cxl: Introduce implementation-specific API

The backend API (in cxl.h) lists some low-level functions whose
implementation is different on bare-metal and in a guest. Each
environment implements its own functions, and the common code uses
them through function pointers, defined in cxl_backend_ops

Co-authored-by: Christophe Lombard <clombard@linux.vnet.ibm.com>
Signed-off-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Christophe Lombard <clombard@linux.vnet.ibm.com>
Reviewed-by: Manoj Kumar <manoj@linux.vnet.ibm.com>
Acked-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/drivers/misc/cxl/irq.c b/drivers/misc/cxl/irq.c
index 16fd67f..56ad301 100644
--- a/drivers/misc/cxl/irq.c
+++ b/drivers/misc/cxl/irq.c
@@ -79,7 +79,8 @@
 	if (dsisr & CXL_PSL_DSISR_An_UR)
 		pr_devel("CXL interrupt: AURP PTE not found\n");
 	if (dsisr & CXL_PSL_DSISR_An_PE)
-		return handle_psl_slice_error(ctx, dsisr, irq_info->errstat);
+		return cxl_ops->handle_psl_slice_error(ctx, dsisr,
+						irq_info->errstat);
 	if (dsisr & CXL_PSL_DSISR_An_AE) {
 		pr_devel("CXL interrupt: AFU Error 0x%016llx\n", irq_info->afu_err);
 
@@ -103,7 +104,7 @@
 			wake_up_all(&ctx->wq);
 		}
 
-		cxl_ack_irq(ctx, CXL_PSL_TFC_An_A, 0);
+		cxl_ops->ack_irq(ctx, CXL_PSL_TFC_An_A, 0);
 		return IRQ_HANDLED;
 	}
 	if (dsisr & CXL_PSL_DSISR_An_OC)
@@ -167,7 +168,8 @@
 		return 0;
 	}
 
-	cxl_setup_irq(adapter, hwirq, virq);
+	if (cxl_ops->setup_irq)
+		cxl_ops->setup_irq(adapter, hwirq, virq);
 
 	pr_devel("hwirq %#lx mapped to virq %u\n", hwirq, virq);
 
@@ -195,7 +197,7 @@
 {
 	int hwirq, virq;
 
-	if ((hwirq = cxl_alloc_one_irq(adapter)) < 0)
+	if ((hwirq = cxl_ops->alloc_one_irq(adapter)) < 0)
 		return hwirq;
 
 	if (!(virq = cxl_map_irq(adapter, hwirq, handler, cookie, name)))
@@ -207,7 +209,7 @@
 	return 0;
 
 err:
-	cxl_release_one_irq(adapter, hwirq);
+	cxl_ops->release_one_irq(adapter, hwirq);
 	return -ENOMEM;
 }
 
@@ -230,7 +232,8 @@
 	/* Initialize the list head to hold irq names */
 	INIT_LIST_HEAD(&ctx->irq_names);
 
-	if ((rc = cxl_alloc_irq_ranges(&ctx->irqs, ctx->afu->adapter, count)))
+	if ((rc = cxl_ops->alloc_irq_ranges(&ctx->irqs, ctx->afu->adapter,
+							count)))
 		return rc;
 
 	/* Multiplexed PSL Interrupt */
@@ -268,7 +271,7 @@
 	return 0;
 
 out:
-	cxl_release_irq_ranges(&ctx->irqs, ctx->afu->adapter);
+	cxl_ops->release_irq_ranges(&ctx->irqs, ctx->afu->adapter);
 	afu_irq_name_free(ctx);
 	return -ENOMEM;
 }
@@ -319,7 +322,7 @@
 	}
 
 	afu_irq_name_free(ctx);
-	cxl_release_irq_ranges(&ctx->irqs, ctx->afu->adapter);
+	cxl_ops->release_irq_ranges(&ctx->irqs, ctx->afu->adapter);
 
 	ctx->irq_count = 0;
 }