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authorStephen Warren <swarren@nvidia.com>2011-05-17 16:12:37 -0600
committerGreg Kroah-Hartman <gregkh@suse.de>2011-05-19 16:51:02 -0700
commit5f873bae704cf8b7cbd64b5720912266286c9146 (patch)
tree0e861218bdb25d0ad3f41aa569f89d0f56d59d18 /drivers/tty
parent4539c24fe4f92c09ee668ef959d3e8180df619b9 (diff)
tty/serial: Fix break handling for PORT_TEGRA
When a break is received, Tegra's UART apparently fills the FIFO with 0 bytes. These must be drained so that they aren't interpreted as actual data received. This allows e.g. MAGIC_SYSRQ to work on Tegra's UARTs. v2: Added FIXME comment to clear_rx_fifo Originally-by: Laxman Dewangan <ldewangan@nvidia.com> Cc: Laxman Dewangan <ldewangan@nvidia.com> Signed-off-by: Stephen Warren <swarren@nvidia.com> Acked-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/tty')
-rw-r--r--drivers/tty/serial/8250.c28
1 files changed, 28 insertions, 0 deletions
diff --git a/drivers/tty/serial/8250.c b/drivers/tty/serial/8250.c
index a5e290de8c9..b40f7b90c81 100644
--- a/drivers/tty/serial/8250.c
+++ b/drivers/tty/serial/8250.c
@@ -1433,6 +1433,27 @@ static void serial8250_enable_ms(struct uart_port *port)
serial_out(up, UART_IER, up->ier);
}
+/*
+ * Clear the Tegra rx fifo after a break
+ *
+ * FIXME: This needs to become a port specific callback once we have a
+ * framework for this
+ */
+static void clear_rx_fifo(struct uart_8250_port *up)
+{
+ unsigned int status, tmout = 10000;
+ do {
+ status = serial_in(up, UART_LSR);
+ if (status & (UART_LSR_FIFOE | UART_LSR_BRK_ERROR_BITS))
+ status = serial_in(up, UART_RX);
+ else
+ break;
+ if (--tmout == 0)
+ break;
+ udelay(1);
+ } while (1);
+}
+
static void
receive_chars(struct uart_8250_port *up, unsigned int *status)
{
@@ -1468,6 +1489,13 @@ receive_chars(struct uart_8250_port *up, unsigned int *status)
lsr &= ~(UART_LSR_FE | UART_LSR_PE);
up->port.icount.brk++;
/*
+ * If tegra port then clear the rx fifo to
+ * accept another break/character.
+ */
+ if (up->port.type == PORT_TEGRA)
+ clear_rx_fifo(up);
+
+ /*
* We do the SysRQ and SAK checking
* here because otherwise the break
* may get masked by ignore_status_mask