// SPDX-License-Identifier: GPL-2.0
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#include <linux/serial_reg.h>
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#include <linux/serial_8250.h>
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#include "8250.h"
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/*
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* Freescale 16550 UART "driver", Copyright (C) 2011 Paul Gortmaker.
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*
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* This isn't a full driver; it just provides an alternate IRQ
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* handler to deal with an errata. Everything else is just
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* using the bog standard 8250 support.
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*
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* We follow code flow of serial8250_default_handle_irq() but add
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* a check for a break and insert a dummy read on the Rx for the
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* immediately following IRQ event.
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*
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* We re-use the already existing "bug handling" lsr_saved_flags
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* field to carry the "what we just did" information from the one
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* IRQ event to the next one.
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*/
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int fsl8250_handle_irq(struct uart_port *port)
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{
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unsigned char lsr, orig_lsr;
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unsigned long flags;
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unsigned int iir;
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struct uart_8250_port *up = up_to_u8250p(port);
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spin_lock_irqsave(&up->port.lock, flags);
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iir = port->serial_in(port, UART_IIR);
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if (iir & UART_IIR_NO_INT) {
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spin_unlock_irqrestore(&up->port.lock, flags);
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return 0;
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}
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/* This is the WAR; if last event was BRK, then read and return */
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if (unlikely(up->lsr_saved_flags & UART_LSR_BI)) {
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up->lsr_saved_flags &= ~UART_LSR_BI;
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port->serial_in(port, UART_RX);
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spin_unlock_irqrestore(&up->port.lock, flags);
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return 1;
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}
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lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR);
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/* Process incoming characters first */
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if ((lsr & (UART_LSR_DR | UART_LSR_BI)) &&
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(up->ier & (UART_IER_RLSI | UART_IER_RDI))) {
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lsr = serial8250_rx_chars(up, lsr);
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}
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/* Stop processing interrupts on input overrun */
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if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) {
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unsigned long delay;
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up->ier = port->serial_in(port, UART_IER);
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if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) {
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port->ops->stop_rx(port);
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} else {
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/* Keep restarting the timer until
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* the input overrun subsides.
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*/
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cancel_delayed_work(&up->overrun_backoff);
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}
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delay = msecs_to_jiffies(up->overrun_backoff_time_ms);
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schedule_delayed_work(&up->overrun_backoff, delay);
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}
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serial8250_modem_status(up);
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if (lsr & UART_LSR_THRE)
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serial8250_tx_chars(up);
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up->lsr_saved_flags = orig_lsr;
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spin_unlock_irqrestore(&up->port.lock, flags);
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return 1;
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}
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EXPORT_SYMBOL_GPL(fsl8250_handle_irq);
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