[PATCH 4.4 69/86] serial: 8250_mid: recognize interrupt source in handler

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>

commit c42850f1ae7e70056f852e67bb9dddf927853b47 upstream.

There is a special register that shows interrupt status by source. In
particular case the source can be a combination of DMA Tx, DMA Rx, and UART.

Read the register and call the handlers only for sources that request an
interrupt.

Fixes: 6ede6dcd87aa ("serial: 8250_mid: add support for DMA engine handling from UART MMIO")
Reviewed-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/tty/serial/8250/8250_mid.c |   19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

--- a/drivers/tty/serial/8250/8250_mid.c
+++ b/drivers/tty/serial/8250/8250_mid.c
@@ -25,6 +25,7 @@
 #define PCI_DEVICE_ID_INTEL_DNV_UART	0x19d8
 
 /* Intel MID Specific registers */
+#define INTEL_MID_UART_DNV_FISR		0x08
 #define INTEL_MID_UART_PS		0x30
 #define INTEL_MID_UART_MUL		0x34
 #define INTEL_MID_UART_DIV		0x38
@@ -90,16 +91,16 @@ static int tng_setup(struct mid8250 *mid
 static int dnv_handle_irq(struct uart_port *p)
 {
 	struct mid8250 *mid = p->private_data;
-	int ret;
+	unsigned int fisr = serial_port_in(p, INTEL_MID_UART_DNV_FISR);
+	int ret = IRQ_NONE;
 
-	ret = hsu_dma_irq(&mid->dma_chip, 0);
-	ret |= hsu_dma_irq(&mid->dma_chip, 1);
-
-	/* For now, letting the HW generate separate interrupt for the UART */
-	if (ret)
-		return ret;
-
-	return serial8250_handle_irq(p, serial_port_in(p, UART_IIR));
+	if (fisr & BIT(2))
+		ret |= hsu_dma_irq(&mid->dma_chip, 1);
+	if (fisr & BIT(1))
+		ret |= hsu_dma_irq(&mid->dma_chip, 0);
+	if (fisr & BIT(0))
+		ret |= serial8250_handle_irq(p, serial_port_in(p, UART_IIR));
+	return ret;
 }
 
 #define DNV_DMA_CHAN_OFFSET 0x80