (io_info->fpOkForIo) {
+		retval = MR_GetPhyParams(ld, start_strip, ref_in_start_stripe,
+					 &io_info->pdBlock,
+					 &io_info->devHandle, pRAID_Context,
+					 map);
+		/* If IO on an invalid Pd, then FP i snot possible */
+		if (io_info->devHandle == MR_PD_INVALID)
+			io_info->fpOkForIo = FALSE;
+		return retval;
+	} else if (isRead) {
+		uint stripIdx;
+		for (stripIdx = 0; stripIdx < num_strips; stripIdx++) {
+			if (!MR_GetPhyParams(ld, start_strip + stripIdx,
+					     ref_in_start_stripe,
+					     &io_info->pdBlock,
+					     &io_info->devHandle,
+					     pRAID_Context, map))
+				return TRUE;
+		}
+	}
+	return TRUE;
+}
+
+void
+mr_update_load_balance_params(struct MR_FW_RAID_MAP_ALL *map,
+			      struct LD_LOAD_BALANCE_INFO *lbInfo)
+{
+	int ldCount;
+	u16 ld;
+	struct MR_LD_RAID *raid;
+
+	for (ldCount = 0; ldCount < MAX_LOGICAL_DRIVES; ldCount++) {
+		ld = MR_TargetIdToLdGet(ldCount, map);
+		if (ld >= MAX_LOGICAL_DRIVES) {
+			lbInfo[ldCount].loadBalanceFlag = 0;
+			continue;
+		}
+
+		raid = MR_LdRaidGet(ld, map);
+
+		/* Two drive Optimal RAID 1 */
+		if ((raid->level == 1)  &&  (raid->rowSize == 2) &&
+		    (raid->spanDepth == 1) && raid->ldState ==
+		    MR_LD_STATE_OPTIMAL) {
+			u32 pd, arRef;
+
+			lbInfo[ldCount].loadBalanceFlag = 1;
+
+			/* Get the array on which this span is present */
+			arRef = MR_LdSpanArrayGet(ld, 0, map);
+
+			/* Get the Pd */
+			pd = MR_ArPdGet(arRef, 0, map);
+			/* Get dev handle from Pd */
+			lbInfo[ldCount].raid1DevHandle[0] =
+				MR_PdDevHandleGet(pd, map);
+			/* Get the Pd */
+			pd = MR_ArPdGet(arRef, 1, map);
+
+			/* Get the dev handle from Pd */
+			lbInfo[ldCount].raid1DevHandle[1] =
+				MR_PdDevHandleGet(pd, map);
+		} else
+			lbInfo[ldCount].loadBalanceFlag = 0;
+	}
+}
+
+u8 megasas_get_best_arm(struct LD_LOAD_BALANCE_INFO *lbInfo, u8 arm, u64 block,
+			u32 count)
+{
+	u16     pend0, pend1;
+	u64     diff0, diff1;
+	u8      bestArm;
+
+	/* get the pending cmds for the data and mirror arms */
+	pend0 = atomic_read(&lbInfo->scsi_pending_cmds[0]);
+	pend1 = atomic_read(&lbInfo->scsi_pending_cmds[1]);
+
+	/* Determine the disk whose head is nearer to the req. block */
+	diff0 = ABS_DIFF(block, lbInfo->last_accessed_block[0]);
+	diff1 = ABS_DIFF(block, lbInfo->last_accessed_block[1]);
+	bestArm = (diff0 <= diff1 ? 0 : 1);
+
+	if ((bestArm == arm && pend0 > pend1 + 16)  ||
+	    (bestArm != arm && pend1 > pend0 + 16))
+		bestArm ^= 1;
+
+	/* Update the last accessed block on the correct pd */
+	lbInfo->last_accessed_block[bestArm] = block + count - 1;
+
+	return bestArm;
+}
+
+u16 get_updated_dev_handle(struct LD_LOAD_BALANCE_INFO *lbInfo,
+			   struct IO_REQUEST_INFO *io_info)
+{
+	u8 arm, old_arm;
+	u16 devHandle;
+
+	old_arm = lbInfo->raid1DevHandle[0] == io_info->devHandle ? 0 : 1;
+
+	/* get best new arm */
+	arm  = megasas_get_best_arm(lbInfo, old_arm, io_info->ldStartBlock,
+				    io_info->numBlocks);
+	devHandle = lbInfo->raid1DevHandle[arm];
+	atomic_inc(&lbInfo->scsi_pending_cmds[arm]);
+
+	return devHandle;
+}