[PATCH 5.7 151/179] serial: tegra: fix CREAD handling for PIO

From: Greg Kroah-Hartman
Date: Mon Jul 27 2020 - 10:26:27 EST

From: Johan Hovold <johan@xxxxxxxxxx>

commit b374c562ee7ab3f3a1daf959c01868bae761571c upstream.

Commit 33ae787b74fc ("serial: tegra: add support to ignore read") added
support for dropping input in case CREAD isn't set, but for PIO the
ignore_status_mask wasn't checked until after the character had been
put in the receive buffer.

Note that the NULL tty-port test is bogus and will be removed by a
follow-on patch.

Fixes: 33ae787b74fc ("serial: tegra: add support to ignore read")
Cc: stable <stable@xxxxxxxxxxxxxxx> # 5.4
Cc: Shardar Shariff Md <smohammed@xxxxxxxxxx>
Cc: Krishna Yarlagadda <kyarlagadda@xxxxxxxxxx>
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Acked-by: Thierry Reding <treding@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200710135947.2737-2-johan@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/tty/serial/serial-tegra.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/tty/serial/serial-tegra.c
+++ b/drivers/tty/serial/serial-tegra.c
@@ -653,11 +653,14 @@ static void tegra_uart_handle_rx_pio(str
ch = (unsigned char) tegra_uart_read(tup, UART_RX);

- if (!uart_handle_sysrq_char(&tup->uport, ch) && tty)
- tty_insert_flip_char(tty, ch, flag);
+ if (uart_handle_sysrq_char(&tup->uport, ch))
+ continue;

if (tup->uport.ignore_status_mask & UART_LSR_DR)
+ if (tty)
+ tty_insert_flip_char(tty, ch, flag);
} while (1);