Commit 68cb4f8e authored Nov 18, 2009 by Ian Jackson Committed by Greg Kroah-Hartman Dec 11, 2009

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 <ian.jackson@eu.citrix.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Jiri Kosina <jkosina@suse.cz>
Cc: Alan Cox <alan@linux.intel.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

parent 7e11a0fb

drivers/serial/8250.c

+3 −5

Original line number	Diff line number	Diff line
		@@ -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);
		}
		}

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