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serial: 8250: Use frame time to determine timeout

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Rather than using a hard-coded per-character Tx-timeout of 10ms,
use the frame time to determine a timeout value. The value is
doubled to ensure that a timeout is only hit during unexpected
circumstances.

Since the frame time may not be available during early printing,
the previous 10ms value is kept as a fallback.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20250107212702.169493-3-john.ogness@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
John Ogness 2025-01-07 22:32:58 +01:06 committed by Greg Kroah-Hartman
parent d91f98be26
commit 8d5cfb1fe5
1 changed files with 10 additions and 2 deletions
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12
drivers/tty/serial/8250/8250_port.c
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@ -2081,9 +2081,17 @@ static void serial8250_break_ctl(struct uart_port *port, int break_state)
/* Returns true if @bits were set, false on timeout */
static bool wait_for_lsr(struct uart_8250_port *up, int bits)
{
unsigned int status, tmout = 10000;
unsigned int status, tmout;
/*
* Wait for a character to be sent. Fallback to a safe default
* timeout value if @frame_time is not available.
*/
if (up->port.frame_time)
tmout = up->port.frame_time * 2 / NSEC_PER_USEC;
else
tmout = 10000;
/* Wait up to 10ms for the character(s) to be sent. */
for (;;) {
status = serial_lsr_in(up);