gpio: timbgpio: use a copy of the IER register to avoid it being trashed
authorTomas Hallenberg <tomas.hallenberg@pelagicore.com>
Wed, 27 Oct 2010 22:33:17 +0000 (15:33 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 28 Oct 2010 01:03:07 +0000 (18:03 -0700)
Some versions of the hardware can trash the IER register if simultaneous
interrupts occur.  This patch works around it by using a local copy of the
register and restoring it after every interrupt.

Signed-off-by: Tomas Hallenberg <tomas.hallenberg@pelagicore.com>
Acked-by: Richard Röjfors <richard.rojfors@pelagicore.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
drivers/gpio/timbgpio.c

index ddd053108a136ce2a41dd346a438622609c7f480..45293662e95045594c2a9ed12ece640c2590f93f 100644 (file)
@@ -47,6 +47,7 @@ struct timbgpio {
        spinlock_t              lock; /* mutual exclusion */
        struct gpio_chip        gpio;
        int                     irq_base;
+       unsigned long           last_ier;
 };
 
 static int timbgpio_update_bit(struct gpio_chip *gpio, unsigned index,
@@ -112,16 +113,24 @@ static void timbgpio_irq_disable(unsigned irq)
 {
        struct timbgpio *tgpio = get_irq_chip_data(irq);
        int offset = irq - tgpio->irq_base;
+       unsigned long flags;
 
-       timbgpio_update_bit(&tgpio->gpio, offset, TGPIO_IER, 0);
+       spin_lock_irqsave(&tgpio->lock, flags);
+       tgpio->last_ier &= ~(1 << offset);
+       iowrite32(tgpio->last_ier, tgpio->membase + TGPIO_IER);
+       spin_unlock_irqrestore(&tgpio->lock, flags);
 }
 
 static void timbgpio_irq_enable(unsigned irq)
 {
        struct timbgpio *tgpio = get_irq_chip_data(irq);
        int offset = irq - tgpio->irq_base;
+       unsigned long flags;
 
-       timbgpio_update_bit(&tgpio->gpio, offset, TGPIO_IER, 1);
+       spin_lock_irqsave(&tgpio->lock, flags);
+       tgpio->last_ier |= 1 << offset;
+       iowrite32(tgpio->last_ier, tgpio->membase + TGPIO_IER);
+       spin_unlock_irqrestore(&tgpio->lock, flags);
 }
 
 static int timbgpio_irq_type(unsigned irq, unsigned trigger)
@@ -194,8 +203,16 @@ static void timbgpio_irq(unsigned int irq, struct irq_desc *desc)
        ipr = ioread32(tgpio->membase + TGPIO_IPR);
        iowrite32(ipr, tgpio->membase + TGPIO_ICR);
 
+       /*
+        * Some versions of the hardware trash the IER register if more than
+        * one interrupt is received simultaneously.
+        */
+       iowrite32(0, tgpio->membase + TGPIO_IER);
+
        for_each_set_bit(offset, &ipr, tgpio->gpio.ngpio)
                generic_handle_irq(timbgpio_to_irq(&tgpio->gpio, offset));
+
+       iowrite32(tgpio->last_ier, tgpio->membase + TGPIO_IER);
 }
 
 static struct irq_chip timbgpio_irqchip = {