megaraid_sas: reduce memory footprints in kdump mode

This patch will reduce memory footprints of megaraid_sas driver when
booted in kdump mode.  Driver will not allocate memory for optional and
perfromance oriented features.  Below are key changes done in
megaraid_sas driver to do this:

1. Limit Controller's queue depth to 100 in kdump mode.

2. Do not allocate memory for system info buffer and PD info buffer.

3. Disable performance oriented features e.g. Disable RDPQ mode, disable
   dual queue depth, restrict to single MSI-x vector.
Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com>
Reviewed-by: Hannes Reinicke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/megaraid/megaraid_sas.h

@@ -1344,6 +1344,8 @@ struct megasas_ctrl_info {
 #define SCAN_PD_CHANNEL	0x1
 #define SCAN_VD_CHANNEL	0x2
 
+#define MEGASAS_KDUMP_QUEUE_DEPTH               100
+
 enum MR_SCSI_CMD_TYPE {
 	READ_WRITE_LDIO = 0,
 	NON_READ_WRITE_LDIO = 1,

drivers/scsi/megaraid/megaraid_sas_base.c

@@ -5761,13 +5761,6 @@ static int megasas_probe_one(struct pci_dev *pdev,
 		break;
 	}
 
-	instance->system_info_buf = pci_zalloc_consistent(pdev,
-					sizeof(struct MR_DRV_SYSTEM_INFO),
-					&instance->system_info_h);
-
-	if (!instance->system_info_buf)
-		dev_info(&instance->pdev->dev, "Can't allocate system info buffer\n");
-
 	/* Crash dump feature related initialisation*/
 	instance->drv_buf_index = 0;
 	instance->drv_buf_alloc = 0;
@@ -5777,14 +5770,6 @@ static int megasas_probe_one(struct pci_dev *pdev,
 	spin_lock_init(&instance->crashdump_lock);
 	instance->crash_dump_buf = NULL;
 
-	if (!reset_devices)
-		instance->crash_dump_buf = pci_alloc_consistent(pdev,
-						CRASH_DMA_BUF_SIZE,
-						&instance->crash_dump_h);
-	if (!instance->crash_dump_buf)
-		dev_err(&pdev->dev, "Can't allocate Firmware "
-			"crash dump DMA buffer\n");
-
 	megasas_poll_wait_aen = 0;
 	instance->flag_ieee = 0;
 	instance->ev = NULL;
@@ -5803,11 +5788,26 @@ static int megasas_probe_one(struct pci_dev *pdev,
 		goto fail_alloc_dma_buf;
 	}
 
-	instance->pd_info = pci_alloc_consistent(pdev,
-		sizeof(struct MR_PD_INFO), &instance->pd_info_h);
+	if (!reset_devices) {
+		instance->system_info_buf = pci_zalloc_consistent(pdev,
+					sizeof(struct MR_DRV_SYSTEM_INFO),
+					&instance->system_info_h);
+		if (!instance->system_info_buf)
+			dev_info(&instance->pdev->dev, "Can't allocate system info buffer\n");
+
+		instance->pd_info = pci_alloc_consistent(pdev,
+			sizeof(struct MR_PD_INFO), &instance->pd_info_h);
 
-	if (!instance->pd_info)
-		dev_err(&instance->pdev->dev, "Failed to alloc mem for pd_info\n");
+		if (!instance->pd_info)
+			dev_err(&instance->pdev->dev, "Failed to alloc mem for pd_info\n");
+
+		instance->crash_dump_buf = pci_alloc_consistent(pdev,
+						CRASH_DMA_BUF_SIZE,
+						&instance->crash_dump_h);
+		if (!instance->crash_dump_buf)
+			dev_err(&pdev->dev, "Can't allocate Firmware "
+				"crash dump DMA buffer\n");
+	}
 
 	/*
 	 * Initialize locks and queues
@@ -7173,6 +7173,16 @@ static int __init megasas_init(void)
 {
 	int rval;
 
+	/*
+	 * Booted in kdump kernel, minimize memory footprints by
+	 * disabling few features
+	 */
+	if (reset_devices) {
+		msix_vectors = 1;
+		rdpq_enable = 0;
+		dual_qdepth_disable = 1;
+	}
+
 	/*
 	 * Announce driver version and other information
 	 */

drivers/scsi/megaraid/megaraid_sas_fusion.c

@@ -257,6 +257,9 @@ megasas_fusion_update_can_queue(struct megasas_instance *instance, int fw_boot_c
 		if (!instance->is_rdpq)
 			instance->max_fw_cmds = min_t(u16, instance->max_fw_cmds, 1024);
 
+		if (reset_devices)
+			instance->max_fw_cmds = min(instance->max_fw_cmds,
+						(u16)MEGASAS_KDUMP_QUEUE_DEPTH);
 		/*
 		* Reduce the max supported cmds by 1. This is to ensure that the
 		* reply_q_sz (1 more than the max cmd that driver may send)