From 68cb4f8e246bbbc649980be0628cae9265870a91 Mon Sep 17 00:00:00 2001 From: Ian Jackson Date: Wed, 18 Nov 2009 11:08:11 +0100 Subject: [PATCH] Serial: Do not read IIR in serial8250_start_tx when UART_BUG_TXEN 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 Reviewed-by: Markus Armbruster Reviewed-by: Jiri Kosina Cc: Alan Cox Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/serial/8250.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c index b75e63e9d1e..c3e37c8e7e2 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); } } -- 2.20.1