gpio: fix pca953x set_type 'scheduling while atomic' bug

Bill Gatliff reported the following bug when using the irq_chip facility
of the pca953x driver on a PPC platform:

BUG: scheduling while atomic: insmod/1530/0x00000002

He traced it back to an i2c transaction in pca953x_irq_set_type(), which
can be called with interrupt disabled (from __setup_irq()).  As the i2c
controller can sleep while sending a message, this qualifies as a bad
idea.

This patch moves the i2c transaction to pca953x_irq_bus_sync_unlock(),
where it is actually safe to send an i2c message.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Marc Zyngier <maz@misterjones.org>
Reported-by: Bill Gatliff <bgat@billgatliff.com>
Cc: Eric Miao <eric.y.miao@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 1 deletions

diff --git a/drivers/gpio/pca953x.c b/drivers/gpio/pca953x.c
index 7d521e1d17e1..b827c976dc62 100644
--- a/drivers/gpio/pca953x.c
+++ b/drivers/gpio/pca953x.c
@@ -252,6 +252,18 @@ static void pca953x_irq_bus_lock(unsigned int irq)
 static void pca953x_irq_bus_sync_unlock(unsigned int irq)
 {
         struct pca953x_chip *chip = get_irq_chip_data(irq);
+        uint16_t new_irqs;
+        uint16_t level;
+
+        /* Look for any newly setup interrupt */
+        new_irqs = chip->irq_trig_fall | chip->irq_trig_raise;
+        new_irqs &= ~chip->reg_direction;
+
+        while (new_irqs) {
+                level = __ffs(new_irqs);
+                pca953x_gpio_direction_input(&chip->gpio_chip, level);
+                new_irqs &= ~(1 << level);
+        }
 
         mutex_unlock(&chip->irq_lock);
 }
@@ -278,7 +290,7 @@ static int pca953x_irq_set_type(unsigned int irq, unsigned int type)
         else
                 chip->irq_trig_raise &= ~mask;
 
-        return pca953x_gpio_direction_input(&chip->gpio_chip, level);
+        return 0;
 }
 
 static struct irq_chip pca953x_irq_chip = {