1*9bef3d41SPaul Gortmaker #include <linux/serial_reg.h> 2*9bef3d41SPaul Gortmaker #include <linux/serial_8250.h> 3*9bef3d41SPaul Gortmaker 4*9bef3d41SPaul Gortmaker #include "8250.h" 5*9bef3d41SPaul Gortmaker 6*9bef3d41SPaul Gortmaker /* 7*9bef3d41SPaul Gortmaker * Freescale 16550 UART "driver", Copyright (C) 2011 Paul Gortmaker. 8*9bef3d41SPaul Gortmaker * 9*9bef3d41SPaul Gortmaker * This program is free software; you can redistribute it and/or modify 10*9bef3d41SPaul Gortmaker * it under the terms of the GNU General Public License version 2 as 11*9bef3d41SPaul Gortmaker * published by the Free Software Foundation. 12*9bef3d41SPaul Gortmaker * 13*9bef3d41SPaul Gortmaker * This isn't a full driver; it just provides an alternate IRQ 14*9bef3d41SPaul Gortmaker * handler to deal with an errata. Everything else is just 15*9bef3d41SPaul Gortmaker * using the bog standard 8250 support. 16*9bef3d41SPaul Gortmaker * 17*9bef3d41SPaul Gortmaker * We follow code flow of serial8250_default_handle_irq() but add 18*9bef3d41SPaul Gortmaker * a check for a break and insert a dummy read on the Rx for the 19*9bef3d41SPaul Gortmaker * immediately following IRQ event. 20*9bef3d41SPaul Gortmaker * 21*9bef3d41SPaul Gortmaker * We re-use the already existing "bug handling" lsr_saved_flags 22*9bef3d41SPaul Gortmaker * field to carry the "what we just did" information from the one 23*9bef3d41SPaul Gortmaker * IRQ event to the next one. 24*9bef3d41SPaul Gortmaker */ 25*9bef3d41SPaul Gortmaker 26*9bef3d41SPaul Gortmaker int fsl8250_handle_irq(struct uart_port *port) 27*9bef3d41SPaul Gortmaker { 28*9bef3d41SPaul Gortmaker unsigned char lsr, orig_lsr; 29*9bef3d41SPaul Gortmaker unsigned long flags; 30*9bef3d41SPaul Gortmaker unsigned int iir; 31*9bef3d41SPaul Gortmaker struct uart_8250_port *up = 32*9bef3d41SPaul Gortmaker container_of(port, struct uart_8250_port, port); 33*9bef3d41SPaul Gortmaker 34*9bef3d41SPaul Gortmaker spin_lock_irqsave(&up->port.lock, flags); 35*9bef3d41SPaul Gortmaker 36*9bef3d41SPaul Gortmaker iir = port->serial_in(port, UART_IIR); 37*9bef3d41SPaul Gortmaker if (iir & UART_IIR_NO_INT) { 38*9bef3d41SPaul Gortmaker spin_unlock_irqrestore(&up->port.lock, flags); 39*9bef3d41SPaul Gortmaker return 0; 40*9bef3d41SPaul Gortmaker } 41*9bef3d41SPaul Gortmaker 42*9bef3d41SPaul Gortmaker /* This is the WAR; if last event was BRK, then read and return */ 43*9bef3d41SPaul Gortmaker if (unlikely(up->lsr_saved_flags & UART_LSR_BI)) { 44*9bef3d41SPaul Gortmaker up->lsr_saved_flags &= ~UART_LSR_BI; 45*9bef3d41SPaul Gortmaker port->serial_in(port, UART_RX); 46*9bef3d41SPaul Gortmaker spin_unlock_irqrestore(&up->port.lock, flags); 47*9bef3d41SPaul Gortmaker return 1; 48*9bef3d41SPaul Gortmaker } 49*9bef3d41SPaul Gortmaker 50*9bef3d41SPaul Gortmaker lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR); 51*9bef3d41SPaul Gortmaker 52*9bef3d41SPaul Gortmaker if (lsr & (UART_LSR_DR | UART_LSR_BI)) 53*9bef3d41SPaul Gortmaker lsr = serial8250_rx_chars(up, lsr); 54*9bef3d41SPaul Gortmaker 55*9bef3d41SPaul Gortmaker serial8250_modem_status(up); 56*9bef3d41SPaul Gortmaker 57*9bef3d41SPaul Gortmaker if (lsr & UART_LSR_THRE) 58*9bef3d41SPaul Gortmaker serial8250_tx_chars(up); 59*9bef3d41SPaul Gortmaker 60*9bef3d41SPaul Gortmaker up->lsr_saved_flags = orig_lsr; 61*9bef3d41SPaul Gortmaker spin_unlock_irqrestore(&up->port.lock, flags); 62*9bef3d41SPaul Gortmaker return 1; 63*9bef3d41SPaul Gortmaker } 64