scsi: megaraid_sas: Call disable_irq from process IRQ poll

On PowerPC architecture, calling disable_irq_nosync from IRQ context is not
providing the required effect.

In current megaraid_sas driver, disable_irq_nosync is being called from IRQ
context before enabling IRQ poll. But due to the issue seen on PPC, after
IRQ poll disable and legacy ISR is enabled, we are not seeing our ISR
getting called.

Fix: Call disable_irq from IRQ poll thread context instead of IRQ context.
Signed-off-by: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
Signed-off-by: Chandrakanth Patil <chandrakanth.patil@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/megaraid/megaraid_sas.h

@@ -2186,6 +2186,7 @@ struct megasas_irq_context {
 	u32 os_irq;
 	struct irq_poll irqpoll;
 	bool irq_poll_scheduled;
+	bool irq_line_enable;
 };
 
 struct MR_DRV_SYSTEM_INFO {

drivers/scsi/megaraid/megaraid_sas_fusion.c

@@ -3601,7 +3601,7 @@ complete_cmd_fusion(struct megasas_instance *instance, u32 MSIxIndex,
 			if (irq_context) {
 				if (!irq_context->irq_poll_scheduled) {
 					irq_context->irq_poll_scheduled = true;
-					disable_irq_nosync(irq_context->os_irq);
+					irq_context->irq_line_enable = true;
 					irq_poll_sched(&irq_context->irqpoll);
 				}
 				return num_completed;
@@ -3681,6 +3681,11 @@ int megasas_irqpoll(struct irq_poll *irqpoll, int budget)
 	irq_ctx = container_of(irqpoll, struct megasas_irq_context, irqpoll);
 	instance = irq_ctx->instance;
 
+	if (irq_ctx->irq_line_enable) {
+		disable_irq(irq_ctx->os_irq);
+		irq_ctx->irq_line_enable = false;
+	}
+
 	num_entries = complete_cmd_fusion(instance, irq_ctx->MSIxIndex, irq_ctx);
 	if (num_entries < budget) {
 		irq_poll_complete(irqpoll);
@@ -3726,6 +3731,11 @@ irqreturn_t megasas_isr_fusion(int irq, void *devp)
 	if (instance->mask_interrupts)
 		return IRQ_NONE;
 
+#if defined(ENABLE_IRQ_POLL)
+	if (irq_context->irq_poll_scheduled)
+		return IRQ_HANDLED;
+#endif
+
 	if (!instance->msix_vectors) {
 		mfiStatus = instance->instancet->clear_intr(instance);
 		if (!mfiStatus)