1*e3b3d0f5SGreg Kroah-Hartman // SPDX-License-Identifier: GPL-2.0 29bef3d41SPaul Gortmaker #include <linux/serial_reg.h> 39bef3d41SPaul Gortmaker #include <linux/serial_8250.h> 49bef3d41SPaul Gortmaker 59bef3d41SPaul Gortmaker #include "8250.h" 69bef3d41SPaul Gortmaker 79bef3d41SPaul Gortmaker /* 89bef3d41SPaul Gortmaker * Freescale 16550 UART "driver", Copyright (C) 2011 Paul Gortmaker. 99bef3d41SPaul Gortmaker * 109bef3d41SPaul Gortmaker * This program is free software; you can redistribute it and/or modify 119bef3d41SPaul Gortmaker * it under the terms of the GNU General Public License version 2 as 129bef3d41SPaul Gortmaker * published by the Free Software Foundation. 139bef3d41SPaul Gortmaker * 149bef3d41SPaul Gortmaker * This isn't a full driver; it just provides an alternate IRQ 159bef3d41SPaul Gortmaker * handler to deal with an errata. Everything else is just 169bef3d41SPaul Gortmaker * using the bog standard 8250 support. 179bef3d41SPaul Gortmaker * 189bef3d41SPaul Gortmaker * We follow code flow of serial8250_default_handle_irq() but add 199bef3d41SPaul Gortmaker * a check for a break and insert a dummy read on the Rx for the 209bef3d41SPaul Gortmaker * immediately following IRQ event. 219bef3d41SPaul Gortmaker * 229bef3d41SPaul Gortmaker * We re-use the already existing "bug handling" lsr_saved_flags 239bef3d41SPaul Gortmaker * field to carry the "what we just did" information from the one 249bef3d41SPaul Gortmaker * IRQ event to the next one. 259bef3d41SPaul Gortmaker */ 269bef3d41SPaul Gortmaker 279bef3d41SPaul Gortmaker int fsl8250_handle_irq(struct uart_port *port) 289bef3d41SPaul Gortmaker { 299bef3d41SPaul Gortmaker unsigned char lsr, orig_lsr; 309bef3d41SPaul Gortmaker unsigned long flags; 319bef3d41SPaul Gortmaker unsigned int iir; 32b1261c86SAndy Shevchenko struct uart_8250_port *up = up_to_u8250p(port); 339bef3d41SPaul Gortmaker 349bef3d41SPaul Gortmaker spin_lock_irqsave(&up->port.lock, flags); 359bef3d41SPaul Gortmaker 369bef3d41SPaul Gortmaker iir = port->serial_in(port, UART_IIR); 379bef3d41SPaul Gortmaker if (iir & UART_IIR_NO_INT) { 389bef3d41SPaul Gortmaker spin_unlock_irqrestore(&up->port.lock, flags); 399bef3d41SPaul Gortmaker return 0; 409bef3d41SPaul Gortmaker } 419bef3d41SPaul Gortmaker 429bef3d41SPaul Gortmaker /* This is the WAR; if last event was BRK, then read and return */ 439bef3d41SPaul Gortmaker if (unlikely(up->lsr_saved_flags & UART_LSR_BI)) { 449bef3d41SPaul Gortmaker up->lsr_saved_flags &= ~UART_LSR_BI; 459bef3d41SPaul Gortmaker port->serial_in(port, UART_RX); 469bef3d41SPaul Gortmaker spin_unlock_irqrestore(&up->port.lock, flags); 479bef3d41SPaul Gortmaker return 1; 489bef3d41SPaul Gortmaker } 499bef3d41SPaul Gortmaker 509bef3d41SPaul Gortmaker lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR); 519bef3d41SPaul Gortmaker 529bef3d41SPaul Gortmaker if (lsr & (UART_LSR_DR | UART_LSR_BI)) 539bef3d41SPaul Gortmaker lsr = serial8250_rx_chars(up, lsr); 549bef3d41SPaul Gortmaker 559bef3d41SPaul Gortmaker serial8250_modem_status(up); 569bef3d41SPaul Gortmaker 579bef3d41SPaul Gortmaker if (lsr & UART_LSR_THRE) 589bef3d41SPaul Gortmaker serial8250_tx_chars(up); 599bef3d41SPaul Gortmaker 609bef3d41SPaul Gortmaker up->lsr_saved_flags = orig_lsr; 619bef3d41SPaul Gortmaker spin_unlock_irqrestore(&up->port.lock, flags); 629bef3d41SPaul Gortmaker return 1; 639bef3d41SPaul Gortmaker } 64bd63acf9SArnd Bergmann EXPORT_SYMBOL_GPL(fsl8250_handle_irq); 65