2 files changed, 57 insertions, 29 deletions

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 301313002f6b..f94109cbb46e 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -129,7 +129,16 @@ struct uart_8250_port {
         unsigned char           mcr;
         unsigned char           mcr_mask;       /* mask of user bits */
         unsigned char           mcr_force;      /* mask of forced bits */
-        unsigned char           lsr_break_flag;
+
+        /*
+         * Some bits in registers are cleared on a read, so they must
+         * be saved whenever the register is read but the bits will not
+         * be immediately processed.
+         */
+#define LSR_SAVE_FLAGS UART_LSR_BRK_ERROR_BITS
+        unsigned char           lsr_saved_flags;
+#define MSR_SAVE_FLAGS UART_MSR_ANY_DELTA
+        unsigned char           msr_saved_flags;
 
         /*
          * We provide a per-port pm hook.
@@ -1238,6 +1247,7 @@ static void serial8250_start_tx(struct uart_port *port)
                 if (up->bugs & UART_BUG_TXEN) {
                         unsigned char lsr, iir;
                         lsr = serial_in(up, UART_LSR);
+                        up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
                         iir = serial_in(up, UART_IIR) & 0x0f;
                         if ((up->port.type == PORT_RM9000) ?
                                 (lsr & UART_LSR_THRE &&
@@ -1290,18 +1300,10 @@ receive_chars(struct uart_8250_port *up, unsigned int *status)
                 flag = TTY_NORMAL;
                 up->port.icount.rx++;
 
-#ifdef CONFIG_SERIAL_8250_CONSOLE
-                /*
-                 * Recover the break flag from console xmit
-                 */
-                if (up->port.line == up->port.cons->index) {
-                        lsr |= up->lsr_break_flag;
-                        up->lsr_break_flag = 0;
-                }
-#endif
+                lsr |= up->lsr_saved_flags;
+                up->lsr_saved_flags = 0;
 
-                if (unlikely(lsr & (UART_LSR_BI | UART_LSR_PE |
-                                    UART_LSR_FE | UART_LSR_OE))) {
+                if (unlikely(lsr & UART_LSR_BRK_ERROR_BITS)) {
                         /*
                          * For statistics only
                          */
@@ -1392,6 +1394,8 @@ static unsigned int check_modem_status(struct uart_8250_port *up)
 {
         unsigned int status = serial_in(up, UART_MSR);
 
+        status |= up->msr_saved_flags;
+        up->msr_saved_flags = 0;
         if (status & UART_MSR_ANY_DELTA && up->ier & UART_IER_MSI &&
             up->port.info != NULL) {
                 if (status & UART_MSR_TERI)
@@ -1591,7 +1595,8 @@ static void serial8250_timeout(unsigned long data)
 static void serial8250_backup_timeout(unsigned long data)
 {
         struct uart_8250_port *up = (struct uart_8250_port *)data;
-        unsigned int iir, ier = 0;
+        unsigned int iir, ier = 0, lsr;
+        unsigned long flags;
 
         /*
          * Must disable interrupts or else we risk racing with the interrupt
@@ -1610,9 +1615,13 @@ static void serial8250_backup_timeout(unsigned long data)
          * the "Diva" UART used on the management processor on many HP
          * ia64 and parisc boxes.
          */
+        spin_lock_irqsave(&up->port.lock, flags);
+        lsr = serial_in(up, UART_LSR);
+        up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
+        spin_unlock_irqrestore(&up->port.lock, flags);
         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)) {
+            (lsr & UART_LSR_THRE)) {
                 iir &= ~(UART_IIR_ID | UART_IIR_NO_INT);
                 iir |= UART_IIR_THRI;
         }
@@ -1631,13 +1640,14 @@ static unsigned int serial8250_tx_empty(struct uart_port *port)
 {
         struct uart_8250_port *up = (struct uart_8250_port *)port;
         unsigned long flags;
-        unsigned int ret;
+        unsigned int lsr;
 
         spin_lock_irqsave(&up->port.lock, flags);
-        ret = serial_in(up, UART_LSR) & UART_LSR_TEMT ? TIOCSER_TEMT : 0;
+        lsr = serial_in(up, UART_LSR);
+        up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
         spin_unlock_irqrestore(&up->port.lock, flags);
 
-        return ret;
+        return lsr & UART_LSR_TEMT ? TIOCSER_TEMT : 0;
 }
 
 static unsigned int serial8250_get_mctrl(struct uart_port *port)
@@ -1708,8 +1718,7 @@ static inline void wait_for_xmitr(struct uart_8250_port *up, int bits)
         do {
                 status = serial_in(up, UART_LSR);
 
-                if (status & UART_LSR_BI)
-                        up->lsr_break_flag = UART_LSR_BI;
+                up->lsr_saved_flags |= status & LSR_SAVE_FLAGS;
 
                 if (--tmout == 0)
                         break;
@@ -1718,8 +1727,12 @@ static inline void wait_for_xmitr(struct uart_8250_port *up, int 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) {
+                unsigned int tmout;
+                for (tmout = 1000000; tmout; tmout--) {
+                        unsigned int msr = serial_in(up, UART_MSR);
+                        up->msr_saved_flags |= msr & MSR_SAVE_FLAGS;
+                        if (msr & UART_MSR_CTS)
+                                break;
                         udelay(1);
                         touch_nmi_watchdog();
                 }
@@ -1889,6 +1902,18 @@ static int serial8250_startup(struct uart_port *port)
         spin_unlock_irqrestore(&up->port.lock, flags);
 
         /*
+         * Clear the interrupt registers again for luck, and clear the
+         * saved flags to avoid getting false values from polling
+         * routines or the previous session.
+         */
+        serial_inp(up, UART_LSR);
+        serial_inp(up, UART_RX);
+        serial_inp(up, UART_IIR);
+        serial_inp(up, UART_MSR);
+        up->lsr_saved_flags = 0;
+        up->msr_saved_flags = 0;
+
+        /*
          * Finally, enable interrupts.  Note: Modem status interrupts
          * are set via set_termios(), which will be occurring imminently
          * anyway, so we don't enable them here.
@@ -1906,14 +1931,6 @@ static int serial8250_startup(struct uart_port *port)
                 (void) inb_p(icp);
         }
 
-        /*
-         * And clear the interrupt registers again for luck.
-         */
-        (void) serial_inp(up, UART_LSR);
-        (void) serial_inp(up, UART_RX);
-        (void) serial_inp(up, UART_IIR);
-        (void) serial_inp(up, UART_MSR);
-
         return 0;
 }
 
@@ -2484,6 +2501,16 @@ serial8250_console_write(struct console *co, const char *s, unsigned int count)
         wait_for_xmitr(up, BOTH_EMPTY);
         serial_out(up, UART_IER, ier);
 
+        /*
+         *      The receive handling will happen properly because the
+         *      receive ready bit will still be set; it is not cleared
+         *      on read.  However, modem control will not, we must
+         *      call it if we have saved something in the saved flags
+         *      while processing with interrupts off.
+         */
+        if (up->msr_saved_flags)
+                check_modem_status(up);
+
         if (locked)
                 spin_unlock(&up->port.lock);
         local_irq_restore(flags);
diff --git a/include/linux/serial_reg.h b/include/linux/serial_reg.h
index 1c5ed7d92b0f..96c0d93fc2ca 100644
--- a/include/linux/serial_reg.h
+++ b/include/linux/serial_reg.h
@@ -118,6 +118,7 @@
 #define UART_LSR_PE             0x04 /* Parity error indicator */
 #define UART_LSR_OE             0x02 /* Overrun error indicator */
 #define UART_LSR_DR             0x01 /* Receiver data ready */
+#define UART_LSR_BRK_ERROR_BITS 0x1E /* BI, FE, PE, OE bits */
 
 #define UART_MSR        6       /* In:  Modem Status Register */
 #define UART_MSR_DCD            0x80 /* Data Carrier Detect */