diff options
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/serial/Kconfig | 12 | ||||
| -rw-r--r-- | drivers/serial/ns16550.c | 20 |
2 files changed, 30 insertions, 2 deletions
diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig index e67ea52338..887cd687c0 100644 --- a/drivers/serial/Kconfig +++ b/drivers/serial/Kconfig @@ -447,6 +447,18 @@ config DEBUG_UART_SKIP_INIT Select this if the UART you want to use for debug output is already initialized by the time U-Boot starts its execution. +config DEBUG_UART_NS16550_CHECK_ENABLED + bool "Check if UART is enabled on output" + depends on DEBUG_UART + depends on DEBUG_UART_NS16550 + help + Select this if puts()/putc() might be called before the debug UART + has been initialized. If this is disabled, putc() might sit in a + tight loop if it is called before debug_uart_init() has been called. + + Note that this does not work for every ns16550-compatible UART and + so has to be enabled carefully or you might notice lost characters. + config ALTERA_JTAG_UART bool "Altera JTAG UART support" depends on DM_SERIAL diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c index 560ca2ae34..6cf2be8f2b 100644 --- a/drivers/serial/ns16550.c +++ b/drivers/serial/ns16550.c @@ -272,12 +272,28 @@ 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)) { +#ifdef CONFIG_DEBUG_UART_NS16550_CHECK_ENABLED + if (!NS16550_read_baud_divisor(com_port)) + return; +#endif + } serial_dout(&com_port->thr, ch); } |