The patch below has been lost several times (the last submission happened probably on [1]). I am currently aware of a real hardware which triggers this problem quite reliably, so we should rather have that really fixed. [1] http://lkml.org/lkml/2009/3/12/379 From: Ian Jackson <ian.jackson@xxxxxxxxxxxxx> Do not read IIR in serial8250_start_tx when UART_BUG_TXEN Reading the IIR clears some oustanding interrupts so it is not safe. Instead, simply transmit immediately if the buffer is empty without regard to IIR. Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx> Reviewed-by: Markus Armbruster <armbru@xxxxxxxxxx> Reviewed-by: Jiri Kosina <jkosina@xxxxxxx> --- drivers/serial/8250.c | 8 +++----- 1 files changed, 3 insertions(+), 5 deletions(-) diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c index 737b4c9..807042b 100644 --- a/drivers/serial/8250.c +++ b/drivers/serial/8250.c @@ -1339,14 +1339,12 @@ static void serial8250_start_tx(struct uart_port *port) serial_out(up, UART_IER, up->ier); if (up->bugs & UART_BUG_TXEN) { - unsigned char lsr, iir; + unsigned char lsr; lsr = serial_in(up, UART_LSR); up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS; - iir = serial_in(up, UART_IIR) & 0x0f; if ((up->port.type == PORT_RM9000) ? - (lsr & UART_LSR_THRE && - (iir == UART_IIR_NO_INT || iir == UART_IIR_THRI)) : - (lsr & UART_LSR_TEMT && iir & UART_IIR_NO_INT)) + (lsr & UART_LSR_THRE) : + (lsr & UART_LSR_TEMT)) transmit_chars(up); } } -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
