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Commit ea5244e2 authored by Joel Stanley's avatar Joel Stanley Committed by Greg Kroah-Hartman
Browse files

serial: 8250: Add flag so drivers can avoid THRE probe 



The probing of THRE irq behaviour assumes the other end will be reading
bytes out of the buffer in order to probe the port at driver init. In
some cases the other end cannot be relied upon to read these bytes, so
provide a flag for them to skip this step.

Bit 19 was chosen as the flags are a int and the top bits are taken.

Acked-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: default avatarJoel Stanley <joel@jms.id.au>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 70b2fe35

drivers/tty/serial/8250/8250_port.c

+1 −1
Original line number Diff line number Diff line
@@ -2229,7 +2229,7 @@ int serial8250_do_startup(struct uart_port *port) 
		}

	}



	if (port->irq) {

	if (port->irq && !(up->port.flags & UPF_NO_THRE_TEST)) {

		unsigned char iir1;

		/*

		 * Test for UARTs that do not reassert THRE when the

include/linux/serial_core.h

+1 −0
Original line number Diff line number Diff line
@@ -195,6 +195,7 @@ struct uart_port { 
#define UPF_NO_TXEN_TEST	((__force upf_t) (1 << 15))

#define UPF_MAGIC_MULTIPLIER	((__force upf_t) ASYNC_MAGIC_MULTIPLIER /* 16 */ )



#define UPF_NO_THRE_TEST	((__force upf_t) (1 << 19))

/* Port has hardware-assisted h/w flow control */

#define UPF_AUTO_CTS		((__force upf_t) (1 << 20))

#define UPF_AUTO_RTS		((__force upf_t) (1 << 21))