[POWERPC] Export virq mapping via debugfs

This adds a debugfs file "powerpc/virq_mapping", which shows the virtual
to real mapping of irq numbers.  Enable it with CONFIG_VIRQ_DEBUG.

Signed-off-by: Zhang Wei <wei.zhang@freescale.com>
Signed-off-by: Chen Gong <G.Chen@freescale.com>
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

2 files changed, 73 insertions, 0 deletions

diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
index 22acece95b11..c38bc2237057 100644
--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug
@@ -124,6 +124,16 @@ config IRQSTACKS
           for handling hard and soft interrupts.  This can help avoid
           overflowing the process kernel stacks.
 
+config VIRQ_DEBUG
+        bool "Expose hardware/virtual IRQ mapping via debugfs"
+        depends on DEBUG_FS && PPC_MERGE
+        help
+          This option will show the mapping relationship between hardware irq
+          numbers and virtual irq numbers. The mapping is exposed via debugfs
+          in the file powerpc/virq_mapping.
+
+          If you don't know what this means you don't need it.
+
 config BDI_SWITCH
         bool "Include BDI-2000 user context switcher"
         depends on DEBUG_KERNEL && PPC32
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 1339f32b44b5..0e47c8cfc979 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -52,6 +52,7 @@
 #include <linux/mutex.h>
 #include <linux/bootmem.h>
 #include <linux/pci.h>
+#include <linux/debugfs.h>
 
 #include <asm/uaccess.h>
 #include <asm/system.h>
@@ -1006,6 +1007,68 @@ static int irq_late_init(void)
 }
 arch_initcall(irq_late_init);
 
+#ifdef CONFIG_VIRQ_DEBUG
+static int virq_debug_show(struct seq_file *m, void *private)
+{
+        unsigned long flags;
+        irq_desc_t *desc;
+        const char *p;
+        char none[] = "none";
+        int i;
+
+        seq_printf(m, "%-5s  %-7s  %-15s  %s\n", "virq", "hwirq",
+                      "chip name", "host name");
+
+        for (i = 1; i < NR_IRQS; i++) {
+                desc = get_irq_desc(i);
+                spin_lock_irqsave(&desc->lock, flags);
+
+                if (desc->action && desc->action->handler) {
+                        seq_printf(m, "%5d  ", i);
+                        seq_printf(m, "0x%05lx  ", virq_to_hw(i));
+
+                        if (desc->chip && desc->chip->typename)
+                                p = desc->chip->typename;
+                        else
+                                p = none;
+                        seq_printf(m, "%-15s  ", p);
+
+                        if (irq_map[i].host && irq_map[i].host->of_node)
+                                p = irq_map[i].host->of_node->full_name;
+                        else
+                                p = none;
+                        seq_printf(m, "%s\n", p);
+                }
+
+                spin_unlock_irqrestore(&desc->lock, flags);
+        }
+
+        return 0;
+}
+
+static int virq_debug_open(struct inode *inode, struct file *file)
+{
+        return single_open(file, virq_debug_show, inode->i_private);
+}
+
+static const struct file_operations virq_debug_fops = {
+        .open = virq_debug_open,
+        .read = seq_read,
+        .llseek = seq_lseek,
+        .release = single_release,
+};
+
+static int __init irq_debugfs_init(void)
+{
+        if (debugfs_create_file("virq_mapping", S_IRUGO, powerpc_debugfs_root,
+                                 NULL, &virq_debug_fops))
+                return -ENOMEM;
+
+        return 0;
+}
+__initcall(irq_debugfs_init);
+#endif /* CONFIG_VIRQ_DEBUG */
+
 #endif /* CONFIG_PPC_MERGE */
 
 #ifdef CONFIG_PPC64