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A long cable attached to the UART can act as an antenna if disconnected from the other end. This can cause noise on the receive side, possibly as reflections from the transmit side, leading to an interrupt storm. Filter this by adding a threshold of received characters without TX ready, above which characters are dropped. This is disabled by default, but has been tested with a threshold of 1000+. A high threshold is recommended to avoid dropping characters during, for instance, a large copy/paste from the other end. Sponsored by: Juniper Networks, Inc.
64 lines
2.3 KiB
C
64 lines
2.3 KiB
C
/*-
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* SPDX-License-Identifier: BSD-2-Clause
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*
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* Copyright (c) 2003 Marcel Moolenaar
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef _DEV_UART_DEV_NS8250_H_
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#define _DEV_UART_DEV_NS8250_H_
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/*
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* High-level UART interface.
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*/
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struct ns8250_softc {
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struct uart_softc base;
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uint8_t fcr;
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uint8_t ier;
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uint8_t mcr;
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uint8_t ier_mask;
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uint8_t ier_rxbits;
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uint8_t busy_detect;
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int noise_count;
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};
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extern struct uart_ops uart_ns8250_ops;
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int ns8250_bus_attach(struct uart_softc *);
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int ns8250_bus_detach(struct uart_softc *);
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int ns8250_bus_flush(struct uart_softc *, int);
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int ns8250_bus_getsig(struct uart_softc *);
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int ns8250_bus_ioctl(struct uart_softc *, int, intptr_t);
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int ns8250_bus_ipend(struct uart_softc *);
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int ns8250_bus_param(struct uart_softc *, int, int, int, int);
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int ns8250_bus_probe(struct uart_softc *);
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int ns8250_bus_receive(struct uart_softc *);
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int ns8250_bus_setsig(struct uart_softc *, int);
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int ns8250_bus_transmit(struct uart_softc *);
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void ns8250_bus_grab(struct uart_softc *);
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bool ns8250_bus_txbusy(struct uart_softc *);
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void ns8250_bus_ungrab(struct uart_softc *);
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#endif /* _DEV_UART_DEV_NS8250_H_ */
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