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