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serial: 8250: Defer interrupt enable until fifos enabled 

An already-active sender can swamp the interrupt handler with
"too much work" if the rx interrupts are enabled when the fifo is
disabled and operating in single-byte mode.

Defer rx and line status interrupt enable until after the fifos
are enabled in set_termios(), but at least initialize the shadow
IER value with the interrupts which will be enabled.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2015-07-12 21:11:31 -04:00 committed by Greg Kroah-Hartman
parent 45c6df4471
commit ee3ad90be5
1 changed files with 3 additions and 4 deletions
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7
drivers/tty/serial/8250/8250_port.c
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@ -2002,12 +2002,11 @@ dont_test_tx_en:
}
/*
* Finally, enable interrupts. Note: Modem status interrupts
* are set via set_termios(), which will be occurring imminently
* anyway, so we don't enable them here.
* Set the IER shadow for rx interrupts but defer actual interrupt
* enable until after the FIFOs are enabled; otherwise, an already-
* active sender can swamp the interrupt handler with "too much work".
*/
up->ier = UART_IER_RLSI | UART_IER_RDI;
serial_port_out(port, UART_IER, up->ier);
if (port->flags & UPF_FOURPORT) {
unsigned int icp;