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
26struct fsl8250_data {
27	int	line;
28};
29
30int 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}
88EXPORT_SYMBOL_GPL(fsl8250_handle_irq);
89
90#ifdef CONFIG_ACPI
91static 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
151static 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
159static const struct acpi_device_id fsl_8250_acpi_id[] = {
160	{ "NXP0018", 0 },
161	{ },
162};
163MODULE_DEVICE_TABLE(acpi, fsl_8250_acpi_id);
164
165static 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
174module_platform_driver(fsl8250_platform_driver);
175#endif
176