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 long flags; 34 unsigned int iir; 35 struct uart_8250_port *up = up_to_u8250p(port); 36 37 spin_lock_irqsave(&up->port.lock, flags); 38 39 iir = port->serial_in(port, UART_IIR); 40 if (iir & UART_IIR_NO_INT) { 41 spin_unlock_irqrestore(&up->port.lock, flags); 42 return 0; 43 } 44 45 /* This is the WAR; if last event was BRK, then read and return */ 46 if (unlikely(up->lsr_saved_flags & UART_LSR_BI)) { 47 up->lsr_saved_flags &= ~UART_LSR_BI; 48 port->serial_in(port, UART_RX); 49 spin_unlock_irqrestore(&up->port.lock, flags); 50 return 1; 51 } 52 53 lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR); 54 55 /* Process incoming characters first */ 56 if ((lsr & (UART_LSR_DR | UART_LSR_BI)) && 57 (up->ier & (UART_IER_RLSI | UART_IER_RDI))) { 58 lsr = serial8250_rx_chars(up, lsr); 59 } 60 61 /* Stop processing interrupts on input overrun */ 62 if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) { 63 unsigned long delay; 64 65 up->ier = port->serial_in(port, UART_IER); 66 if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) { 67 port->ops->stop_rx(port); 68 } else { 69 /* Keep restarting the timer until 70 * the input overrun subsides. 71 */ 72 cancel_delayed_work(&up->overrun_backoff); 73 } 74 75 delay = msecs_to_jiffies(up->overrun_backoff_time_ms); 76 schedule_delayed_work(&up->overrun_backoff, delay); 77 } 78 79 serial8250_modem_status(up); 80 81 if ((lsr & UART_LSR_THRE) && (up->ier & UART_IER_THRI)) 82 serial8250_tx_chars(up); 83 84 up->lsr_saved_flags = orig_lsr; 85 uart_unlock_and_check_sysrq(&up->port, flags); 86 return 1; 87 } 88 EXPORT_SYMBOL_GPL(fsl8250_handle_irq); 89 90 #ifdef CONFIG_ACPI 91 static int fsl8250_acpi_probe(struct platform_device *pdev) 92 { 93 struct fsl8250_data *data; 94 struct uart_8250_port port8250; 95 struct device *dev = &pdev->dev; 96 struct resource *regs; 97 98 int ret, irq; 99 100 regs = platform_get_resource(pdev, IORESOURCE_MEM, 0); 101 if (!regs) { 102 dev_err(dev, "no registers defined\n"); 103 return -EINVAL; 104 } 105 106 irq = platform_get_irq(pdev, 0); 107 if (irq < 0) { 108 if (irq != -EPROBE_DEFER) 109 dev_err(dev, "cannot get irq\n"); 110 return irq; 111 } 112 113 memset(&port8250, 0, sizeof(port8250)); 114 115 ret = device_property_read_u32(dev, "clock-frequency", 116 &port8250.port.uartclk); 117 if (ret) 118 return ret; 119 120 spin_lock_init(&port8250.port.lock); 121 122 port8250.port.mapbase = regs->start; 123 port8250.port.irq = irq; 124 port8250.port.handle_irq = fsl8250_handle_irq; 125 port8250.port.type = PORT_16550A; 126 port8250.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF 127 | UPF_FIXED_PORT | UPF_IOREMAP 128 | UPF_FIXED_TYPE; 129 port8250.port.dev = dev; 130 port8250.port.mapsize = resource_size(regs); 131 port8250.port.iotype = UPIO_MEM; 132 port8250.port.irqflags = IRQF_SHARED; 133 134 port8250.port.membase = devm_ioremap(dev, port8250.port.mapbase, 135 port8250.port.mapsize); 136 if (!port8250.port.membase) 137 return -ENOMEM; 138 139 data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL); 140 if (!data) 141 return -ENOMEM; 142 143 data->line = serial8250_register_8250_port(&port8250); 144 if (data->line < 0) 145 return data->line; 146 147 platform_set_drvdata(pdev, data); 148 return 0; 149 } 150 151 static int fsl8250_acpi_remove(struct platform_device *pdev) 152 { 153 struct fsl8250_data *data = platform_get_drvdata(pdev); 154 155 serial8250_unregister_port(data->line); 156 return 0; 157 } 158 159 static const struct acpi_device_id fsl_8250_acpi_id[] = { 160 { "NXP0018", 0 }, 161 { }, 162 }; 163 MODULE_DEVICE_TABLE(acpi, fsl_8250_acpi_id); 164 165 static struct platform_driver fsl8250_platform_driver = { 166 .driver = { 167 .name = "fsl-16550-uart", 168 .acpi_match_table = ACPI_PTR(fsl_8250_acpi_id), 169 }, 170 .probe = fsl8250_acpi_probe, 171 .remove = fsl8250_acpi_remove, 172 }; 173 174 module_platform_driver(fsl8250_platform_driver); 175 #endif 176