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authorSimon Goldschmidt2018-08-09 14:04:19 -0500
committerSimon Glass2018-11-14 11:16:28 -0600
commit6f57c34473d37b8da5e6a3764d0d377d748aeef1 (patch)
treed6ab8dab8076d0dc5e7f7ad64b7d8dfb9be7a025 /drivers
parent81f351d6e7ebb371de8ea849fc21dd07dc2eff24 (diff)
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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')
-rw-r--r--drivers/serial/ns16550.c18
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)
267 serial_dout(&com_port->lcr, UART_LCRVAL); 267 serial_dout(&com_port->lcr, UART_LCRVAL);
268} 268}
269 269
270static inline int NS16550_read_baud_divisor(struct NS16550 *com_port)
271{
272 int ret;
273
274 serial_dout(&com_port->lcr, UART_LCR_BKSE | UART_LCRVAL);
275 ret = serial_din(&com_port->dll) & 0xff;
276 ret |= (serial_din(&com_port->dlm) & 0xff) << 8;
277 serial_dout(&com_port->lcr, UART_LCRVAL);
278
279 return ret;
280}
281
270static inline void _debug_uart_putc(int ch) 282static inline void _debug_uart_putc(int ch)
271{ 283{
272 struct NS16550 *com_port = (struct NS16550 *)CONFIG_DEBUG_UART_BASE; 284 struct NS16550 *com_port = (struct NS16550 *)CONFIG_DEBUG_UART_BASE;
273 285
274 while (!(serial_din(&com_port->lsr) & UART_LSR_THRE)) 286 while (!(serial_din(&com_port->lsr) & UART_LSR_THRE)) {
275 ; 287 if (!NS16550_read_baud_divisor(com_port))
288 return;
289 }
276 serial_dout(&com_port->thr, ch); 290 serial_dout(&com_port->thr, ch);
277} 291}
278 292