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 } 63