[tip:irq/urgent] irqdomain: Allow domain lookup with DOMAIN_BUS_WIRED token

[tip-bot for Marc Zyngier <tipbot@zytor.com>]

Commit-ID:  530cbe100ef7587aa5b5ac3a4b670cda4d50e598
Gitweb:     http://git.kernel.org/tip/530cbe100ef7587aa5b5ac3a4b670cda4d50e598
Author:     Marc Zyngier <marc.zyngier@arm.com>
AuthorDate: Tue, 26 Jan 2016 13:52:25 +0000
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 26 Jan 2016 16:00:14 +0100

irqdomain: Allow domain lookup with DOMAIN_BUS_WIRED token

Let's take the (outlandish) example of an interrupt controller
capable of handling both wired interrupts and PCI MSIs.

With the current code, the PCI MSI domain is going to be tagged
with DOMAIN_BUS_PCI_MSI, and the wired domain with DOMAIN_BUS_ANY.

Things get hairy when we start looking up the domain for a wired
interrupt (typically when creating it based on some firmware
information - DT or ACPI).

In irq_create_fwspec_mapping(), we perform the lookup using
DOMAIN_BUS_ANY, which is actually used as a wildcard. This gives
us one chance out of two to end up with the wrong domain, and
we try to configure a wired interrupt with the MSI domain.
Everything grinds to a halt pretty quickly.

What we really need to do is to start looking for a domain that
would uniquely identify a wired interrupt domain, and only use
DOMAIN_BUS_ANY as a fallback.

In order to solve this, let's introduce a new DOMAIN_BUS_WIRED
token, which is going to be used exactly as described above.
Of course, this depends on the irqchip to setup the domain
bus_token, and nobody had to implement this so far.

Only so far.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Link: http://lkml.kernel.org/r/1453816347-32720-2-git-send-email-marc.zyngier@arm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/irqdomain.h |  1 +
 kernel/irq/irqdomain.c    | 11 ++++++++---
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index f64622a..04579d9 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -70,6 +70,7 @@ struct irq_fwspec {
  */
 enum irq_domain_bus_token {
 	DOMAIN_BUS_ANY		= 0,
+	DOMAIN_BUS_WIRED,
 	DOMAIN_BUS_PCI_MSI,
 	DOMAIN_BUS_PLATFORM_MSI,
 	DOMAIN_BUS_NEXUS,
diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index 8cf95de..d751797 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -575,10 +575,15 @@ unsigned int irq_create_fwspec_mapping(struct irq_fwspec *fwspec)
 	unsigned int type = IRQ_TYPE_NONE;
 	int virq;
 
-	if (fwspec->fwnode)
-		domain = irq_find_matching_fwnode(fwspec->fwnode, DOMAIN_BUS_ANY);
-	else
+	if (fwspec->fwnode) {
+		domain = irq_find_matching_fwnode(fwspec->fwnode,
+						  DOMAIN_BUS_WIRED);
+		if (!domain)
+			domain = irq_find_matching_fwnode(fwspec->fwnode,
+							  DOMAIN_BUS_ANY);
+	} else {
 		domain = irq_default_domain;
+	}
 
 	if (!domain) {
 		pr_warn("no irq domain found for %s !\n",