190 lines · c
1// SPDX-License-Identifier: GPL-2.02/*3 * Freescale 16550 UART "driver", Copyright (C) 2011 Paul Gortmaker.4 * Copyright 2020 NXP5 * Copyright 2020 Puresoftware Ltd.6 *7 * This isn't a full driver; it just provides an alternate IRQ8 * 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 add12 * a check for a break and insert a dummy read on the Rx for the13 * immediately following IRQ event.14 *15 * We re-use the already existing "bug handling" lsr_saved_flags16 * field to carry the "what we just did" information from the one17 * 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 26int 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 character43 * time. This is described in the MPC8313E chip errata as "General17".44 * A typical break has a duration of 0.3s, with a 115200n8 configuration45 * that (theoretically) corresponds to ~3500 interrupts in these 0.3s.46 * In practise it's less (around 500) because of hardware47 * and software latencies. The workaround recommended by the vendor is48 * to read the RX register (to clear LSR.DR and thus prevent a FIFO49 * aging interrupt). To prevent the irq from retriggering LSR must not be50 * read. (This would clear LSR.BI, hardware would reassert the BI event51 * immediately and interrupt the CPU again. The hardware clears LSR.BI52 * 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 until79 * 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}99EXPORT_SYMBOL_GPL(fsl8250_handle_irq);100 101#ifdef CONFIG_ACPI102struct fsl8250_data {103 int line;104};105 106static 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_AUTOCONF139 | UPF_FIXED_PORT | UPF_IOREMAP140 | 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 163static 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 170static const struct acpi_device_id fsl_8250_acpi_id[] = {171 { "NXP0018", 0 },172 { },173};174MODULE_DEVICE_TABLE(acpi, fsl_8250_acpi_id);175 176static 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 185module_platform_driver(fsl8250_platform_driver);186#endif187 188MODULE_LICENSE("GPL");189MODULE_DESCRIPTION("Handling of Freescale specific 8250 variants");190