[ARM] pxa/dma: optimize irq handler loop

Reduce loop for dma irq handler callbacks to the minimum
required.

Since V1: included suggestion from Nicolas Pitre to improve
even further the loop.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>

1 files changed, 15 insertions, 14 deletions

diff --git a/arch/arm/plat-pxa/dma.c b/arch/arm/plat-pxa/dma.c
index 897663dbc5f4..56b51cf0718b 100644
--- a/arch/arm/plat-pxa/dma.c
+++ b/arch/arm/plat-pxa/dma.c
@@ -94,20 +94,21 @@ EXPORT_SYMBOL(pxa_free_dma);
 static irqreturn_t dma_irq_handler(int irq, void *dev_id)
 {
         int i, dint = DINT;
-
-        for (i = 0; i < num_dma_channels; i++) {
-                if (dint & (1 << i)) {
-                        struct dma_channel *channel = &dma_channels[i];
-                        if (channel->name && channel->irq_handler) {
-                                channel->irq_handler(i, channel->data);
-                        } else {
-                                /*
-                                 * IRQ for an unregistered DMA channel:
-                                 * let's clear the interrupts and disable it.
-                                 */
-                                printk (KERN_WARNING "spurious IRQ for DMA channel %d\n", i);
-                                DCSR(i) = DCSR_STARTINTR|DCSR_ENDINTR|DCSR_BUSERR;
-                        }
+        struct dma_channel *channel;
+
+        while (dint) {
+                i = __ffs(dint);
+                dint &= (dint - 1);
+                channel = &dma_channels[i];
+                if (channel->name && channel->irq_handler) {
+                        channel->irq_handler(i, channel->data);
+                } else {
+                        /*
+                         * IRQ for an unregistered DMA channel:
+                         * let's clear the interrupts and disable it.
+                         */
+                        printk (KERN_WARNING "spurious IRQ for DMA channel %d\n", i);
+                        DCSR(i) = DCSR_STARTINTR|DCSR_ENDINTR|DCSR_BUSERR;
                 }
         }
         return IRQ_HANDLED;