1 #include <linux/serial_reg.h>
2 #include <linux/serial_8250.h>
7 * Freescale 16550 UART "driver", Copyright (C) 2011 Paul Gortmaker.
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License version 2 as
11 * published by the Free Software Foundation.
13 * This isn't a full driver; it just provides an alternate IRQ
14 * handler to deal with an errata. Everything else is just
15 * using the bog standard 8250 support.
17 * We follow code flow of serial8250_default_handle_irq() but add
18 * a check for a break and insert a dummy read on the Rx for the
19 * immediately following IRQ event.
21 * We re-use the already existing "bug handling" lsr_saved_flags
22 * field to carry the "what we just did" information from the one
23 * IRQ event to the next one.
26 int fsl8250_handle_irq(struct uart_port *port)
28 unsigned char lsr, orig_lsr;
31 struct uart_8250_port *up = up_to_u8250p(port);
33 spin_lock_irqsave(&up->port.lock, flags);
35 iir = port->serial_in(port, UART_IIR);
36 if (iir & UART_IIR_NO_INT) {
37 spin_unlock_irqrestore(&up->port.lock, flags);
41 /* This is the WAR; if last event was BRK, then read and return */
42 if (unlikely(up->lsr_saved_flags & UART_LSR_BI)) {
43 up->lsr_saved_flags &= ~UART_LSR_BI;
44 port->serial_in(port, UART_RX);
45 spin_unlock_irqrestore(&up->port.lock, flags);
49 lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR);
51 /* Process incoming characters first */
52 if ((lsr & (UART_LSR_DR | UART_LSR_BI)) &&
53 (up->ier & (UART_IER_RLSI | UART_IER_RDI))) {
54 lsr = serial8250_rx_chars(up, lsr);
57 /* Stop processing interrupts on input overrun */
58 if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) {
61 up->ier = port->serial_in(port, UART_IER);
62 if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) {
63 port->ops->stop_rx(port);
65 /* Keep restarting the timer until
66 * the input overrun subsides.
68 cancel_delayed_work(&up->overrun_backoff);
71 delay = msecs_to_jiffies(up->overrun_backoff_time_ms);
72 schedule_delayed_work(&up->overrun_backoff, delay);
75 serial8250_modem_status(up);
77 if (lsr & UART_LSR_THRE)
78 serial8250_tx_chars(up);
80 up->lsr_saved_flags = orig_lsr;
81 spin_unlock_irqrestore(&up->port.lock, flags);
84 EXPORT_SYMBOL_GPL(fsl8250_handle_irq);