[SERIAL] Clean up handling of LSR in receive function.

It's pointless accessing the LSR value via a pointer all the time -
it prevents the compiler optimising it.  Also, ensure that we
recognise a break sent during a kernel printk correctly.

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 09b3be12c248bf331453589b07272f57112dd9af..7232f14f3d594466f2f240aa5cda4fbcf380682d 100644 (file)
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -958,7 +958,7 @@ static _INLINE_ void
 receive_chars(struct uart_8250_port *up, int *status, struct pt_regs *regs)
 {
        struct tty_struct *tty = up->port.info->tty;
-       unsigned char ch;
+       unsigned char ch, lsr = *status;
        int max_count = 256;
 
        do {
@@ -972,13 +972,23 @@ receive_chars(struct uart_8250_port *up, int *status, struct pt_regs *regs)
                *tty->flip.flag_buf_ptr = TTY_NORMAL;
                up->port.icount.rx++;
 
-               if (unlikely(*status & (UART_LSR_BI | UART_LSR_PE |
-                                      UART_LSR_FE | UART_LSR_OE))) {
+#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
+
+               if (unlikely(lsr & (UART_LSR_BI | UART_LSR_PE |
+                                   UART_LSR_FE | UART_LSR_OE))) {
                        /*
                         * For statistics only
                         */
-                       if (*status & UART_LSR_BI) {
-                               *status &= ~(UART_LSR_FE | UART_LSR_PE);
+                       if (lsr & UART_LSR_BI) {
+                               lsr &= ~(UART_LSR_FE | UART_LSR_PE);
                                up->port.icount.brk++;
                                /*
                                 * We do the SysRQ and SAK checking
@@ -988,41 +998,34 @@ receive_chars(struct uart_8250_port *up, int *status, struct pt_regs *regs)
                                 */
                                if (uart_handle_break(&up->port))
                                        goto ignore_char;
-                       } else if (*status & UART_LSR_PE)
+                       } else if (lsr & UART_LSR_PE)
                                up->port.icount.parity++;
-                       else if (*status & UART_LSR_FE)
+                       else if (lsr & UART_LSR_FE)
                                up->port.icount.frame++;
-                       if (*status & UART_LSR_OE)
+                       if (lsr & UART_LSR_OE)
                                up->port.icount.overrun++;
 
                        /*
                         * Mask off conditions which should be ingored.
                         */
-                       *status &= up->port.read_status_mask;
+                       lsr &= up->port.read_status_mask;
 
-#ifdef CONFIG_SERIAL_8250_CONSOLE
-                       if (up->port.line == up->port.cons->index) {
-                               /* Recover the break flag from console xmit */
-                               *status |= up->lsr_break_flag;
-                               up->lsr_break_flag = 0;
-                       }
-#endif
-                       if (*status & UART_LSR_BI) {
+                       if (lsr & UART_LSR_BI) {
                                DEBUG_INTR("handling break....");
                                *tty->flip.flag_buf_ptr = TTY_BREAK;
-                       } else if (*status & UART_LSR_PE)
+                       } else if (lsr & UART_LSR_PE)
                                *tty->flip.flag_buf_ptr = TTY_PARITY;
-                       else if (*status & UART_LSR_FE)
+                       else if (lsr & UART_LSR_FE)
                                *tty->flip.flag_buf_ptr = TTY_FRAME;
                }
                if (uart_handle_sysrq_char(&up->port, ch, regs))
                        goto ignore_char;
-               if ((*status & up->port.ignore_status_mask) == 0) {
+               if ((lsr & up->port.ignore_status_mask) == 0) {
                        tty->flip.flag_buf_ptr++;
                        tty->flip.char_buf_ptr++;
                        tty->flip.count++;
                }
-               if ((*status & UART_LSR_OE) &&
+               if ((lsr & UART_LSR_OE) &&
                    tty->flip.count < TTY_FLIPBUF_SIZE) {
                        /*
                         * Overrun is special, since it's reported
@@ -1035,9 +1038,10 @@ receive_chars(struct uart_8250_port *up, int *status, struct pt_regs *regs)
                        tty->flip.count++;
                }
        ignore_char:
-               *status = serial_inp(up, UART_LSR);
-       } while ((*status & UART_LSR_DR) && (max_count-- > 0));
+               lsr = serial_inp(up, UART_LSR);
+       } while ((lsr & UART_LSR_DR) && (max_count-- > 0));
        tty_flip_buffer_push(tty);
+       *status = lsr;
 }
 
 static _INLINE_ void transmit_chars(struct uart_8250_port *up)