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