s390: use SPARSE_IRQ

Use dynamically allocated irq descriptors on s390 which allows
us to get rid of the s390 specific config option PCI_NR_MSI and
exploit more MSI interrupts. Also the size of the kernel image
is reduced by 131K (using performance_defconfig).

Signed-off-by: Sebastian Ott <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

arch/s390/Kconfig

···
 	select NO_BOOTMEM
 	select OLD_SIGACTION
 	select OLD_SIGSUSPEND3
+	select SPARSE_IRQ
 	select SYSCTL_EXCEPTION_TRACE
 	select TTY
 	select VIRT_CPU_ACCOUNTING
···
 	help
 	  This allows you to specify the maximum number of PCI functions which
 	  this kernel will support.
-
-config PCI_NR_MSI
-	int "Maximum number of MSI interrupts (64-32768)"
-	range 64 32768
-	default "256"
-	help
-	  This defines the number of virtual interrupts the kernel will
-	  provide for MSI interrupts. If you configure your system to have
-	  too few drivers will fail to allocate MSI interrupts for all
-	  PCI devices.
 
 source "drivers/pci/Kconfig"
 

arch/s390/include/asm/irq.h

···
 
 #define NR_IRQS_BASE	3
 
-#ifdef CONFIG_PCI_NR_MSI
-# define NR_IRQS	(NR_IRQS_BASE + CONFIG_PCI_NR_MSI)
-#else
-# define NR_IRQS	NR_IRQS_BASE
-#endif
+#define NR_IRQS	NR_IRQS_BASE
+#define NR_IRQS_LEGACY NR_IRQS_BASE
 
 /* External interruption codes */
 #define EXT_IRQ_INTERRUPT_KEY	0x0040

arch/s390/kernel/irq.c

···
 			seq_printf(p, "CPU%d       ", cpu);
 		seq_putc(p, '\n');
 	}
-	if (index < NR_IRQS) {
-		if (index >= NR_IRQS_BASE)
-			goto out;
+	if (index < NR_IRQS_BASE) {
 		seq_printf(p, "%s: ", irqclass_main_desc[index].name);
 		irq = irqclass_main_desc[index].irq;
 		for_each_online_cpu(cpu)
···
 		seq_putc(p, '\n');
 		goto out;
 	}
+	if (index > NR_IRQS_BASE)
+		goto out;
+
 	for (index = 0; index < NR_ARCH_IRQS; index++) {
 		seq_printf(p, "%s: ", irqclass_sub_desc[index].name);
 		irq = irqclass_sub_desc[index].irq;