1 files changed, 134 insertions, 44 deletions

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 2964ca9df5a0..98ec86185328 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -364,6 +364,23 @@ serial_out(struct uart_8250_port *up, int offset, int value)
         }
 }
 
+static void
+serial_out_sync(struct uart_8250_port *up, int offset, int value)
+{
+        switch (up->port.iotype) {
+        case UPIO_MEM:
+        case UPIO_MEM32:
+#ifdef CONFIG_SERIAL_8250_AU1X00
+        case UPIO_AU:
+#endif
+                serial_out(up, offset, value);
+                serial_in(up, UART_LCR);        /* safe, no side-effects */
+                break;
+        default:
+                serial_out(up, offset, value);
+        }
+}
+
 /*
  * We used to support using pause I/O for certain machines.  We
  * haven't supported this for a while, but just in case it's badly
@@ -1045,7 +1062,7 @@ static void autoconfig(struct uart_8250_port *up, unsigned int probeflags)
 #endif
         serial_outp(up, UART_MCR, save_mcr);
         serial8250_clear_fifos(up);
-        (void)serial_in(up, UART_RX);
+        serial_in(up, UART_RX);
         if (up->capabilities & UART_CAP_UUE)
                 serial_outp(up, UART_IER, UART_IER_UUE);
         else
@@ -1451,6 +1468,12 @@ static void serial_unlink_irq_chain(struct uart_8250_port *up)
         serial_do_unlink(i, up);
 }
 
+/* Base timer interval for polling */
+static inline int poll_timeout(int timeout)
+{
+        return timeout > 6 ? (timeout / 2 - 2) : 1;
+}
+
 /*
  * This function is used to handle ports that do not have an
  * interrupt.  This doesn't work very well for 16450's, but gives
@@ -1460,16 +1483,51 @@ static void serial_unlink_irq_chain(struct uart_8250_port *up)
 static void serial8250_timeout(unsigned long data)
 {
         struct uart_8250_port *up = (struct uart_8250_port *)data;
-        unsigned int timeout;
         unsigned int iir;
 
         iir = serial_in(up, UART_IIR);
         if (!(iir & UART_IIR_NO_INT))
                 serial8250_handle_port(up);
+        mod_timer(&up->timer, jiffies + poll_timeout(up->port.timeout));
+}
+
+static void serial8250_backup_timeout(unsigned long data)
+{
+        struct uart_8250_port *up = (struct uart_8250_port *)data;
+        unsigned int iir, ier = 0;
+
+        /*
+         * Must disable interrupts or else we risk racing with the interrupt
+         * based handler.
+         */
+        if (is_real_interrupt(up->port.irq)) {
+                ier = serial_in(up, UART_IER);
+                serial_out(up, UART_IER, 0);
+        }
 
-        timeout = up->port.timeout;
-        timeout = timeout > 6 ? (timeout / 2 - 2) : 1;
-        mod_timer(&up->timer, jiffies + timeout);
+        iir = serial_in(up, UART_IIR);
+
+        /*
+         * This should be a safe test for anyone who doesn't trust the
+         * IIR bits on their UART, but it's specifically designed for
+         * the "Diva" UART used on the management processor on many HP
+         * ia64 and parisc boxes.
+         */
+        if ((iir & UART_IIR_NO_INT) && (up->ier & UART_IER_THRI) &&
+            (!uart_circ_empty(&up->port.info->xmit) || up->port.x_char) &&
+            (serial_in(up, UART_LSR) & UART_LSR_THRE)) {
+                iir &= ~(UART_IIR_ID | UART_IIR_NO_INT);
+                iir |= UART_IIR_THRI;
+        }
+
+        if (!(iir & UART_IIR_NO_INT))
+                serial8250_handle_port(up);
+
+        if (is_real_interrupt(up->port.irq))
+                serial_out(up, UART_IER, ier);
+
+        /* Standard timer interval plus 0.2s to keep the port running */
+        mod_timer(&up->timer, jiffies + poll_timeout(up->port.timeout) + HZ/5);
 }
 
 static unsigned int serial8250_tx_empty(struct uart_port *port)
@@ -1540,6 +1598,37 @@ static void serial8250_break_ctl(struct uart_port *port, int break_state)
         spin_unlock_irqrestore(&up->port.lock, flags);
 }
 
+#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
+
+/*
+ *      Wait for transmitter & holding register to empty
+ */
+static inline void wait_for_xmitr(struct uart_8250_port *up, int bits)
+{
+        unsigned int status, tmout = 10000;
+
+        /* Wait up to 10ms for the character(s) to be sent. */
+        do {
+                status = serial_in(up, UART_LSR);
+
+                if (status & UART_LSR_BI)
+                        up->lsr_break_flag = UART_LSR_BI;
+
+                if (--tmout == 0)
+                        break;
+                udelay(1);
+        } while ((status & bits) != bits);
+
+        /* Wait up to 1s for flow control if necessary */
+        if (up->port.flags & UPF_CONS_FLOW) {
+                tmout = 1000000;
+                while (!(serial_in(up, UART_MSR) & UART_MSR_CTS) && --tmout) {
+                        udelay(1);
+                        touch_nmi_watchdog();
+                }
+        }
+}
+
 static int serial8250_startup(struct uart_port *port)
 {
         struct uart_8250_port *up = (struct uart_8250_port *)port;
@@ -1613,18 +1702,50 @@ static int serial8250_startup(struct uart_port *port)
                 serial_outp(up, UART_LCR, 0);
         }
 
+        if (is_real_interrupt(up->port.irq)) {
+                /*
+                 * Test for UARTs that do not reassert THRE when the
+                 * transmitter is idle and the interrupt has already
+                 * been cleared.  Real 16550s should always reassert
+                 * this interrupt whenever the transmitter is idle and
+                 * the interrupt is enabled.  Delays are necessary to
+                 * allow register changes to become visible.
+                 */
+                spin_lock_irqsave(&up->port.lock, flags);
+
+                wait_for_xmitr(up, UART_LSR_THRE);
+                serial_out_sync(up, UART_IER, UART_IER_THRI);
+                udelay(1); /* allow THRE to set */
+                serial_in(up, UART_IIR);
+                serial_out(up, UART_IER, 0);
+                serial_out_sync(up, UART_IER, UART_IER_THRI);
+                udelay(1); /* allow a working UART time to re-assert THRE */
+                iir = serial_in(up, UART_IIR);
+                serial_out(up, UART_IER, 0);
+
+                spin_unlock_irqrestore(&up->port.lock, flags);
+
+                /*
+                 * If the interrupt is not reasserted, setup a timer to
+                 * kick the UART on a regular basis.
+                 */
+                if (iir & UART_IIR_NO_INT) {
+                        pr_debug("ttyS%d - using backup timer\n", port->line);
+                        up->timer.function = serial8250_backup_timeout;
+                        up->timer.data = (unsigned long)up;
+                        mod_timer(&up->timer, jiffies +
+                                  poll_timeout(up->port.timeout) + HZ/5);
+                }
+        }
+
         /*
          * If the "interrupt" for this port doesn't correspond with any
          * hardware interrupt, we use a timer-based system.  The original
          * driver used to do this with IRQ0.
          */
         if (!is_real_interrupt(up->port.irq)) {
-                unsigned int timeout = up->port.timeout;
-
-                timeout = timeout > 6 ? (timeout / 2 - 2) : 1;
-
                 up->timer.data = (unsigned long)up;
-                mod_timer(&up->timer, jiffies + timeout);
+                mod_timer(&up->timer, jiffies + poll_timeout(up->port.timeout));
         } else {
                 retval = serial_link_irq_chain(up);
                 if (retval)
@@ -1740,9 +1861,9 @@ static void serial8250_shutdown(struct uart_port *port)
          */
         (void) serial_in(up, UART_RX);
 
-        if (!is_real_interrupt(up->port.irq))
-                del_timer_sync(&up->timer);
-        else
+        del_timer_sync(&up->timer);
+        up->timer.function = serial8250_timeout;
+        if (is_real_interrupt(up->port.irq))
                 serial_unlink_irq_chain(up);
 }
 
@@ -2212,37 +2333,6 @@ serial8250_register_ports(struct uart_driver *drv, struct device *dev)
 
 #ifdef CONFIG_SERIAL_8250_CONSOLE
 
-#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
-
-/*
- *      Wait for transmitter & holding register to empty
- */
-static inline void wait_for_xmitr(struct uart_8250_port *up, int bits)
-{
-        unsigned int status, tmout = 10000;
-
-        /* Wait up to 10ms for the character(s) to be sent. */
-        do {
-                status = serial_in(up, UART_LSR);
-
-                if (status & UART_LSR_BI)
-                        up->lsr_break_flag = UART_LSR_BI;
-
-                if (--tmout == 0)
-                        break;
-                udelay(1);
-        } while ((status & bits) != bits);
-
-        /* Wait up to 1s for flow control if necessary */
-        if (up->port.flags & UPF_CONS_FLOW) {
-                tmout = 1000000;
-                while (!(serial_in(up, UART_MSR) & UART_MSR_CTS) && --tmout) {
-                        udelay(1);
-                        touch_nmi_watchdog();
-                }
-        }
-}
-
 static void serial8250_console_putchar(struct uart_port *port, int ch)
 {
         struct uart_8250_port *up = (struct uart_8250_port *)port;