1 // SPDX-License-Identifier: GPL-2.0
2 #if defined(CONFIG_SERIAL_8250_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
3 #define SUPPORT_SYSRQ
4 #endif
5
6 #include <linux/serial_reg.h>
7 #include <linux/serial_8250.h>
8
9 #include "8250.h"
10
11 /*
12 * Freescale 16550 UART "driver", Copyright (C) 2011 Paul Gortmaker.
13 *
14 * This isn't a full driver; it just provides an alternate IRQ
15 * handler to deal with an errata. Everything else is just
16 * using the bog standard 8250 support.
17 *
18 * We follow code flow of serial8250_default_handle_irq() but add
19 * a check for a break and insert a dummy read on the Rx for the
20 * immediately following IRQ event.
21 *
22 * We re-use the already existing "bug handling" lsr_saved_flags
23 * field to carry the "what we just did" information from the one
24 * IRQ event to the next one.
25 */
26
fsl8250_handle_irq(struct uart_port * port)27 int fsl8250_handle_irq(struct uart_port *port)
28 {
29 unsigned char lsr, orig_lsr;
30 unsigned long flags;
31 unsigned int iir;
32 struct uart_8250_port *up = up_to_u8250p(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 /* Process incoming characters first */
53 if ((lsr & (UART_LSR_DR | UART_LSR_BI)) &&
54 (up->ier & (UART_IER_RLSI | UART_IER_RDI))) {
55 lsr = serial8250_rx_chars(up, lsr);
56 }
57
58 /* Stop processing interrupts on input overrun */
59 if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) {
60 unsigned long delay;
61
62 up->ier = port->serial_in(port, UART_IER);
63 if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) {
64 port->ops->stop_rx(port);
65 } else {
66 /* Keep restarting the timer until
67 * the input overrun subsides.
68 */
69 cancel_delayed_work(&up->overrun_backoff);
70 }
71
72 delay = msecs_to_jiffies(up->overrun_backoff_time_ms);
73 schedule_delayed_work(&up->overrun_backoff, delay);
74 }
75
76 serial8250_modem_status(up);
77
78 if (lsr & UART_LSR_THRE)
79 serial8250_tx_chars(up);
80
81 up->lsr_saved_flags = orig_lsr;
82 uart_unlock_and_check_sysrq(&up->port, flags);
83 return 1;
84 }
85 EXPORT_SYMBOL_GPL(fsl8250_handle_irq);
86
