linux-kernel - [PATCH V3 05/16] irqchip: crossbar: change allocation logic by reversing search for free irqs

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Message-ID: <1402917796-31574-6-git-send-email-r.sricharan@ti.com>
Date:	Mon, 16 Jun 2014 16:53:05 +0530
From:	Sricharan R <r.sricharan@...com>
To:	<linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:	<tony@...mide.com>, <santosh.shilimkar@...com>, <nm@...com>,
	<rnayak@...com>, <linux@....linux.org.uk>, <r.sricharan@...com>,
	<tglx@...utronix.de>, <jason@...edaemon.net>, <joe@...ches.com>
Subject: [PATCH V3 05/16] irqchip: crossbar: change allocation logic by reversing search for free irqs

From: Nishanth Menon <nm@...com>

Reverse the search algorithm to ensure that address mapping and IRQ
allocation logics are proper. This makes the below bugs visible sooner.

class 1. address space errors -> example:
reg = <a size_b>
ti,max-irqs =  is a wrong parameter

class 2: irq-reserved list - which decides which entries in the
address space is not actually wired in

class 3: wrong list of routable-irqs.

In general allocating from max to min tends to have benefits in
ensuring the different issues that may be present in dts is easily
caught at definition time, rather than at a later point in time.

Signed-off-by: Nishanth Menon <nm@...com>
Signed-off-by: Sricharan R <r.sricharan@...com>
---
[V3] Added more description to commit log.

 drivers/irqchip/irq-crossbar.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/irqchip/irq-crossbar.c b/drivers/irqchip/irq-crossbar.c
index d1f67f6..9528cf2 100644
--- a/drivers/irqchip/irq-crossbar.c
+++ b/drivers/irqchip/irq-crossbar.c
@@ -58,7 +58,7 @@ static inline int get_prev_map_irq(int cb_no)
 {
 	int i;
 
-	for (i = 0; i < cb->int_max; i++)
+	for (i = cb->int_max - 1; i >= 0; i--)
 		if (cb->irq_map[i] == cb_no)
 			return i;
 
@@ -69,7 +69,7 @@ static inline int allocate_free_irq(int cb_no)
 {
 	int i;
 
-	for (i = 0; i < cb->int_max; i++) {
+	for (i = cb->int_max - 1; i >= 0; i--) {
 		if (cb->irq_map[i] == IRQ_FREE) {
 			cb->irq_map[i] = cb_no;
 			return i;
-- 
1.7.9.5

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