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 struct fsl8250_data {
27 int line;
28 };
29
fsl8250_handle_irq(struct uart_port * port)30 int 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 & UART_LSR_BI;
85
86 uart_unlock_and_check_sysrq_irqrestore(&up->port, flags);
87
88 return 1;
89 }
90 EXPORT_SYMBOL_GPL(fsl8250_handle_irq);
91
92 #ifdef CONFIG_ACPI
fsl8250_acpi_probe(struct platform_device * pdev)93 static int fsl8250_acpi_probe(struct platform_device *pdev)
94 {
95 struct fsl8250_data *data;
96 struct uart_8250_port port8250;
97 struct device *dev = &pdev->dev;
98 struct resource *regs;
99
100 int ret, irq;
101
102 regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
103 if (!regs) {
104 dev_err(dev, "no registers defined\n");
105 return -EINVAL;
106 }
107
108 irq = platform_get_irq(pdev, 0);
109 if (irq < 0)
110 return irq;
111
112 memset(&port8250, 0, sizeof(port8250));
113
114 ret = device_property_read_u32(dev, "clock-frequency",
115 &port8250.port.uartclk);
116 if (ret)
117 return ret;
118
119 spin_lock_init(&port8250.port.lock);
120
121 port8250.port.mapbase = regs->start;
122 port8250.port.irq = irq;
123 port8250.port.handle_irq = fsl8250_handle_irq;
124 port8250.port.type = PORT_16550A;
125 port8250.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
126 | UPF_FIXED_PORT | UPF_IOREMAP
127 | UPF_FIXED_TYPE;
128 port8250.port.dev = dev;
129 port8250.port.mapsize = resource_size(regs);
130 port8250.port.iotype = UPIO_MEM;
131 port8250.port.irqflags = IRQF_SHARED;
132
133 port8250.port.membase = devm_ioremap(dev, port8250.port.mapbase,
134 port8250.port.mapsize);
135 if (!port8250.port.membase)
136 return -ENOMEM;
137
138 data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
139 if (!data)
140 return -ENOMEM;
141
142 data->line = serial8250_register_8250_port(&port8250);
143 if (data->line < 0)
144 return data->line;
145
146 platform_set_drvdata(pdev, data);
147 return 0;
148 }
149
fsl8250_acpi_remove(struct platform_device * pdev)150 static int fsl8250_acpi_remove(struct platform_device *pdev)
151 {
152 struct fsl8250_data *data = platform_get_drvdata(pdev);
153
154 serial8250_unregister_port(data->line);
155 return 0;
156 }
157
158 static const struct acpi_device_id fsl_8250_acpi_id[] = {
159 { "NXP0018", 0 },
160 { },
161 };
162 MODULE_DEVICE_TABLE(acpi, fsl_8250_acpi_id);
163
164 static struct platform_driver fsl8250_platform_driver = {
165 .driver = {
166 .name = "fsl-16550-uart",
167 .acpi_match_table = ACPI_PTR(fsl_8250_acpi_id),
168 },
169 .probe = fsl8250_acpi_probe,
170 .remove = fsl8250_acpi_remove,
171 };
172
173 module_platform_driver(fsl8250_platform_driver);
174 #endif
175