1 // SPDX-License-Identifier: GPL-2.0
3 * Freescale 16550 UART "driver", Copyright (C) 2011 Paul Gortmaker.
5 * Copyright 2020 Puresoftware Ltd.
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.
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.
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.
20 #include <linux/acpi.h>
21 #include <linux/serial_reg.h>
22 #include <linux/serial_8250.h>
30 int fsl8250_handle_irq(struct uart_port *port)
32 unsigned char lsr, orig_lsr;
35 struct uart_8250_port *up = up_to_u8250p(port);
37 spin_lock_irqsave(&up->port.lock, flags);
39 iir = port->serial_in(port, UART_IIR);
40 if (iir & UART_IIR_NO_INT) {
41 spin_unlock_irqrestore(&up->port.lock, flags);
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);
53 lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR);
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);
61 /* Stop processing interrupts on input overrun */
62 if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) {
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);
69 /* Keep restarting the timer until
70 * the input overrun subsides.
72 cancel_delayed_work(&up->overrun_backoff);
75 delay = msecs_to_jiffies(up->overrun_backoff_time_ms);
76 schedule_delayed_work(&up->overrun_backoff, delay);
79 serial8250_modem_status(up);
81 if ((lsr & UART_LSR_THRE) && (up->ier & UART_IER_THRI))
82 serial8250_tx_chars(up);
84 up->lsr_saved_flags = orig_lsr;
85 uart_unlock_and_check_sysrq(&up->port, flags);
88 EXPORT_SYMBOL_GPL(fsl8250_handle_irq);
91 static int fsl8250_acpi_probe(struct platform_device *pdev)
93 struct fsl8250_data *data;
94 struct uart_8250_port port8250;
95 struct device *dev = &pdev->dev;
96 struct resource *regs;
100 regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
102 dev_err(dev, "no registers defined\n");
106 irq = platform_get_irq(pdev, 0);
108 if (irq != -EPROBE_DEFER)
109 dev_err(dev, "cannot get irq\n");
113 memset(&port8250, 0, sizeof(port8250));
115 ret = device_property_read_u32(dev, "clock-frequency",
116 &port8250.port.uartclk);
120 spin_lock_init(&port8250.port.lock);
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
129 port8250.port.dev = dev;
130 port8250.port.mapsize = resource_size(regs);
131 port8250.port.iotype = UPIO_MEM;
132 port8250.port.irqflags = IRQF_SHARED;
134 port8250.port.membase = devm_ioremap(dev, port8250.port.mapbase,
135 port8250.port.mapsize);
136 if (!port8250.port.membase)
139 data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
143 data->line = serial8250_register_8250_port(&port8250);
147 platform_set_drvdata(pdev, data);
151 static int fsl8250_acpi_remove(struct platform_device *pdev)
153 struct fsl8250_data *data = platform_get_drvdata(pdev);
155 serial8250_unregister_port(data->line);
159 static const struct acpi_device_id fsl_8250_acpi_id[] = {
163 MODULE_DEVICE_TABLE(acpi, fsl_8250_acpi_id);
165 static struct platform_driver fsl8250_platform_driver = {
167 .name = "fsl-16550-uart",
168 .acpi_match_table = ACPI_PTR(fsl_8250_acpi_id),
170 .probe = fsl8250_acpi_probe,
171 .remove = fsl8250_acpi_remove,
174 module_platform_driver(fsl8250_platform_driver);