1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 *  Amstrad E3 (Delta) keyboard port driver
4 *
5 *  Copyright (c) 2006 Matt Callow
6 *  Copyright (c) 2010 Janusz Krzysztofik
7 *
8 * Thanks to Cliff Lawson for his help
9 *
10 * The Amstrad Delta keyboard (aka mailboard) uses normal PC-AT style serial
11 * transmission.  The keyboard port is formed of two GPIO lines, for clock
12 * and data.  Due to strict timing requirements of the interface,
13 * the serial data stream is read and processed by a FIQ handler.
14 * The resulting words are fetched by this driver from a circular buffer.
15 *
16 * Standard AT keyboard driver (atkbd) is used for handling the keyboard data.
17 * However, when used with the E3 mailboard that producecs non-standard
18 * scancodes, a custom key table must be prepared and loaded from userspace.
19 */
20#include <linux/irq.h>
21#include <linux/platform_data/ams-delta-fiq.h>
22#include <linux/platform_device.h>
23#include <linux/regulator/consumer.h>
24#include <linux/serio.h>
25#include <linux/slab.h>
26#include <linux/module.h>
27
28#define DRIVER_NAME	"ams-delta-serio"
29
30MODULE_AUTHOR("Matt Callow");
31MODULE_DESCRIPTION("AMS Delta (E3) keyboard port driver");
32MODULE_LICENSE("GPL");
33
34struct ams_delta_serio {
35	struct serio *serio;
36	struct regulator *vcc;
37	unsigned int *fiq_buffer;
38};
39
40static int check_data(struct serio *serio, int data)
41{
42	int i, parity = 0;
43
44	/* check valid stop bit */
45	if (!(data & 0x400)) {
46		dev_warn(&serio->dev, "invalid stop bit, data=0x%X\n", data);
47		return SERIO_FRAME;
48	}
49	/* calculate the parity */
50	for (i = 1; i < 10; i++) {
51		if (data & (1 << i))
52			parity++;
53	}
54	/* it should be odd */
55	if (!(parity & 0x01)) {
56		dev_warn(&serio->dev,
57			 "parity check failed, data=0x%X parity=0x%X\n", data,
58			 parity);
59		return SERIO_PARITY;
60	}
61	return 0;
62}
63
64static irqreturn_t ams_delta_serio_interrupt(int irq, void *dev_id)
65{
66	struct ams_delta_serio *priv = dev_id;
67	int *circ_buff = &priv->fiq_buffer[FIQ_CIRC_BUFF];
68	int data, dfl;
69	u8 scancode;
70
71	priv->fiq_buffer[FIQ_IRQ_PEND] = 0;
72
73	/*
74	 * Read data from the circular buffer, check it
75	 * and then pass it on the serio
76	 */
77	while (priv->fiq_buffer[FIQ_KEYS_CNT] > 0) {
78
79		data = circ_buff[priv->fiq_buffer[FIQ_HEAD_OFFSET]++];
80		priv->fiq_buffer[FIQ_KEYS_CNT]--;
81		if (priv->fiq_buffer[FIQ_HEAD_OFFSET] ==
82		    priv->fiq_buffer[FIQ_BUF_LEN])
83			priv->fiq_buffer[FIQ_HEAD_OFFSET] = 0;
84
85		dfl = check_data(priv->serio, data);
86		scancode = (u8) (data >> 1) & 0xFF;
87		serio_interrupt(priv->serio, scancode, dfl);
88	}
89	return IRQ_HANDLED;
90}
91
92static int ams_delta_serio_open(struct serio *serio)
93{
94	struct ams_delta_serio *priv = serio->port_data;
95
96	/* enable keyboard */
97	return regulator_enable(priv->vcc);
98}
99
100static void ams_delta_serio_close(struct serio *serio)
101{
102	struct ams_delta_serio *priv = serio->port_data;
103
104	/* disable keyboard */
105	regulator_disable(priv->vcc);
106}
107
108static int ams_delta_serio_init(struct platform_device *pdev)
109{
110	struct ams_delta_serio *priv;
111	struct serio *serio;
112	int irq, err;
113
114	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
115	if (!priv)
116		return -ENOMEM;
117
118	priv->fiq_buffer = pdev->dev.platform_data;
119	if (!priv->fiq_buffer)
120		return -EINVAL;
121
122	priv->vcc = devm_regulator_get(&pdev->dev, "vcc");
123	if (IS_ERR(priv->vcc)) {
124		err = PTR_ERR(priv->vcc);
125		dev_err(&pdev->dev, "regulator request failed (%d)\n", err);
126		/*
127		 * When running on a non-dt platform and requested regulator
128		 * is not available, devm_regulator_get() never returns
129		 * -EPROBE_DEFER as it is not able to justify if the regulator
130		 * may still appear later.  On the other hand, the board can
131		 * still set full constriants flag at late_initcall in order
132		 * to instruct devm_regulator_get() to returnn a dummy one
133		 * if sufficient.  Hence, if we get -ENODEV here, let's convert
134		 * it to -EPROBE_DEFER and wait for the board to decide or
135		 * let Deferred Probe infrastructure handle this error.
136		 */
137		if (err == -ENODEV)
138			err = -EPROBE_DEFER;
139		return err;
140	}
141
142	irq = platform_get_irq(pdev, 0);
143	if (irq < 0)
144		return -ENXIO;
145
146	err = devm_request_irq(&pdev->dev, irq, ams_delta_serio_interrupt,
147			       IRQ_TYPE_EDGE_RISING, DRIVER_NAME, priv);
148	if (err < 0) {
149		dev_err(&pdev->dev, "IRQ request failed (%d)\n", err);
150		return err;
151	}
152
153	serio = kzalloc(sizeof(*serio), GFP_KERNEL);
154	if (!serio)
155		return -ENOMEM;
156
157	priv->serio = serio;
158
159	serio->id.type = SERIO_8042;
160	serio->open = ams_delta_serio_open;
161	serio->close = ams_delta_serio_close;
162	strscpy(serio->name, "AMS DELTA keyboard adapter", sizeof(serio->name));
163	strscpy(serio->phys, dev_name(&pdev->dev), sizeof(serio->phys));
164	serio->dev.parent = &pdev->dev;
165	serio->port_data = priv;
166
167	serio_register_port(serio);
168
169	platform_set_drvdata(pdev, priv);
170
171	dev_info(&serio->dev, "%s\n", serio->name);
172
173	return 0;
174}
175
176static int ams_delta_serio_exit(struct platform_device *pdev)
177{
178	struct ams_delta_serio *priv = platform_get_drvdata(pdev);
179
180	serio_unregister_port(priv->serio);
181
182	return 0;
183}
184
185static struct platform_driver ams_delta_serio_driver = {
186	.probe	= ams_delta_serio_init,
187	.remove	= ams_delta_serio_exit,
188	.driver	= {
189		.name	= DRIVER_NAME
190	},
191};
192module_platform_driver(ams_delta_serio_driver);
193