drivers/tty/serial/8250/8250_fsl.c

   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
  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 = up_to_u8250p(port);
  32
  33         spin_lock_irqsave(&up->port.lock, flags);
  34
  35         iir = port->serial_in(port, UART_IIR);
  36         if (iir & UART_IIR_NO_INT) {
  37                 spin_unlock_irqrestore(&up->port.lock, flags);
  38                 return 0;
  39         }
  40
  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);
  46                 return 1;
  47         }
  48
  49         lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR);
  50
  51         if (lsr & (UART_LSR_DR | UART_LSR_BI))
  52                 lsr = serial8250_rx_chars(up, lsr);
  53
  54         serial8250_modem_status(up);
  55
  56         if (lsr & UART_LSR_THRE)
  57                 serial8250_tx_chars(up);
  58
  59         up->lsr_saved_flags = orig_lsr;
  60         spin_unlock_irqrestore(&up->port.lock, flags);
  61         return 1;
  62 }