1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Freescale 16550 UART "driver", Copyright (C) 2011 Paul Gortmaker. 4 * Copyright 2020 NXP 5 * Copyright 2020 Puresoftware Ltd. 6 * 7 * This isn't a full driver; it just provides an alternate IRQ 8 * handler to deal with an errata and provide ACPI wrapper. 9 * Everything else is just using the bog standard 8250 support. 10 * 11 * We follow code flow of serial8250_default_handle_irq() but add 12 * a check for a break and insert a dummy read on the Rx for the 13 * immediately following IRQ event. 14 * 15 * We re-use the already existing "bug handling" lsr_saved_flags 16 * field to carry the "what we just did" information from the one 17 * IRQ event to the next one. 18 */ 19 20 #include <linux/acpi.h> 21 #include <linux/serial_reg.h> 22 #include <linux/serial_8250.h> 23 24 #include "8250.h" 25 26 struct fsl8250_data { 27 int line; 28 }; 29 30 int fsl8250_handle_irq(struct uart_port *port) 31 { 32 unsigned char lsr, orig_lsr; 33 unsigned int iir; 34 struct uart_8250_port *up = up_to_u8250p(port); 35 36 spin_lock(&up->port.lock); 37 38 iir = port->serial_in(port, UART_IIR); 39 if (iir & UART_IIR_NO_INT) { 40 spin_unlock(&up->port.lock); 41 return 0; 42 } 43 44 /* This is the WAR; if last event was BRK, then read and return */ 45 if (unlikely(up->lsr_saved_flags & UART_LSR_BI)) { 46 up->lsr_saved_flags &= ~UART_LSR_BI; 47 port->serial_in(port, UART_RX); 48 spin_unlock(&up->port.lock); 49 return 1; 50 } 51 52 lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR); 53 54 /* Process incoming characters first */ 55 if ((lsr & (UART_LSR_DR | UART_LSR_BI)) && 56 (up->ier & (UART_IER_RLSI | UART_IER_RDI))) { 57 lsr = serial8250_rx_chars(up, lsr); 58 } 59 60 /* Stop processing interrupts on input overrun */ 61 if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) { 62 unsigned long delay; 63 64 up->ier = port->serial_in(port, UART_IER); 65 if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) { 66 port->ops->stop_rx(port); 67 } else { 68 /* Keep restarting the timer until 69 * the input overrun subsides. 70 */ 71 cancel_delayed_work(&up->overrun_backoff); 72 } 73 74 delay = msecs_to_jiffies(up->overrun_backoff_time_ms); 75 schedule_delayed_work(&up->overrun_backoff, delay); 76 } 77 78 serial8250_modem_status(up); 79 80 if ((lsr & UART_LSR_THRE) && (up->ier & UART_IER_THRI)) 81 serial8250_tx_chars(up); 82 83 up->lsr_saved_flags = orig_lsr; 84 85 uart_unlock_and_check_sysrq(&up->port); 86 87 return 1; 88 } 89 EXPORT_SYMBOL_GPL(fsl8250_handle_irq); 90 91 #ifdef CONFIG_ACPI 92 static int fsl8250_acpi_probe(struct platform_device *pdev) 93 { 94 struct fsl8250_data *data; 95 struct uart_8250_port port8250; 96 struct device *dev = &pdev->dev; 97 struct resource *regs; 98 99 int ret, irq; 100 101 regs = platform_get_resource(pdev, IORESOURCE_MEM, 0); 102 if (!regs) { 103 dev_err(dev, "no registers defined\n"); 104 return -EINVAL; 105 } 106 107 irq = platform_get_irq(pdev, 0); 108 if (irq < 0) 109 return irq; 110 111 memset(&port8250, 0, sizeof(port8250)); 112 113 ret = device_property_read_u32(dev, "clock-frequency", 114 &port8250.port.uartclk); 115 if (ret) 116 return ret; 117 118 spin_lock_init(&port8250.port.lock); 119 120 port8250.port.mapbase = regs->start; 121 port8250.port.irq = irq; 122 port8250.port.handle_irq = fsl8250_handle_irq; 123 port8250.port.type = PORT_16550A; 124 port8250.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF 125 | UPF_FIXED_PORT | UPF_IOREMAP 126 | UPF_FIXED_TYPE; 127 port8250.port.dev = dev; 128 port8250.port.mapsize = resource_size(regs); 129 port8250.port.iotype = UPIO_MEM; 130 port8250.port.irqflags = IRQF_SHARED; 131 132 port8250.port.membase = devm_ioremap(dev, port8250.port.mapbase, 133 port8250.port.mapsize); 134 if (!port8250.port.membase) 135 return -ENOMEM; 136 137 data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL); 138 if (!data) 139 return -ENOMEM; 140 141 data->line = serial8250_register_8250_port(&port8250); 142 if (data->line < 0) 143 return data->line; 144 145 platform_set_drvdata(pdev, data); 146 return 0; 147 } 148 149 static int fsl8250_acpi_remove(struct platform_device *pdev) 150 { 151 struct fsl8250_data *data = platform_get_drvdata(pdev); 152 153 serial8250_unregister_port(data->line); 154 return 0; 155 } 156 157 static const struct acpi_device_id fsl_8250_acpi_id[] = { 158 { "NXP0018", 0 }, 159 { }, 160 }; 161 MODULE_DEVICE_TABLE(acpi, fsl_8250_acpi_id); 162 163 static struct platform_driver fsl8250_platform_driver = { 164 .driver = { 165 .name = "fsl-16550-uart", 166 .acpi_match_table = ACPI_PTR(fsl_8250_acpi_id), 167 }, 168 .probe = fsl8250_acpi_probe, 169 .remove = fsl8250_acpi_remove, 170 }; 171 172 module_platform_driver(fsl8250_platform_driver); 173 #endif 174