diff options
| author | Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com> | 2018-08-09 21:04:19 +0200 |
|---|---|---|
| committer | Simon Glass <sjg@chromium.org> | 2018-11-14 09:16:28 -0800 |
| commit | 6f57c34473d37b8da5e6a3764d0d377d748aeef1 (patch) | |
| tree | d6ab8dab8076d0dc5e7f7ad64b7d8dfb9be7a025 /drivers/serial | |
| parent | 81f351d6e7ebb371de8ea849fc21dd07dc2eff24 (diff) | |
serial: ns16550: fix debug uart putc called before init
If _debug_uart_putc() is called before _debug_uart_init(), the
ns16550 debug uart driver hangs in a tight loop waiting for the
tx FIFO to get empty.
As this can happen via a printf sneaking in before the port calls
debug_uart_init(), let's rather ignore characters before the debug
uart is initialized.
This is done by reading the baudrate divisor and aborting if is zero.
Tested on socfpga_cyclone5_socrates.
Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
Diffstat (limited to 'drivers/serial')
| -rw-r--r-- | drivers/serial/ns16550.c | 18 |
1 files changed, 16 insertions, 2 deletions
diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c index f9041aa626..04b604fa2c 100644 --- a/drivers/serial/ns16550.c +++ b/drivers/serial/ns16550.c @@ -267,12 +267,26 @@ static inline void _debug_uart_init(void) serial_dout(&com_port->lcr, UART_LCRVAL); } +static inline int NS16550_read_baud_divisor(struct NS16550 *com_port) +{ + int ret; + + serial_dout(&com_port->lcr, UART_LCR_BKSE | UART_LCRVAL); + ret = serial_din(&com_port->dll) & 0xff; + ret |= (serial_din(&com_port->dlm) & 0xff) << 8; + serial_dout(&com_port->lcr, UART_LCRVAL); + + return ret; +} + static inline void _debug_uart_putc(int ch) { struct NS16550 *com_port = (struct NS16550 *)CONFIG_DEBUG_UART_BASE; - while (!(serial_din(&com_port->lsr) & UART_LSR_THRE)) - ; + while (!(serial_din(&com_port->lsr) & UART_LSR_THRE)) { + if (!NS16550_read_baud_divisor(com_port)) + return; + } serial_dout(&com_port->thr, ch); } |