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
fsl8250_handle_irq(struct uart_port * port)26 int 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 }
98 EXPORT_SYMBOL_GPL(fsl8250_handle_irq);
99
100 #ifdef CONFIG_ACPI
101 struct fsl8250_data {
102 int line;
103 };
104
fsl8250_acpi_probe(struct platform_device * pdev)105 static 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
fsl8250_acpi_remove(struct platform_device * pdev)162 static 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
170 static const struct acpi_device_id fsl_8250_acpi_id[] = {
171 { "NXP0018", 0 },
172 { },
173 };
174 MODULE_DEVICE_TABLE(acpi, fsl_8250_acpi_id);
175
176 static 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
185 module_platform_driver(fsl8250_platform_driver);
186 #endif
187
188 MODULE_LICENSE("GPL");
189 MODULE_DESCRIPTION("Handling of Freescale specific 8250 variants");
190
