genirq/debugfs: Add proper debugfs interface

Debugging (hierarchical) interupt domains is tedious as there is no
information about the hierarchy and no information about states of
interrupts in the various domain levels.

Add a debugfs directory 'irq' and subdirectories 'domains' and 'irqs'.

The domains directory contains the domain files. The content is information
about the domain. If the domain is part of a hierarchy then the parent
domains are printed as well.

# ls /sys/kernel/debug/irq/domains/
default     INTEL-IR-2	    INTEL-IR-MSI-2  IO-APIC-IR-2  PCI-MSI
DMAR-MSI    INTEL-IR-3	    INTEL-IR-MSI-3  IO-APIC-IR-3  unknown-1
INTEL-IR-0  INTEL-IR-MSI-0  IO-APIC-IR-0    IO-APIC-IR-4  VECTOR
INTEL-IR-1  INTEL-IR-MSI-1  IO-APIC-IR-1    PCI-HT

# cat /sys/kernel/debug/irq/domains/VECTOR 
name:   VECTOR
 size:   0
 mapped: 216
 flags:  0x00000041

# cat /sys/kernel/debug/irq/domains/IO-APIC-IR-0 
name:   IO-APIC-IR-0
 size:   24
 mapped: 19
 flags:  0x00000041
 parent: INTEL-IR-3
    name:   INTEL-IR-3
     size:   65536
     mapped: 167
     flags:  0x00000041
     parent: VECTOR
        name:   VECTOR
         size:   0
         mapped: 216
         flags:  0x00000041

Unfortunately there is no per cpu information about the VECTOR domain (yet).

The irqs directory contains detailed information about mapped interrupts.

# cat /sys/kernel/debug/irq/irqs/3
handler:  handle_edge_irq
status:   0x00004000
istate:   0x00000000
ddepth:   1
wdepth:   0
dstate:   0x01018000
            IRQD_IRQ_DISABLED
            IRQD_SINGLE_TARGET
            IRQD_MOVE_PCNTXT
node:     0
affinity: 0-143
effectiv: 0
pending:  
domain:  IO-APIC-IR-0
 hwirq:   0x3
 chip:    IR-IO-APIC
  flags:   0x10
             IRQCHIP_SKIP_SET_WAKE
 parent:
    domain:  INTEL-IR-3
     hwirq:   0x20000
     chip:    INTEL-IR
      flags:   0x0
     parent:
        domain:  VECTOR
         hwirq:   0x3
         chip:    APIC
          flags:   0x0

This was developed to simplify the debugging of the managed affinity
changes.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Link: http://lkml.kernel.org/r/20170619235444.537566163@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 86 insertions, 1 deletions

diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index 8d5805c655b6..75e1f0851c33 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -29,9 +29,17 @@ struct irqchip_fwid {
 	struct fwnode_handle	fwnode;
 	unsigned int		type;
 	char			*name;
-	void			*data;
+	void *data;
 };
 
+#ifdef CONFIG_GENERIC_IRQ_DEBUGFS
+static void debugfs_add_domain_dir(struct irq_domain *d);
+static void debugfs_remove_domain_dir(struct irq_domain *d);
+#else
+static inline void debugfs_add_domain_dir(struct irq_domain *d) { }
+static inline void debugfs_remove_domain_dir(struct irq_domain *d) { }
+#endif
+
 /**
  * irq_domain_alloc_fwnode - Allocate a fwnode_handle suitable for
  *                           identifying an irq domain
@@ -194,6 +202,7 @@ struct irq_domain *__irq_domain_add(struct fwnode_handle *fwnode, int size,
 	irq_domain_check_hierarchy(domain);
 
 	mutex_lock(&irq_domain_mutex);
+	debugfs_add_domain_dir(domain);
 	list_add(&domain->link, &irq_domain_list);
 	mutex_unlock(&irq_domain_mutex);
 
@@ -213,6 +222,7 @@ EXPORT_SYMBOL_GPL(__irq_domain_add);
 void irq_domain_remove(struct irq_domain *domain)
 {
 	mutex_lock(&irq_domain_mutex);
+	debugfs_remove_domain_dir(domain);
 
 	WARN_ON(!radix_tree_empty(&domain->revmap_tree));
 
@@ -1599,3 +1609,78 @@ static void irq_domain_check_hierarchy(struct irq_domain *domain)
 {
 }
 #endif	/* CONFIG_IRQ_DOMAIN_HIERARCHY */
+
+#ifdef CONFIG_GENERIC_IRQ_DEBUGFS
+static struct dentry *domain_dir;
+
+static void
+irq_domain_debug_show_one(struct seq_file *m, struct irq_domain *d, int ind)
+{
+	seq_printf(m, "%*sname:   %s\n", ind, "", d->name);
+	seq_printf(m, "%*ssize:   %u\n", ind + 1, "",
+		   d->revmap_size + d->revmap_direct_max_irq);
+	seq_printf(m, "%*smapped: %u\n", ind + 1, "", d->mapcount);
+	seq_printf(m, "%*sflags:  0x%08x\n", ind +1 , "", d->flags);
+#ifdef	CONFIG_IRQ_DOMAIN_HIERARCHY
+	if (!d->parent)
+		return;
+	seq_printf(m, "%*sparent: %s\n", ind + 1, "", d->parent->name);
+	irq_domain_debug_show_one(m, d->parent, ind + 4);
+#endif
+}
+
+static int irq_domain_debug_show(struct seq_file *m, void *p)
+{
+	struct irq_domain *d = m->private;
+
+	/* Default domain? Might be NULL */
+	if (!d) {
+		if (!irq_default_domain)
+			return 0;
+		d = irq_default_domain;
+	}
+	irq_domain_debug_show_one(m, d, 0);
+	return 0;
+}
+
+static int irq_domain_debug_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, irq_domain_debug_show, inode->i_private);
+}
+
+static const struct file_operations dfs_domain_ops = {
+	.open		= irq_domain_debug_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+static void debugfs_add_domain_dir(struct irq_domain *d)
+{
+	if (!d->name || !domain_dir || d->debugfs_file)
+		return;
+	d->debugfs_file = debugfs_create_file(d->name, 0444, domain_dir, d,
+					      &dfs_domain_ops);
+}
+
+static void debugfs_remove_domain_dir(struct irq_domain *d)
+{
+	if (d->debugfs_file)
+		debugfs_remove(d->debugfs_file);
+}
+
+void __init irq_domain_debugfs_init(struct dentry *root)
+{
+	struct irq_domain *d;
+
+	domain_dir = debugfs_create_dir("domains", root);
+	if (!domain_dir)
+		return;
+
+	debugfs_create_file("default", 0444, domain_dir, NULL, &dfs_domain_ops);
+	mutex_lock(&irq_domain_mutex);
+	list_for_each_entry(d, &irq_domain_list, link)
+		debugfs_add_domain_dir(d);
+	mutex_unlock(&irq_domain_mutex);
+}
+#endif