serial: Test for no tx data on tx restart

Commit 717f3bbab3c7628736ef738fdbf3d9a28578c26c,
'serial_core: Fix conditional start_tx on ring buffer not empty'
exposes an incorrect assumption in several drivers' start_tx methods;
the tx ring buffer can, in fact, be empty when restarting tx while
performing flow control.

Affected drivers:
sunsab.c
ip22zilog.c
pmac_zilog.c
sunzilog.c
m32r_sio.c
imx.c

Other in-tree serial drivers either are not affected or already
test for empty tx ring buffer before transmitting.

Test for empty tx ring buffer in start_tx() method, after transmitting
x_char (if applicable).

Reported-by: Aaro Koskinen <[email protected]>
Cc: Seth Bollinger <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Sam Ravnborg <[email protected]>
Cc: Thomas Bogendoerfer <[email protected]>
Signed-off-by: Peter Hurley <[email protected]>
Cc: stable <[email protected]> # 3.15
Signed-off-by: Greg Kroah-Hartman <[email protected]>

0 files changed, 0 insertions, 0 deletions