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 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