gpiolib: avoid sleeping lock from atomic context in gpiochip_add

If GPIO device is added from device tree then gpiochip_add() try
to find the aliased base for that device on atomic context.
The of_alias_get_id() is sleeping calls, so it dumps warning of
sleeping calls from atomic context as:
--
[    6.320139] BUG: sleeping function called from invalid context at kernel/kernel/mutex.c:413
[    6.332406] in_atomic(): 1, irqs_disabled(): 128, pid: 1, name: swapper/0
[    6.339157] INFO: lockdep is turned off.
[    6.343058] irq event stamp: 106315
[    6.346523] hardirqs last  enabled at (106315): [<ffffffc0000a6724>] vprintk_emit+0x1ac/0x57c
[    6.355017] hardirqs last disabled at (106314): [<ffffffc0000a65c8>] vprintk_emit+0x50/0x57c
[    6.363423] softirqs last  enabled at (105022): [<ffffffc0000ac730>] __do_softirq+0x1b8/0x2c0
[    6.371917] softirqs last disabled at (105017): [<ffffffc0000ac91c>] do_softirq+0x6c/0x84
[    6.380074] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G        W    3.10.33-g60742c9-dirty #47
[    6.388385] Call trace:
[    6.390818] [<ffffffc0000885f4>] dump_backtrace+0x0/0x16c
[    6.396192] [<ffffffc000088770>] show_stack+0x10/0x1c
[    6.401218] [<ffffffc000956a30>] dump_stack+0x1c/0x28
[    6.406243] [<ffffffc0000d604c>] __might_sleep+0x118/0x120
[    6.411703] [<ffffffc00095b788>] mutex_lock_nested+0x40/0x350
[    6.417424] [<ffffffc0006d05f8>] of_alias_get_id+0x2c/0x94
[    6.422891] [<ffffffc000350170>] gpiochip_add+0x1b8/0x3f0
[    6.428255] [<ffffffc0003531dc>] pca953x_probe+0x214/0x4fc
----

Rewrite this piece of code such that of_alias_get_id() will get called
from non-atomic context to avoid above bug.

Change-Id: I0c003f9fbec9661acaa3c5e41c4bc90f6d50729f
Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Reviewed-on: http://git-master/r/396957
Reviewed-by: Thomas Cherry <tcherry@nvidia.com>
GVS: Gerrit_Virtual_Submit

1 files changed, 22 insertions, 22 deletions

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 0e6c9bd34f53..92e03d478dd5 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -184,37 +184,31 @@ struct gpio_chip *gpio_to_chip(unsigned gpio)
 }
 
 /* dynamic allocation of GPIOs, e.g. on a hotplugged device */
-static int gpiochip_find_base(struct gpio_chip *req_chip)
+static int gpiochip_find_base(struct gpio_chip *req_chip, int aliased_base)
 {
 	struct gpio_chip *chip;
 	int ngpio = req_chip->ngpio;
 	int base = -1;
 
-#ifdef CONFIG_OF
-	if (req_chip->of_node) {
-		int gpio_nr;
+	if (aliased_base >= 0) {
+		int start_gpio = aliased_base;
+		int end_gpio = aliased_base + req_chip->ngpio;
 
-		gpio_nr = of_alias_get_id(req_chip->of_node, "gpio");
-		if (gpio_nr >= 0) {
-			int start_gpio = gpio_nr;
-			int end_gpio = gpio_nr + req_chip->ngpio;
+		/* Check if aliased base is not already allocated */
+		list_for_each_entry(chip, &gpio_chips, list) {
+			if (chip->base > end_gpio)
+				continue;
 
-			list_for_each_entry(chip, &gpio_chips, list) {
-				if (chip->base > end_gpio)
+			if ((chip->base < start_gpio) &&
+				((chip->base + chip->ngpio) < start_gpio))
 					continue;
-
-				if ((chip->base < start_gpio) &&
-					((chip->base + chip->ngpio) < start_gpio))
-						continue;
-				pr_err("GPIO %d to %d is already allocated\n",
-						start_gpio, end_gpio);
-				gpio_nr = -1;
-				break;
-			}
+			pr_err("GPIO %d to %d is already allocated\n",
+					start_gpio, end_gpio);
+			aliased_base = -1;
+			break;
 		}
-		base = gpio_nr;
+		base = aliased_base;
 	}
-#endif
 
 	if (base >= 0)
 		goto found;
@@ -1206,6 +1200,7 @@ int gpiochip_add(struct gpio_chip *chip)
 	int		status = 0;
 	unsigned	id;
 	int		base = chip->base;
+	int		aliased_base = -1;
 
 	if ((!gpio_is_valid(base) || !gpio_is_valid(base + chip->ngpio - 1))
 			&& base >= 0) {
@@ -1213,10 +1208,15 @@ int gpiochip_add(struct gpio_chip *chip)
 		goto fail;
 	}
 
+#ifdef CONFIG_OF
+	if (chip->of_node)
+		aliased_base = of_alias_get_id(chip->of_node, "gpio");
+#endif
+
 	spin_lock_irqsave(&gpio_lock, flags);
 
 	if (base < 0) {
-		base = gpiochip_find_base(chip);
+		base = gpiochip_find_base(chip, aliased_base);
 		if (base < 0) {
 			status = base;
 			goto unlock;