serial console
Mark Hahn
hahn at physics.mcmaster.ca
Tue Aug 20 08:24:55 PDT 2002
> console=ttyS0,9600n8r to my kernel parameters and nothing is connected to the
from a quick look at drivers/char/serial.c, 'r' results in the
ASYNC_CONS_FLOW tells it to wait for CTS:
static inline void wait_for_xmitr(struct async_struct *info)
{
unsigned int status, tmout = 1000000;
do {
status = serial_in(info, UART_LSR);
if (status & UART_LSR_BI)
lsr_break_flag = UART_LSR_BI;
if (--tmout == 0)
break;
} while((status & BOTH_EMPTY) != BOTH_EMPTY);
/* Wait for flow control if necessary */
if (info->flags & ASYNC_CONS_FLOW) {
tmout = 1000000;
while (--tmout &&
((serial_in(info, UART_MSR) & UART_MSR_CTS) == 0));
}
}
since one serial_in would take O(1us), I think each byte transmitted would
take about a second, rather than 1ms, which matches your symptoms...
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