1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Serial port driver for BCM2835AUX UART
4  *
5  * Copyright (C) 2016 Martin Sperl <kernel@martin.sperl.org>
6  *
7  * Based on 8250_lpc18xx.c:
8  * Copyright (C) 2015 Joachim Eastwood <manabian@gmail.com>
9  */
10 
11 #include <linux/clk.h>
12 #include <linux/io.h>
13 #include <linux/module.h>
14 #include <linux/of.h>
15 #include <linux/platform_device.h>
16 
17 #include "8250.h"
18 
19 struct bcm2835aux_data {
20 	struct uart_8250_port uart;
21 	struct clk *clk;
22 	int line;
23 };
24 
25 static int bcm2835aux_serial_probe(struct platform_device *pdev)
26 {
27 	struct bcm2835aux_data *data;
28 	struct resource *res;
29 	int ret;
30 
31 	/* allocate the custom structure */
32 	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
33 	if (!data)
34 		return -ENOMEM;
35 
36 	/* initialize data */
37 	spin_lock_init(&data->uart.port.lock);
38 	data->uart.capabilities = UART_CAP_FIFO | UART_CAP_MINI;
39 	data->uart.port.dev = &pdev->dev;
40 	data->uart.port.regshift = 2;
41 	data->uart.port.type = PORT_16550;
42 	data->uart.port.iotype = UPIO_MEM;
43 	data->uart.port.fifosize = 8;
44 	data->uart.port.flags = UPF_SHARE_IRQ |
45 				UPF_FIXED_PORT |
46 				UPF_FIXED_TYPE |
47 				UPF_SKIP_TEST;
48 
49 	/* get the clock - this also enables the HW */
50 	data->clk = devm_clk_get(&pdev->dev, NULL);
51 	ret = PTR_ERR_OR_ZERO(data->clk);
52 	if (ret) {
53 		dev_err(&pdev->dev, "could not get clk: %d\n", ret);
54 		return ret;
55 	}
56 
57 	/* get the interrupt */
58 	ret = platform_get_irq(pdev, 0);
59 	if (ret < 0) {
60 		dev_err(&pdev->dev, "irq not found - %i", ret);
61 		return ret;
62 	}
63 	data->uart.port.irq = ret;
64 
65 	/* map the main registers */
66 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
67 	if (!res) {
68 		dev_err(&pdev->dev, "memory resource not found");
69 		return -EINVAL;
70 	}
71 	data->uart.port.membase = devm_ioremap_resource(&pdev->dev, res);
72 	ret = PTR_ERR_OR_ZERO(data->uart.port.membase);
73 	if (ret)
74 		return ret;
75 
76 	/* Check for a fixed line number */
77 	ret = of_alias_get_id(pdev->dev.of_node, "serial");
78 	if (ret >= 0)
79 		data->uart.port.line = ret;
80 
81 	/* enable the clock as a last step */
82 	ret = clk_prepare_enable(data->clk);
83 	if (ret) {
84 		dev_err(&pdev->dev, "unable to enable uart clock - %d\n",
85 			ret);
86 		return ret;
87 	}
88 
89 	/* the HW-clock divider for bcm2835aux is 8,
90 	 * but 8250 expects a divider of 16,
91 	 * so we have to multiply the actual clock by 2
92 	 * to get identical baudrates.
93 	 */
94 	data->uart.port.uartclk = clk_get_rate(data->clk) * 2;
95 
96 	/* register the port */
97 	ret = serial8250_register_8250_port(&data->uart);
98 	if (ret < 0) {
99 		dev_err(&pdev->dev, "unable to register 8250 port - %d\n",
100 			ret);
101 		goto dis_clk;
102 	}
103 	data->line = ret;
104 
105 	platform_set_drvdata(pdev, data);
106 
107 	return 0;
108 
109 dis_clk:
110 	clk_disable_unprepare(data->clk);
111 	return ret;
112 }
113 
114 static int bcm2835aux_serial_remove(struct platform_device *pdev)
115 {
116 	struct bcm2835aux_data *data = platform_get_drvdata(pdev);
117 
118 	serial8250_unregister_port(data->uart.port.line);
119 	clk_disable_unprepare(data->clk);
120 
121 	return 0;
122 }
123 
124 static const struct of_device_id bcm2835aux_serial_match[] = {
125 	{ .compatible = "brcm,bcm2835-aux-uart" },
126 	{ },
127 };
128 MODULE_DEVICE_TABLE(of, bcm2835aux_serial_match);
129 
130 static struct platform_driver bcm2835aux_serial_driver = {
131 	.driver = {
132 		.name = "bcm2835-aux-uart",
133 		.of_match_table = bcm2835aux_serial_match,
134 	},
135 	.probe  = bcm2835aux_serial_probe,
136 	.remove = bcm2835aux_serial_remove,
137 };
138 module_platform_driver(bcm2835aux_serial_driver);
139 
140 MODULE_DESCRIPTION("BCM2835 auxiliar UART driver");
141 MODULE_AUTHOR("Martin Sperl <kernel@martin.sperl.org>");
142 MODULE_LICENSE("GPL v2");
143