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 int fsl8250_handle_irq(struct uart_port *port) 27 { 28 unsigned long flags; 29 u16 lsr, orig_lsr; 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(&up->port.lock); 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(&up->port.lock); 46 return 1; 47 } 48 49 lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR); 50 51 /* Process incoming characters first */ 52 if ((lsr & (UART_LSR_DR | UART_LSR_BI)) && 53 (up->ier & (UART_IER_RLSI | UART_IER_RDI))) { 54 lsr = serial8250_rx_chars(up, lsr); 55 } 56 57 /* Stop processing interrupts on input overrun */ 58 if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) { 59 unsigned long delay; 60 61 up->ier = port->serial_in(port, UART_IER); 62 if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) { 63 port->ops->stop_rx(port); 64 } else { 65 /* Keep restarting the timer until 66 * the input overrun subsides. 67 */ 68 cancel_delayed_work(&up->overrun_backoff); 69 } 70 71 delay = msecs_to_jiffies(up->overrun_backoff_time_ms); 72 schedule_delayed_work(&up->overrun_backoff, delay); 73 } 74 75 serial8250_modem_status(up); 76 77 if ((lsr & UART_LSR_THRE) && (up->ier & UART_IER_THRI)) 78 serial8250_tx_chars(up); 79 80 up->lsr_saved_flags |= orig_lsr & UART_LSR_BI; 81 82 uart_unlock_and_check_sysrq_irqrestore(&up->port, flags); 83 84 return 1; 85 } 86 EXPORT_SYMBOL_GPL(fsl8250_handle_irq); 87 88 #ifdef CONFIG_ACPI 89 struct fsl8250_data { 90 int line; 91 }; 92 93 static int fsl8250_acpi_probe(struct platform_device *pdev) 94 { 95 struct fsl8250_data *data; 96 struct uart_8250_port port8250; 97 struct device *dev = &pdev->dev; 98 struct resource *regs; 99 100 int ret, irq; 101 102 regs = platform_get_resource(pdev, IORESOURCE_MEM, 0); 103 if (!regs) { 104 dev_err(dev, "no registers defined\n"); 105 return -EINVAL; 106 } 107 108 irq = platform_get_irq(pdev, 0); 109 if (irq < 0) 110 return irq; 111 112 memset(&port8250, 0, sizeof(port8250)); 113 114 ret = device_property_read_u32(dev, "clock-frequency", 115 &port8250.port.uartclk); 116 if (ret) 117 return ret; 118 119 spin_lock_init(&port8250.port.lock); 120 121 port8250.port.mapbase = regs->start; 122 port8250.port.irq = irq; 123 port8250.port.handle_irq = fsl8250_handle_irq; 124 port8250.port.type = PORT_16550A; 125 port8250.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF 126 | UPF_FIXED_PORT | UPF_IOREMAP 127 | UPF_FIXED_TYPE; 128 port8250.port.dev = dev; 129 port8250.port.mapsize = resource_size(regs); 130 port8250.port.iotype = UPIO_MEM; 131 port8250.port.irqflags = IRQF_SHARED; 132 133 port8250.port.membase = devm_ioremap(dev, port8250.port.mapbase, 134 port8250.port.mapsize); 135 if (!port8250.port.membase) 136 return -ENOMEM; 137 138 data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL); 139 if (!data) 140 return -ENOMEM; 141 142 data->line = serial8250_register_8250_port(&port8250); 143 if (data->line < 0) 144 return data->line; 145 146 platform_set_drvdata(pdev, data); 147 return 0; 148 } 149 150 static int fsl8250_acpi_remove(struct platform_device *pdev) 151 { 152 struct fsl8250_data *data = platform_get_drvdata(pdev); 153 154 serial8250_unregister_port(data->line); 155 return 0; 156 } 157 158 static const struct acpi_device_id fsl_8250_acpi_id[] = { 159 { "NXP0018", 0 }, 160 { }, 161 }; 162 MODULE_DEVICE_TABLE(acpi, fsl_8250_acpi_id); 163 164 static struct platform_driver fsl8250_platform_driver = { 165 .driver = { 166 .name = "fsl-16550-uart", 167 .acpi_match_table = ACPI_PTR(fsl_8250_acpi_id), 168 }, 169 .probe = fsl8250_acpi_probe, 170 .remove = fsl8250_acpi_remove, 171 }; 172 173 module_platform_driver(fsl8250_platform_driver); 174 #endif 175