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Serial: Do not read IIR in serial8250_start_tx when UART_BUG_TXEN

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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>
This commit is contained in:
Ian Jackson 2009-11-18 11:08:11 +01:00 committed by Greg Kroah-Hartman
parent 7e11a0fb3b
commit 68cb4f8e24
1 changed files with 3 additions and 5 deletions
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8
drivers/serial/8250.c
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@ -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);
}
}