1 /*
2  * Copyright 2017 Google Inc
3  *
4  * This program is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU General Public License
6  * as published by the Free Software Foundation; either version
7  * 2 of the License, or (at your option) any later version.
8  *
9  * Provides a simple driver to control the ASPEED LPC snoop interface which
10  * allows the BMC to listen on and save the data written by
11  * the host to an arbitrary LPC I/O port.
12  *
13  * Typically used by the BMC to "watch" host boot progress via port
14  * 0x80 writes made by the BIOS during the boot process.
15  */
16 
17 #include <linux/bitops.h>
18 #include <linux/interrupt.h>
19 #include <linux/fs.h>
20 #include <linux/kfifo.h>
21 #include <linux/mfd/syscon.h>
22 #include <linux/miscdevice.h>
23 #include <linux/module.h>
24 #include <linux/of.h>
25 #include <linux/of_device.h>
26 #include <linux/platform_device.h>
27 #include <linux/poll.h>
28 #include <linux/regmap.h>
29 
30 #define DEVICE_NAME	"aspeed-lpc-snoop"
31 
32 #define NUM_SNOOP_CHANNELS 2
33 #define SNOOP_FIFO_SIZE 2048
34 
35 #define HICR5	0x0
36 #define HICR5_EN_SNP0W		BIT(0)
37 #define HICR5_ENINT_SNP0W	BIT(1)
38 #define HICR5_EN_SNP1W		BIT(2)
39 #define HICR5_ENINT_SNP1W	BIT(3)
40 
41 #define HICR6	0x4
42 #define HICR6_STR_SNP0W		BIT(0)
43 #define HICR6_STR_SNP1W		BIT(1)
44 #define SNPWADR	0x10
45 #define SNPWADR_CH0_MASK	GENMASK(15, 0)
46 #define SNPWADR_CH0_SHIFT	0
47 #define SNPWADR_CH1_MASK	GENMASK(31, 16)
48 #define SNPWADR_CH1_SHIFT	16
49 #define SNPWDR	0x14
50 #define SNPWDR_CH0_MASK		GENMASK(7, 0)
51 #define SNPWDR_CH0_SHIFT	0
52 #define SNPWDR_CH1_MASK		GENMASK(15, 8)
53 #define SNPWDR_CH1_SHIFT	8
54 #define HICRB	0x80
55 #define HICRB_ENSNP0D		BIT(14)
56 #define HICRB_ENSNP1D		BIT(15)
57 
58 struct aspeed_lpc_snoop_model_data {
59 	/* The ast2400 has bits 14 and 15 as reserved, whereas the ast2500
60 	 * can use them.
61 	 */
62 	unsigned int has_hicrb_ensnp;
63 };
64 
65 struct aspeed_lpc_snoop_channel {
66 	struct kfifo		fifo;
67 	wait_queue_head_t	wq;
68 	struct miscdevice	miscdev;
69 };
70 
71 struct aspeed_lpc_snoop {
72 	struct regmap		*regmap;
73 	int			irq;
74 	struct aspeed_lpc_snoop_channel chan[NUM_SNOOP_CHANNELS];
75 };
76 
77 static struct aspeed_lpc_snoop_channel *snoop_file_to_chan(struct file *file)
78 {
79 	return container_of(file->private_data,
80 			    struct aspeed_lpc_snoop_channel,
81 			    miscdev);
82 }
83 
84 static ssize_t snoop_file_read(struct file *file, char __user *buffer,
85 				size_t count, loff_t *ppos)
86 {
87 	struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
88 	unsigned int copied;
89 	int ret = 0;
90 
91 	if (kfifo_is_empty(&chan->fifo)) {
92 		if (file->f_flags & O_NONBLOCK)
93 			return -EAGAIN;
94 		ret = wait_event_interruptible(chan->wq,
95 				!kfifo_is_empty(&chan->fifo));
96 		if (ret == -ERESTARTSYS)
97 			return -EINTR;
98 	}
99 	ret = kfifo_to_user(&chan->fifo, buffer, count, &copied);
100 
101 	return ret ? ret : copied;
102 }
103 
104 static unsigned int snoop_file_poll(struct file *file,
105 				    struct poll_table_struct *pt)
106 {
107 	struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
108 
109 	poll_wait(file, &chan->wq, pt);
110 	return !kfifo_is_empty(&chan->fifo) ? POLLIN : 0;
111 }
112 
113 static const struct file_operations snoop_fops = {
114 	.owner  = THIS_MODULE,
115 	.read   = snoop_file_read,
116 	.poll   = snoop_file_poll,
117 	.llseek = noop_llseek,
118 };
119 
120 /* Save a byte to a FIFO and discard the oldest byte if FIFO is full */
121 static void put_fifo_with_discard(struct aspeed_lpc_snoop_channel *chan, u8 val)
122 {
123 	if (!kfifo_initialized(&chan->fifo))
124 		return;
125 	if (kfifo_is_full(&chan->fifo))
126 		kfifo_skip(&chan->fifo);
127 	kfifo_put(&chan->fifo, val);
128 	wake_up_interruptible(&chan->wq);
129 }
130 
131 static irqreturn_t aspeed_lpc_snoop_irq(int irq, void *arg)
132 {
133 	struct aspeed_lpc_snoop *lpc_snoop = arg;
134 	u32 reg, data;
135 
136 	if (regmap_read(lpc_snoop->regmap, HICR6, &reg))
137 		return IRQ_NONE;
138 
139 	/* Check if one of the snoop channels is interrupting */
140 	reg &= (HICR6_STR_SNP0W | HICR6_STR_SNP1W);
141 	if (!reg)
142 		return IRQ_NONE;
143 
144 	/* Ack pending IRQs */
145 	regmap_write(lpc_snoop->regmap, HICR6, reg);
146 
147 	/* Read and save most recent snoop'ed data byte to FIFO */
148 	regmap_read(lpc_snoop->regmap, SNPWDR, &data);
149 
150 	if (reg & HICR6_STR_SNP0W) {
151 		u8 val = (data & SNPWDR_CH0_MASK) >> SNPWDR_CH0_SHIFT;
152 
153 		put_fifo_with_discard(&lpc_snoop->chan[0], val);
154 	}
155 	if (reg & HICR6_STR_SNP1W) {
156 		u8 val = (data & SNPWDR_CH1_MASK) >> SNPWDR_CH1_SHIFT;
157 
158 		put_fifo_with_discard(&lpc_snoop->chan[1], val);
159 	}
160 
161 	return IRQ_HANDLED;
162 }
163 
164 static int aspeed_lpc_snoop_config_irq(struct aspeed_lpc_snoop *lpc_snoop,
165 				       struct platform_device *pdev)
166 {
167 	struct device *dev = &pdev->dev;
168 	int rc;
169 
170 	lpc_snoop->irq = platform_get_irq(pdev, 0);
171 	if (!lpc_snoop->irq)
172 		return -ENODEV;
173 
174 	rc = devm_request_irq(dev, lpc_snoop->irq,
175 			      aspeed_lpc_snoop_irq, IRQF_SHARED,
176 			      DEVICE_NAME, lpc_snoop);
177 	if (rc < 0) {
178 		dev_warn(dev, "Unable to request IRQ %d\n", lpc_snoop->irq);
179 		lpc_snoop->irq = 0;
180 		return rc;
181 	}
182 
183 	return 0;
184 }
185 
186 static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
187 				   struct device *dev,
188 				   int channel, u16 lpc_port)
189 {
190 	int rc = 0;
191 	u32 hicr5_en, snpwadr_mask, snpwadr_shift, hicrb_en;
192 	const struct aspeed_lpc_snoop_model_data *model_data =
193 		of_device_get_match_data(dev);
194 
195 	init_waitqueue_head(&lpc_snoop->chan[channel].wq);
196 	/* Create FIFO datastructure */
197 	rc = kfifo_alloc(&lpc_snoop->chan[channel].fifo,
198 			 SNOOP_FIFO_SIZE, GFP_KERNEL);
199 	if (rc)
200 		return rc;
201 
202 	lpc_snoop->chan[channel].miscdev.minor = MISC_DYNAMIC_MINOR;
203 	lpc_snoop->chan[channel].miscdev.name =
204 		devm_kasprintf(dev, GFP_KERNEL, "%s%d", DEVICE_NAME, channel);
205 	lpc_snoop->chan[channel].miscdev.fops = &snoop_fops;
206 	lpc_snoop->chan[channel].miscdev.parent = dev;
207 	rc = misc_register(&lpc_snoop->chan[channel].miscdev);
208 	if (rc)
209 		return rc;
210 
211 	/* Enable LPC snoop channel at requested port */
212 	switch (channel) {
213 	case 0:
214 		hicr5_en = HICR5_EN_SNP0W | HICR5_ENINT_SNP0W;
215 		snpwadr_mask = SNPWADR_CH0_MASK;
216 		snpwadr_shift = SNPWADR_CH0_SHIFT;
217 		hicrb_en = HICRB_ENSNP0D;
218 		break;
219 	case 1:
220 		hicr5_en = HICR5_EN_SNP1W | HICR5_ENINT_SNP1W;
221 		snpwadr_mask = SNPWADR_CH1_MASK;
222 		snpwadr_shift = SNPWADR_CH1_SHIFT;
223 		hicrb_en = HICRB_ENSNP1D;
224 		break;
225 	default:
226 		return -EINVAL;
227 	}
228 
229 	regmap_update_bits(lpc_snoop->regmap, HICR5, hicr5_en, hicr5_en);
230 	regmap_update_bits(lpc_snoop->regmap, SNPWADR, snpwadr_mask,
231 			   lpc_port << snpwadr_shift);
232 	if (model_data->has_hicrb_ensnp)
233 		regmap_update_bits(lpc_snoop->regmap, HICRB,
234 				hicrb_en, hicrb_en);
235 
236 	return rc;
237 }
238 
239 static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
240 				     int channel)
241 {
242 	switch (channel) {
243 	case 0:
244 		regmap_update_bits(lpc_snoop->regmap, HICR5,
245 				   HICR5_EN_SNP0W | HICR5_ENINT_SNP0W,
246 				   0);
247 		break;
248 	case 1:
249 		regmap_update_bits(lpc_snoop->regmap, HICR5,
250 				   HICR5_EN_SNP1W | HICR5_ENINT_SNP1W,
251 				   0);
252 		break;
253 	default:
254 		return;
255 	}
256 
257 	kfifo_free(&lpc_snoop->chan[channel].fifo);
258 	misc_deregister(&lpc_snoop->chan[channel].miscdev);
259 }
260 
261 static int aspeed_lpc_snoop_probe(struct platform_device *pdev)
262 {
263 	struct aspeed_lpc_snoop *lpc_snoop;
264 	struct device *dev;
265 	u32 port;
266 	int rc;
267 
268 	dev = &pdev->dev;
269 
270 	lpc_snoop = devm_kzalloc(dev, sizeof(*lpc_snoop), GFP_KERNEL);
271 	if (!lpc_snoop)
272 		return -ENOMEM;
273 
274 	lpc_snoop->regmap = syscon_node_to_regmap(
275 			pdev->dev.parent->of_node);
276 	if (IS_ERR(lpc_snoop->regmap)) {
277 		dev_err(dev, "Couldn't get regmap\n");
278 		return -ENODEV;
279 	}
280 
281 	dev_set_drvdata(&pdev->dev, lpc_snoop);
282 
283 	rc = of_property_read_u32_index(dev->of_node, "snoop-ports", 0, &port);
284 	if (rc) {
285 		dev_err(dev, "no snoop ports configured\n");
286 		return -ENODEV;
287 	}
288 
289 	rc = aspeed_lpc_snoop_config_irq(lpc_snoop, pdev);
290 	if (rc)
291 		return rc;
292 
293 	rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 0, port);
294 	if (rc)
295 		return rc;
296 
297 	/* Configuration of 2nd snoop channel port is optional */
298 	if (of_property_read_u32_index(dev->of_node, "snoop-ports",
299 				       1, &port) == 0) {
300 		rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 1, port);
301 		if (rc)
302 			aspeed_lpc_disable_snoop(lpc_snoop, 0);
303 	}
304 
305 	return rc;
306 }
307 
308 static int aspeed_lpc_snoop_remove(struct platform_device *pdev)
309 {
310 	struct aspeed_lpc_snoop *lpc_snoop = dev_get_drvdata(&pdev->dev);
311 
312 	/* Disable both snoop channels */
313 	aspeed_lpc_disable_snoop(lpc_snoop, 0);
314 	aspeed_lpc_disable_snoop(lpc_snoop, 1);
315 
316 	return 0;
317 }
318 
319 static const struct aspeed_lpc_snoop_model_data ast2400_model_data = {
320 	.has_hicrb_ensnp = 0,
321 };
322 
323 static const struct aspeed_lpc_snoop_model_data ast2500_model_data = {
324 	.has_hicrb_ensnp = 1,
325 };
326 
327 static const struct of_device_id aspeed_lpc_snoop_match[] = {
328 	{ .compatible = "aspeed,ast2400-lpc-snoop",
329 	  .data = &ast2400_model_data },
330 	{ .compatible = "aspeed,ast2500-lpc-snoop",
331 	  .data = &ast2500_model_data },
332 	{ },
333 };
334 
335 static struct platform_driver aspeed_lpc_snoop_driver = {
336 	.driver = {
337 		.name		= DEVICE_NAME,
338 		.of_match_table = aspeed_lpc_snoop_match,
339 	},
340 	.probe = aspeed_lpc_snoop_probe,
341 	.remove = aspeed_lpc_snoop_remove,
342 };
343 
344 module_platform_driver(aspeed_lpc_snoop_driver);
345 
346 MODULE_DEVICE_TABLE(of, aspeed_lpc_snoop_match);
347 MODULE_LICENSE("GPL");
348 MODULE_AUTHOR("Robert Lippert <rlippert@google.com>");
349 MODULE_DESCRIPTION("Linux driver to control Aspeed LPC snoop functionality");
350