1 #include <linux/serial_reg.h>
2 #include <linux/serial_8250.h>
3
4 #include "8250.h"
5
6 /*
7 * Freescale 16550 UART "driver", Copyright (C) 2011 Paul Gortmaker.
8 *
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.
12 *
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.
16 *
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.
20 *
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.
24 */
25
fsl8250_handle_irq(struct uart_port * port)26 int fsl8250_handle_irq(struct uart_port *port)
27 {
28 unsigned char lsr, orig_lsr;
29 unsigned long flags;
30 unsigned int iir;
31 struct uart_8250_port *up =
32 container_of(port, struct uart_8250_port, port);
33
34 spin_lock_irqsave(&up->port.lock, flags);
35
36 iir = port->serial_in(port, UART_IIR);
37 if (iir & UART_IIR_NO_INT) {
38 spin_unlock_irqrestore(&up->port.lock, flags);
39 return 0;
40 }
41
42 /* This is the WAR; if last event was BRK, then read and return */
43 if (unlikely(up->lsr_saved_flags & UART_LSR_BI)) {
44 up->lsr_saved_flags &= ~UART_LSR_BI;
45 port->serial_in(port, UART_RX);
46 spin_unlock_irqrestore(&up->port.lock, flags);
47 return 1;
48 }
49
50 lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR);
51
52 if (lsr & (UART_LSR_DR | UART_LSR_BI))
53 lsr = serial8250_rx_chars(up, lsr);
54
55 serial8250_modem_status(up);
56
57 if (lsr & UART_LSR_THRE)
58 serial8250_tx_chars(up);
59
60 up->lsr_saved_flags = orig_lsr;
61 spin_unlock_irqrestore(&up->port.lock, flags);
62 return 1;
63 }
64