powerpc/512x: fix the hanged dma transfer issue

Current code clears interrupt active status _after_ submitting new
transfers. This leaves a possibility of clearing the interrupt for this
new transfer (if it is triggered fast enough) and thus lose this
interrupt. We want to clear interrupt active status _before_ new
transfers is submitted and for current channel only.

Signed-off-by: Ilya Yanok <yanok@emcraft.com>
Acked-by: Wolfgang Denk <wd@denx.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/dma/mpc512x_dma.c

@@ -276,6 +276,9 @@ static void mpc_dma_irq_process(struct mpc_dma *mdma, u32 is, u32 es, int off)
 
 		spin_lock(&mchan->lock);
 
+		out_8(&mdma->regs->dmacint, ch + off);
+		out_8(&mdma->regs->dmacerr, ch + off);
+
 		/* Check error status */
 		if (es & (1 << ch))
 			list_for_each_entry(mdesc, &mchan->active, node)
@@ -309,12 +312,6 @@ static irqreturn_t mpc_dma_irq(int irq, void *data)
 	mpc_dma_irq_process(mdma, in_be32(&mdma->regs->dmaintl),
 					in_be32(&mdma->regs->dmaerrl), 0);
 
-	/* Ack interrupt on all channels */
-	out_be32(&mdma->regs->dmainth, 0xFFFFFFFF);
-	out_be32(&mdma->regs->dmaintl, 0xFFFFFFFF);
-	out_be32(&mdma->regs->dmaerrh, 0xFFFFFFFF);
-	out_be32(&mdma->regs->dmaerrl, 0xFFFFFFFF);
-
 	/* Schedule tasklet */
 	tasklet_schedule(&mdma->tasklet);