diff --git a/drivers/serial/mpsc.c b/drivers/serial/mpsc.c
index d09f209..00924fe 100644
--- a/drivers/serial/mpsc.c
+++ b/drivers/serial/mpsc.c
@@ -503,7 +503,8 @@
 
 	if (pi->mirror_regs)
 		pi->shared_regs->SDMA_INTR_CAUSE_m = 0;
-	writel(0, pi->shared_regs->sdma_intr_base + SDMA_INTR_CAUSE);
+	writeb(0x00, pi->shared_regs->sdma_intr_base + SDMA_INTR_CAUSE +
+	       pi->port.line);
 	return;
 }