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Subject[PATCH] 8250: fix break handling for Intel 82571
Intel 82571 has a "Serial Over LAN" feature that doesn't properly implements
the receiving of break characters. When a break is received, it doesn't set
UART_LSR_DR and unless another character is received, the break won't be
received by the application.

Signed-off-by: Aristeu Rozanski <arozansk@redhat.com>

---
drivers/serial/8250.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)
--- linus-2.6.orig/drivers/serial/8250.c 2008-05-15 13:32:48.000000000 -0400
+++ linus-2.6/drivers/serial/8250.c 2008-05-15 13:48:59.000000000 -0400
@@ -1296,7 +1296,18 @@ receive_chars(struct uart_8250_port *up,
char flag;

do {
- ch = serial_inp(up, UART_RX);
+ if (likely(lsr & UART_LSR_DR))
+ ch = serial_inp(up, UART_RX);
+ else
+ /*
+ * Intel 82571 has a Serial Over Lan device that will
+ * set UART_LSR_BI without setting UART_LSR_DR when
+ * it receives a break. To avoid reading from the
+ * receive buffer without UART_LSR_DR bit set, we
+ * just force the read character to be 0
+ */
+ ch = 0;
+
flag = TTY_NORMAL;
up->port.icount.rx++;

@@ -1345,7 +1356,7 @@ receive_chars(struct uart_8250_port *up,

ignore_char:
lsr = serial_inp(up, UART_LSR);
- } while ((lsr & UART_LSR_DR) && (max_count-- > 0));
+ } while ((lsr & (UART_LSR_DR | UART_LSR_BI)) && (max_count-- > 0));
spin_unlock(&up->port.lock);
tty_flip_buffer_push(tty);
spin_lock(&up->port.lock);
@@ -1428,7 +1439,7 @@ serial8250_handle_port(struct uart_8250_

DEBUG_INTR("status = %x...", status);

- if (status & UART_LSR_DR)
+ if (status & (UART_LSR_DR | UART_LSR_BI))
receive_chars(up, &status);
check_modem_status(up);
if (status & UART_LSR_THRE)


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