serial: do not treat the IIR register as a bitfield

It seems that at some point, someone made the assumption that the UART
Interrupt ID Register was a bitfield and started to check if certain
bits where set.

Actually however the register contains interrupt ID's where only the MSB
seems to be used singular and the rest share at least one bit. Thus
doing bitfield operations is wrong.

This patch cleans up the serial_reg include file by ordering it and
replacing the UART_IIR_ID 'mask' with a proper mask for the register.
The OMAP uart appears to have used the two commonly 'reserved' bits 4
and 5 and thus get an UART_IIR_EXT_MASK for these two bits.

This patch then goes over all UART_IIR_* users and changes the code from
bitfield checking, to ID checking instead.

Signed-off-by: Olliver Schinagl <[email protected]>

drivers/tty/serial/8250/8250_core.c

@@ -288,6 +288,7 @@ static void serial8250_backup_timeout(unsigned long data)
 	}
 
 	iir = serial_in(up, UART_IIR);
+	iir &= UART_IIR_MASK;
 
 	/*
 	 * This should be a safe test for anyone who doesn't trust the
@@ -297,14 +298,15 @@ static void serial8250_backup_timeout(unsigned long data)
 	 */
 	lsr = serial_in(up, UART_LSR);
 	up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
-	if ((iir & UART_IIR_NO_INT) && (up->ier & UART_IER_THRI) &&
+	if ((iir == UART_IIR_NO_INT) &&
+	    (up->ier & UART_IER_THRI) &&
 	    (!uart_circ_empty(&up->port.state->xmit) || up->port.x_char) &&
 	    (lsr & UART_LSR_THRE)) {
-		iir &= ~(UART_IIR_ID | UART_IIR_NO_INT);
+		iir &= ~(UART_IIR_MASK);
 		iir |= UART_IIR_THRI;
 	}
 
-	if (!(iir & UART_IIR_NO_INT))
+	if (iir != UART_IIR_NO_INT)
 		serial8250_tx_chars(up);
 
 	if (up->port.irq)

drivers/tty/serial/8250/8250_dw.c

@@ -217,7 +217,8 @@ static int dw8250_handle_irq(struct uart_port *p)
 	 * This problem has only been observed so far when not in DMA mode
 	 * so we limit the workaround only to non-DMA mode.
 	 */
-	if (!up->dma && ((iir & 0x3f) == UART_IIR_RX_TIMEOUT)) {
+	iir &= UART_IIR_MASK;
+	if (!up->dma && (iir == UART_IIR_RX_TIMEOUT)) {
 		spin_lock_irqsave(&p->lock, flags);
 		status = p->serial_in(p, UART_LSR);
 
@@ -230,7 +231,7 @@ static int dw8250_handle_irq(struct uart_port *p)
 	if (serial8250_handle_irq(p, iir))
 		return 1;
 
-	if ((iir & UART_IIR_BUSY) == UART_IIR_BUSY) {
+	if (iir == UART_IIR_BUSY) {
 		/* Clear the USR */
 		(void)p->serial_in(p, d->usr_reg);
 

drivers/tty/serial/8250/8250_fsl.c

@@ -33,7 +33,8 @@ int fsl8250_handle_irq(struct uart_port *port)
 	spin_lock_irqsave(&up->port.lock, flags);
 
 	iir = port->serial_in(port, UART_IIR);
-	if (iir & UART_IIR_NO_INT) {
+	iir &= UART_IIR_MASK;
+	if (iir == UART_IIR_NO_INT) {
 		spin_unlock_irqrestore(&up->port.lock, flags);
 		return 0;
 	}

drivers/tty/serial/8250/8250_omap.c

@@ -1019,7 +1019,7 @@ static int omap_8250_tx_dma(struct uart_8250_port *p)
 
 static bool handle_rx_dma(struct uart_8250_port *up, unsigned int iir)
 {
-	switch (iir & 0x3f) {
+	switch (iir & (UART_IIR_MASK | UART_IIR_EXT_MASK)) {
 	case UART_IIR_RLSI:
 	case UART_IIR_RX_TIMEOUT:
 	case UART_IIR_RDI:
@@ -1044,7 +1044,7 @@ static int omap_8250_dma_handle_irq(struct uart_port *port)
 	serial8250_rpm_get(up);
 
 	iir = serial_port_in(port, UART_IIR);
-	if (iir & UART_IIR_NO_INT) {
+	if ((iir & UART_IIR_MASK) == UART_IIR_NO_INT) {
 		serial8250_rpm_put(up);
 		return 0;
 	}

drivers/tty/serial/8250/8250_port.c

@@ -1836,7 +1836,7 @@ EXPORT_SYMBOL_GPL(serial8250_modem_status);
 
 static bool handle_rx_dma(struct uart_8250_port *up, unsigned int iir)
 {
-	switch (iir & 0x3f) {
+	switch (iir & UART_IIR_MASK) {
 	case UART_IIR_RX_TIMEOUT:
 		serial8250_rx_dma_flush(up);
 		/* fall-through */
@@ -1855,7 +1855,7 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
 	unsigned long flags;
 	struct uart_8250_port *up = up_to_u8250p(port);
 
-	if (iir & UART_IIR_NO_INT)
+	if ((iir & UART_IIR_MASK) == UART_IIR_NO_INT)
 		return 0;
 
 	spin_lock_irqsave(&port->lock, flags);
@@ -1922,7 +1922,7 @@ static int serial8250_tx_threshold_handle_irq(struct uart_port *port)
 	unsigned int iir = serial_port_in(port, UART_IIR);
 
 	/* TX Threshold IRQ triggered so load up FIFO */
-	if ((iir & UART_IIR_ID) == UART_IIR_THRI) {
+	if ((iir & UART_IIR_MASK) == UART_IIR_THRI) {
 		struct uart_8250_port *up = up_to_u8250p(port);
 
 		spin_lock_irqsave(&port->lock, flags);
@@ -2290,7 +2290,8 @@ int serial8250_do_startup(struct uart_port *port)
 		 * don't trust the iir, setup a timer to kick the UART
 		 * on a regular basis.
 		 */
-		if ((!(iir1 & UART_IIR_NO_INT) && (iir & UART_IIR_NO_INT)) ||
+		if ((((iir1 & UART_IIR_MASK) != UART_IIR_NO_INT) &&
+		     ((iir & UART_IIR_MASK) == UART_IIR_NO_INT)) ||
 		    up->port.flags & UPF_BUG_THRE) {
 			up->bugs |= UART_BUG_THRE;
 		}
@@ -2341,7 +2342,7 @@ int serial8250_do_startup(struct uart_port *port)
 	iir = serial_port_in(port, UART_IIR);
 	serial_port_out(port, UART_IER, 0);
 
-	if (lsr & UART_LSR_TEMT && iir & UART_IIR_NO_INT) {
+	if (lsr & UART_LSR_TEMT && ((iir & UART_IIR_MASK) == UART_IIR_NO_INT)) {
 		if (!(up->bugs & UART_BUG_TXEN)) {
 			up->bugs |= UART_BUG_TXEN;
 			pr_debug("ttyS%d - enabling bad tx status workarounds\n",

drivers/tty/serial/omap-serial.c

@@ -569,7 +569,6 @@ static irqreturn_t serial_omap_irq(int irq, void *dev_id)
 {
 	struct uart_omap_port *up = dev_id;
 	unsigned int iir, lsr;
-	unsigned int type;
 	irqreturn_t ret = IRQ_NONE;
 	int max_count = 256;
 
@@ -578,16 +577,15 @@ static irqreturn_t serial_omap_irq(int irq, void *dev_id)
 
 	do {
 		iir = serial_in(up, UART_IIR);
-		if (iir & UART_IIR_NO_INT)
+		iir &= (UART_IIR_MASK | UART_IIR_EXT_MASK);
+		if (iir == UART_IIR_NO_INT)
 			break;
 
 		ret = IRQ_HANDLED;
 		lsr = serial_in(up, UART_LSR);
 
 		/* extract IRQ type from IIR register */
-		type = iir & 0x3e;
-
-		switch (type) {
+		switch (iir) {
 		case UART_IIR_MSI:
 			check_modem_status(up);
 			break;
@@ -607,10 +605,12 @@ static irqreturn_t serial_omap_irq(int irq, void *dev_id)
 			break;
 		case UART_IIR_XOFF:
 			/* FALLTHROUGH */
+		case UART_IIR_BUSY:
+			/* FALLTHROUGH */
 		default:
 			break;
 		}
-	} while (!(iir & UART_IIR_NO_INT) && max_count--);
+	} while ((iir != UART_IIR_NO_INT) && max_count--);
 
 	spin_unlock(&up->port.lock);
 

drivers/tty/serial/pxa.c

@@ -253,7 +253,7 @@ static inline irqreturn_t serial_pxa_irq(int irq, void *dev_id)
 	unsigned int iir, lsr;
 
 	iir = serial_in(up, UART_IIR);
-	if (iir & UART_IIR_NO_INT)
+	if ((iir & UART_IIR_MASK) == UART_IIR_NO_INT)
 		return IRQ_NONE;
 	spin_lock(&up->port.lock);
 	lsr = serial_in(up, UART_LSR);

drivers/tty/serial/serial-tegra.c

@@ -691,7 +691,8 @@ static irqreturn_t tegra_uart_isr(int irq, void *data)
 	spin_lock_irqsave(&u->lock, flags);
 	while (1) {
 		iir = tegra_uart_read(tup, UART_IIR);
-		if (iir & UART_IIR_NO_INT) {
+		iir &= UART_IIR_MASK;
+		if (iir == UART_IIR_NO_INT) {
 			if (is_rx_int) {
 				tegra_uart_handle_rx_dma(tup);
 				if (tup->rx_in_progress) {

drivers/tty/serial/sunsu.c

@@ -475,7 +475,7 @@ static irqreturn_t sunsu_serial_interrupt(int irq, void *dev_id)
 
 		spin_lock_irqsave(&up->port.lock, flags);
 
-	} while (!(serial_in(up, UART_IIR) & UART_IIR_NO_INT));
+	} while ((serial_in(up, UART_IIR) & UART_IIR_MASK) != UART_IIR_NO_INT);
 
 	spin_unlock_irqrestore(&up->port.lock, flags);
 

drivers/tty/serial/vr41xx_siu.c

@@ -429,7 +429,7 @@ static irqreturn_t siu_interrupt(int irq, void *dev_id)
 	port = (struct uart_port *)dev_id;
 
 	iir = siu_read(port, UART_IIR);
-	if (iir & UART_IIR_NO_INT)
+	if ((iir & UART_IIR_MASK) == UART_IIR_NO_INT)
 		return IRQ_NONE;
 
 	lsr = siu_read(port, UART_LSR);

include/uapi/linux/serial_reg.h

@@ -31,18 +31,18 @@
 #define UART_IERX_SLEEP		0x10 /* Enable sleep mode */
 
 #define UART_IIR	2	/* In:  Interrupt ID Register */
-#define UART_IIR_NO_INT		0x01 /* No interrupts pending */
-#define UART_IIR_ID		0x0e /* Mask for the interrupt ID */
 #define UART_IIR_MSI		0x00 /* Modem status interrupt */
+#define UART_IIR_NO_INT		0x01 /* No interrupts pending */
 #define UART_IIR_THRI		0x02 /* Transmitter holding register empty */
 #define UART_IIR_RDI		0x04 /* Receiver data interrupt */
 #define UART_IIR_RLSI		0x06 /* Receiver line status interrupt */
-
 #define UART_IIR_BUSY		0x07 /* DesignWare APB Busy Detect */
+#define UART_IIR_RX_TIMEOUT	0x0c /* DesignWare RX Timeout interrupt */
+#define UART_IIR_MASK		0x0f /* DesignWare IIR mask */
 
-#define UART_IIR_RX_TIMEOUT	0x0c /* OMAP RX Timeout interrupt */
 #define UART_IIR_XOFF		0x10 /* OMAP XOFF/Special Character */
 #define UART_IIR_CTS_RTS_DSR	0x20 /* OMAP CTS/RTS/DSR Change */
+#define UART_IIR_EXT_MASK	0x30 /* OMAP extended IIR mask */
 
 #define UART_FCR	2	/* Out: FIFO Control Register */
 #define UART_FCR_ENABLE_FIFO	0x01 /* Enable the FIFO */