s390/pci: add parameter to force floating irqs

Provide a kernel parameter to force the usage of floating interrupts.
Signed-off-by: Sebastian Ott <sebott@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

Documentation/admin-guide/kernel-parameters.txt

@@ -3394,6 +3394,7 @@
 				bridges without forcing it upstream. Note:
 				this removes isolation between devices and
 				may put more devices in an IOMMU group.
+		force_floating	[S390] Force usage of floating interrupts.
 
 	pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
 			Management.

arch/s390/include/asm/pci.h

@@ -163,6 +163,7 @@ static inline bool zdev_enabled(struct zpci_dev *zdev)
 }
 
 extern const struct attribute_group *zpci_attr_groups[];
+extern unsigned int s390_pci_force_floating __initdata;
 
 /* -----------------------------------------------------------------------------
   Prototypes

arch/s390/pci/pci.c

@@ -741,6 +741,7 @@ static void zpci_mem_exit(void)
 }
 
 static unsigned int s390_pci_probe __initdata = 1;
+unsigned int s390_pci_force_floating __initdata;
 static unsigned int s390_pci_initialized;
 
 char * __init pcibios_setup(char *str)
@@ -749,6 +750,10 @@ char * __init pcibios_setup(char *str)
 		s390_pci_probe = 0;
 		return NULL;
 	}
+	if (!strcmp(str, "force_floating")) {
+		s390_pci_force_floating = 1;
+		return NULL;
+	}
 	return str;
 }
 

arch/s390/pci/pci_irq.c

@@ -433,6 +433,9 @@ int __init zpci_irq_init(void)
 	int rc;
 
 	irq_delivery = sclp.has_dirq ? DIRECTED : FLOATING;
+	if (s390_pci_force_floating)
+		irq_delivery = FLOATING;
+
 	if (irq_delivery == DIRECTED)
 		zpci_airq.handler = zpci_directed_irq_handler;