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
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	spin_lock_irqsave(&up->port.lock, flags);
34
35	iir = port->serial_in(port, UART_IIR);
36	if (iir & UART_IIR_NO_INT) {
37		spin_unlock_irqrestore(&up->port.lock, 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		spin_unlock_irqrestore(&up->port.lock, 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}
98EXPORT_SYMBOL_GPL(fsl8250_handle_irq);
99
100#ifdef CONFIG_ACPI
101struct fsl8250_data {
102	int	line;
103};
104
105static 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
162static 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
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			= fsl8250_acpi_remove,
183};
184
185module_platform_driver(fsl8250_platform_driver);
186#endif
187
188MODULE_LICENSE("GPL");
189MODULE_DESCRIPTION("Handling of Freescale specific 8250 variants");
190