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 uart_port_lock_irqsave(&up->port, &flags); 34 35 iir = port->serial_in(port, UART_IIR); 36 if (iir & UART_IIR_NO_INT) { 37 uart_port_unlock_irqrestore(&up->port, flags); 38 return 0; 39 } 40 41 /* 42 * For a single break the hardware reports LSR.BI for each character 43 * time. This is described in the MPC8313E chip errata as "General17". 44 * A typical break has a duration of 0.3s, with a 115200n8 configuration 45 * that (theoretically) corresponds to ~3500 interrupts in these 0.3s. 46 * In practise it's less (around 500) because of hardware 47 * and software latencies. The workaround recommended by the vendor is 48 * to read the RX register (to clear LSR.DR and thus prevent a FIFO 49 * aging interrupt). To prevent the irq from retriggering LSR must not be 50 * read. (This would clear LSR.BI, hardware would reassert the BI event 51 * immediately and interrupt the CPU again. The hardware clears LSR.BI 52 * when the next valid char is read.) 53 */ 54 if (unlikely(up->lsr_saved_flags & UART_LSR_BI)) { 55 up->lsr_saved_flags &= ~UART_LSR_BI; 56 port->serial_in(port, UART_RX); 57 uart_port_unlock_irqrestore(&up->port, flags); 58 return 1; 59 } 60 61 lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR); 62 63 /* Process incoming characters first */ 64 if ((lsr & (UART_LSR_DR | UART_LSR_BI)) && 65 (up->ier & (UART_IER_RLSI | UART_IER_RDI))) { 66 lsr = serial8250_rx_chars(up, lsr); 67 } 68 69 /* Stop processing interrupts on input overrun */ 70 if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) { 71 unsigned long delay; 72 73 up->ier = port->serial_in(port, UART_IER); 74 if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) { 75 port->ops->stop_rx(port); 76 } else { 77 /* Keep restarting the timer until 78 * the input overrun subsides. 79 */ 80 cancel_delayed_work(&up->overrun_backoff); 81 } 82 83 delay = msecs_to_jiffies(up->overrun_backoff_time_ms); 84 schedule_delayed_work(&up->overrun_backoff, delay); 85 } 86 87 serial8250_modem_status(up); 88 89 if ((lsr & UART_LSR_THRE) && (up->ier & UART_IER_THRI)) 90 serial8250_tx_chars(up); 91 92 up->lsr_saved_flags |= orig_lsr & UART_LSR_BI; 93 94 uart_unlock_and_check_sysrq_irqrestore(&up->port, flags); 95 96 return 1; 97 } 98 EXPORT_SYMBOL_GPL(fsl8250_handle_irq); 99 100 #ifdef CONFIG_ACPI 101 struct fsl8250_data { 102 int line; 103 }; 104 105 static int fsl8250_acpi_probe(struct platform_device *pdev) 106 { 107 struct fsl8250_data *data; 108 struct uart_8250_port port8250; 109 struct device *dev = &pdev->dev; 110 struct resource *regs; 111 112 int ret, irq; 113 114 regs = platform_get_resource(pdev, IORESOURCE_MEM, 0); 115 if (!regs) { 116 dev_err(dev, "no registers defined\n"); 117 return -EINVAL; 118 } 119 120 irq = platform_get_irq(pdev, 0); 121 if (irq < 0) 122 return irq; 123 124 memset(&port8250, 0, sizeof(port8250)); 125 126 ret = device_property_read_u32(dev, "clock-frequency", 127 &port8250.port.uartclk); 128 if (ret) 129 return ret; 130 131 spin_lock_init(&port8250.port.lock); 132 133 port8250.port.mapbase = regs->start; 134 port8250.port.irq = irq; 135 port8250.port.handle_irq = fsl8250_handle_irq; 136 port8250.port.type = PORT_16550A; 137 port8250.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF 138 | UPF_FIXED_PORT | UPF_IOREMAP 139 | UPF_FIXED_TYPE; 140 port8250.port.dev = dev; 141 port8250.port.mapsize = resource_size(regs); 142 port8250.port.iotype = UPIO_MEM; 143 port8250.port.irqflags = IRQF_SHARED; 144 145 port8250.port.membase = devm_ioremap(dev, port8250.port.mapbase, 146 port8250.port.mapsize); 147 if (!port8250.port.membase) 148 return -ENOMEM; 149 150 data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL); 151 if (!data) 152 return -ENOMEM; 153 154 data->line = serial8250_register_8250_port(&port8250); 155 if (data->line < 0) 156 return data->line; 157 158 platform_set_drvdata(pdev, data); 159 return 0; 160 } 161 162 static int fsl8250_acpi_remove(struct platform_device *pdev) 163 { 164 struct fsl8250_data *data = platform_get_drvdata(pdev); 165 166 serial8250_unregister_port(data->line); 167 return 0; 168 } 169 170 static const struct acpi_device_id fsl_8250_acpi_id[] = { 171 { "NXP0018", 0 }, 172 { }, 173 }; 174 MODULE_DEVICE_TABLE(acpi, fsl_8250_acpi_id); 175 176 static struct platform_driver fsl8250_platform_driver = { 177 .driver = { 178 .name = "fsl-16550-uart", 179 .acpi_match_table = ACPI_PTR(fsl_8250_acpi_id), 180 }, 181 .probe = fsl8250_acpi_probe, 182 .remove = fsl8250_acpi_remove, 183 }; 184 185 module_platform_driver(fsl8250_platform_driver); 186 #endif 187 188 MODULE_LICENSE("GPL"); 189 MODULE_DESCRIPTION("Handling of Freescale specific 8250 variants"); 190