pch_uart: Support modem status interrupt

Signed-off-by: Tomoya MORINAGA <tomoya.rohm@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 13 insertions, 2 deletions

diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
index d035f8ff913..d11096c8ca8 100644
--- a/drivers/tty/serial/pch_uart.c
+++ b/drivers/tty/serial/pch_uart.c
@@ -1043,10 +1043,15 @@ static irqreturn_t pch_uart_interrupt(int irq, void *dev_id)
         int ret = 0;
         unsigned char iid;
         unsigned long flags;
+        int next = 1;
+        u8 msr;
 
         spin_lock_irqsave(&priv->port.lock, flags);
         handled = 0;
-        while ((iid = pch_uart_hal_get_iid(priv)) > 1) {
+        while (next) {
+                iid = pch_uart_hal_get_iid(priv);
+                if (iid & PCH_UART_IIR_IP) /* No Interrupt */
+                        break;
                 switch (iid) {
                 case PCH_UART_IID_RLS:  /* Receiver Line Status */
                         lsr = pch_uart_hal_get_line_status(priv);
@@ -1080,12 +1085,18 @@ static irqreturn_t pch_uart_interrupt(int irq, void *dev_id)
                                 ret = handle_tx(priv);
                         break;
                 case PCH_UART_IID_MS:   /* Modem Status */
-                        ret = PCH_UART_HANDLED_MS_INT;
+                        msr = pch_uart_hal_get_modem(priv);
+                        next = 0; /* MS ir prioirty is the lowest. So, MS ir
+                                     means final interrupt */
+                        if ((msr & UART_MSR_ANY_DELTA) == 0)
+                                break;
+                        ret |= PCH_UART_HANDLED_MS_INT;
                         break;
                 default:        /* Never junp to this label */
                         dev_err(priv->port.dev, "%s:iid=%02x (%lu)\n", __func__,
                                 iid, jiffies);
                         ret = -1;
+                        next = 0;
                         break;
                 }
                 handled |= (unsigned int)ret;