1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright 2017 Google Inc
4  *
5  * Provides a simple driver to control the ASPEED LPC snoop interface which
6  * allows the BMC to listen on and save the data written by
7  * the host to an arbitrary LPC I/O port.
8  *
9  * Typically used by the BMC to "watch" host boot progress via port
10  * 0x80 writes made by the BIOS during the boot process.
11  */
12 
13 #include <linux/bitops.h>
14 #include <linux/clk.h>
15 #include <linux/interrupt.h>
16 #include <linux/fs.h>
17 #include <linux/kfifo.h>
18 #include <linux/mfd/syscon.h>
19 #include <linux/miscdevice.h>
20 #include <linux/module.h>
21 #include <linux/of.h>
22 #include <linux/of_device.h>
23 #include <linux/platform_device.h>
24 #include <linux/poll.h>
25 #include <linux/regmap.h>
26 
27 #define DEVICE_NAME	"aspeed-lpc-snoop"
28 
29 #define NUM_SNOOP_CHANNELS 2
30 #define SNOOP_FIFO_SIZE 2048
31 
32 #define HICR5	0x80
33 #define HICR5_EN_SNP0W		BIT(0)
34 #define HICR5_ENINT_SNP0W	BIT(1)
35 #define HICR5_EN_SNP1W		BIT(2)
36 #define HICR5_ENINT_SNP1W	BIT(3)
37 #define HICR6	0x84
38 #define HICR6_STR_SNP0W		BIT(0)
39 #define HICR6_STR_SNP1W		BIT(1)
40 #define SNPWADR	0x90
41 #define SNPWADR_CH0_MASK	GENMASK(15, 0)
42 #define SNPWADR_CH0_SHIFT	0
43 #define SNPWADR_CH1_MASK	GENMASK(31, 16)
44 #define SNPWADR_CH1_SHIFT	16
45 #define SNPWDR	0x94
46 #define SNPWDR_CH0_MASK		GENMASK(7, 0)
47 #define SNPWDR_CH0_SHIFT	0
48 #define SNPWDR_CH1_MASK		GENMASK(15, 8)
49 #define SNPWDR_CH1_SHIFT	8
50 #define HICRB	0x100
51 #define HICRB_ENSNP0D		BIT(14)
52 #define HICRB_ENSNP1D		BIT(15)
53 
54 struct aspeed_lpc_snoop_model_data {
55 	/* The ast2400 has bits 14 and 15 as reserved, whereas the ast2500
56 	 * can use them.
57 	 */
58 	unsigned int has_hicrb_ensnp;
59 };
60 
61 struct aspeed_lpc_snoop_channel {
62 	struct kfifo		fifo;
63 	wait_queue_head_t	wq;
64 	struct miscdevice	miscdev;
65 };
66 
67 struct aspeed_lpc_snoop {
68 	struct regmap		*regmap;
69 	int			irq;
70 	struct clk		*clk;
71 	struct aspeed_lpc_snoop_channel chan[NUM_SNOOP_CHANNELS];
72 };
73 
74 static struct aspeed_lpc_snoop_channel *snoop_file_to_chan(struct file *file)
75 {
76 	return container_of(file->private_data,
77 			    struct aspeed_lpc_snoop_channel,
78 			    miscdev);
79 }
80 
81 static ssize_t snoop_file_read(struct file *file, char __user *buffer,
82 				size_t count, loff_t *ppos)
83 {
84 	struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
85 	unsigned int copied;
86 	int ret = 0;
87 
88 	if (kfifo_is_empty(&chan->fifo)) {
89 		if (file->f_flags & O_NONBLOCK)
90 			return -EAGAIN;
91 		ret = wait_event_interruptible(chan->wq,
92 				!kfifo_is_empty(&chan->fifo));
93 		if (ret == -ERESTARTSYS)
94 			return -EINTR;
95 	}
96 	ret = kfifo_to_user(&chan->fifo, buffer, count, &copied);
97 	if (ret)
98 		return ret;
99 
100 	return copied;
101 }
102 
103 static __poll_t snoop_file_poll(struct file *file,
104 				    struct poll_table_struct *pt)
105 {
106 	struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
107 
108 	poll_wait(file, &chan->wq, pt);
109 	return !kfifo_is_empty(&chan->fifo) ? EPOLLIN : 0;
110 }
111 
112 static const struct file_operations snoop_fops = {
113 	.owner  = THIS_MODULE,
114 	.read   = snoop_file_read,
115 	.poll   = snoop_file_poll,
116 	.llseek = noop_llseek,
117 };
118 
119 /* Save a byte to a FIFO and discard the oldest byte if FIFO is full */
120 static void put_fifo_with_discard(struct aspeed_lpc_snoop_channel *chan, u8 val)
121 {
122 	if (!kfifo_initialized(&chan->fifo))
123 		return;
124 	if (kfifo_is_full(&chan->fifo))
125 		kfifo_skip(&chan->fifo);
126 	kfifo_put(&chan->fifo, val);
127 	wake_up_interruptible(&chan->wq);
128 }
129 
130 static irqreturn_t aspeed_lpc_snoop_irq(int irq, void *arg)
131 {
132 	struct aspeed_lpc_snoop *lpc_snoop = arg;
133 	u32 reg, data;
134 
135 	if (regmap_read(lpc_snoop->regmap, HICR6, &reg))
136 		return IRQ_NONE;
137 
138 	/* Check if one of the snoop channels is interrupting */
139 	reg &= (HICR6_STR_SNP0W | HICR6_STR_SNP1W);
140 	if (!reg)
141 		return IRQ_NONE;
142 
143 	/* Ack pending IRQs */
144 	regmap_write(lpc_snoop->regmap, HICR6, reg);
145 
146 	/* Read and save most recent snoop'ed data byte to FIFO */
147 	regmap_read(lpc_snoop->regmap, SNPWDR, &data);
148 
149 	if (reg & HICR6_STR_SNP0W) {
150 		u8 val = (data & SNPWDR_CH0_MASK) >> SNPWDR_CH0_SHIFT;
151 
152 		put_fifo_with_discard(&lpc_snoop->chan[0], val);
153 	}
154 	if (reg & HICR6_STR_SNP1W) {
155 		u8 val = (data & SNPWDR_CH1_MASK) >> SNPWDR_CH1_SHIFT;
156 
157 		put_fifo_with_discard(&lpc_snoop->chan[1], val);
158 	}
159 
160 	return IRQ_HANDLED;
161 }
162 
163 static int aspeed_lpc_snoop_config_irq(struct aspeed_lpc_snoop *lpc_snoop,
164 				       struct platform_device *pdev)
165 {
166 	struct device *dev = &pdev->dev;
167 	int rc;
168 
169 	lpc_snoop->irq = platform_get_irq(pdev, 0);
170 	if (!lpc_snoop->irq)
171 		return -ENODEV;
172 
173 	rc = devm_request_irq(dev, lpc_snoop->irq,
174 			      aspeed_lpc_snoop_irq, IRQF_SHARED,
175 			      DEVICE_NAME, lpc_snoop);
176 	if (rc < 0) {
177 		dev_warn(dev, "Unable to request IRQ %d\n", lpc_snoop->irq);
178 		lpc_snoop->irq = 0;
179 		return rc;
180 	}
181 
182 	return 0;
183 }
184 
185 static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
186 				   struct device *dev,
187 				   int channel, u16 lpc_port)
188 {
189 	int rc = 0;
190 	u32 hicr5_en, snpwadr_mask, snpwadr_shift, hicrb_en;
191 	const struct aspeed_lpc_snoop_model_data *model_data =
192 		of_device_get_match_data(dev);
193 
194 	init_waitqueue_head(&lpc_snoop->chan[channel].wq);
195 	/* Create FIFO datastructure */
196 	rc = kfifo_alloc(&lpc_snoop->chan[channel].fifo,
197 			 SNOOP_FIFO_SIZE, GFP_KERNEL);
198 	if (rc)
199 		return rc;
200 
201 	lpc_snoop->chan[channel].miscdev.minor = MISC_DYNAMIC_MINOR;
202 	lpc_snoop->chan[channel].miscdev.name =
203 		devm_kasprintf(dev, GFP_KERNEL, "%s%d", DEVICE_NAME, channel);
204 	lpc_snoop->chan[channel].miscdev.fops = &snoop_fops;
205 	lpc_snoop->chan[channel].miscdev.parent = dev;
206 	rc = misc_register(&lpc_snoop->chan[channel].miscdev);
207 	if (rc)
208 		return rc;
209 
210 	/* Enable LPC snoop channel at requested port */
211 	switch (channel) {
212 	case 0:
213 		hicr5_en = HICR5_EN_SNP0W | HICR5_ENINT_SNP0W;
214 		snpwadr_mask = SNPWADR_CH0_MASK;
215 		snpwadr_shift = SNPWADR_CH0_SHIFT;
216 		hicrb_en = HICRB_ENSNP0D;
217 		break;
218 	case 1:
219 		hicr5_en = HICR5_EN_SNP1W | HICR5_ENINT_SNP1W;
220 		snpwadr_mask = SNPWADR_CH1_MASK;
221 		snpwadr_shift = SNPWADR_CH1_SHIFT;
222 		hicrb_en = HICRB_ENSNP1D;
223 		break;
224 	default:
225 		return -EINVAL;
226 	}
227 
228 	regmap_update_bits(lpc_snoop->regmap, HICR5, hicr5_en, hicr5_en);
229 	regmap_update_bits(lpc_snoop->regmap, SNPWADR, snpwadr_mask,
230 			   lpc_port << snpwadr_shift);
231 	if (model_data->has_hicrb_ensnp)
232 		regmap_update_bits(lpc_snoop->regmap, HICRB,
233 				hicrb_en, hicrb_en);
234 
235 	return rc;
236 }
237 
238 static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
239 				     int channel)
240 {
241 	switch (channel) {
242 	case 0:
243 		regmap_update_bits(lpc_snoop->regmap, HICR5,
244 				   HICR5_EN_SNP0W | HICR5_ENINT_SNP0W,
245 				   0);
246 		break;
247 	case 1:
248 		regmap_update_bits(lpc_snoop->regmap, HICR5,
249 				   HICR5_EN_SNP1W | HICR5_ENINT_SNP1W,
250 				   0);
251 		break;
252 	default:
253 		return;
254 	}
255 
256 	kfifo_free(&lpc_snoop->chan[channel].fifo);
257 	misc_deregister(&lpc_snoop->chan[channel].miscdev);
258 }
259 
260 static int aspeed_lpc_snoop_probe(struct platform_device *pdev)
261 {
262 	struct aspeed_lpc_snoop *lpc_snoop;
263 	struct device *dev;
264 	struct device_node *np;
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 	np = pdev->dev.parent->of_node;
275 	if (!of_device_is_compatible(np, "aspeed,ast2400-lpc-v2") &&
276 	    !of_device_is_compatible(np, "aspeed,ast2500-lpc-v2") &&
277 	    !of_device_is_compatible(np, "aspeed,ast2600-lpc-v2")) {
278 		dev_err(dev, "unsupported LPC device binding\n");
279 		return -ENODEV;
280 	}
281 
282 	lpc_snoop->regmap = syscon_node_to_regmap(np);
283 	if (IS_ERR(lpc_snoop->regmap)) {
284 		dev_err(dev, "Couldn't get regmap\n");
285 		return -ENODEV;
286 	}
287 
288 	dev_set_drvdata(&pdev->dev, lpc_snoop);
289 
290 	rc = of_property_read_u32_index(dev->of_node, "snoop-ports", 0, &port);
291 	if (rc) {
292 		dev_err(dev, "no snoop ports configured\n");
293 		return -ENODEV;
294 	}
295 
296 	lpc_snoop->clk = devm_clk_get(dev, NULL);
297 	if (IS_ERR(lpc_snoop->clk)) {
298 		rc = PTR_ERR(lpc_snoop->clk);
299 		if (rc != -EPROBE_DEFER)
300 			dev_err(dev, "couldn't get clock\n");
301 		return rc;
302 	}
303 	rc = clk_prepare_enable(lpc_snoop->clk);
304 	if (rc) {
305 		dev_err(dev, "couldn't enable clock\n");
306 		return rc;
307 	}
308 
309 	rc = aspeed_lpc_snoop_config_irq(lpc_snoop, pdev);
310 	if (rc)
311 		goto err;
312 
313 	rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 0, port);
314 	if (rc)
315 		goto err;
316 
317 	/* Configuration of 2nd snoop channel port is optional */
318 	if (of_property_read_u32_index(dev->of_node, "snoop-ports",
319 				       1, &port) == 0) {
320 		rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 1, port);
321 		if (rc) {
322 			aspeed_lpc_disable_snoop(lpc_snoop, 0);
323 			goto err;
324 		}
325 	}
326 
327 	return 0;
328 
329 err:
330 	clk_disable_unprepare(lpc_snoop->clk);
331 
332 	return rc;
333 }
334 
335 static int aspeed_lpc_snoop_remove(struct platform_device *pdev)
336 {
337 	struct aspeed_lpc_snoop *lpc_snoop = dev_get_drvdata(&pdev->dev);
338 
339 	/* Disable both snoop channels */
340 	aspeed_lpc_disable_snoop(lpc_snoop, 0);
341 	aspeed_lpc_disable_snoop(lpc_snoop, 1);
342 
343 	clk_disable_unprepare(lpc_snoop->clk);
344 
345 	return 0;
346 }
347 
348 static const struct aspeed_lpc_snoop_model_data ast2400_model_data = {
349 	.has_hicrb_ensnp = 0,
350 };
351 
352 static const struct aspeed_lpc_snoop_model_data ast2500_model_data = {
353 	.has_hicrb_ensnp = 1,
354 };
355 
356 static const struct of_device_id aspeed_lpc_snoop_match[] = {
357 	{ .compatible = "aspeed,ast2400-lpc-snoop",
358 	  .data = &ast2400_model_data },
359 	{ .compatible = "aspeed,ast2500-lpc-snoop",
360 	  .data = &ast2500_model_data },
361 	{ .compatible = "aspeed,ast2600-lpc-snoop",
362 	  .data = &ast2500_model_data },
363 	{ },
364 };
365 
366 static struct platform_driver aspeed_lpc_snoop_driver = {
367 	.driver = {
368 		.name		= DEVICE_NAME,
369 		.of_match_table = aspeed_lpc_snoop_match,
370 	},
371 	.probe = aspeed_lpc_snoop_probe,
372 	.remove = aspeed_lpc_snoop_remove,
373 };
374 
375 module_platform_driver(aspeed_lpc_snoop_driver);
376 
377 MODULE_DEVICE_TABLE(of, aspeed_lpc_snoop_match);
378 MODULE_LICENSE("GPL");
379 MODULE_AUTHOR("Robert Lippert <rlippert@google.com>");
380 MODULE_DESCRIPTION("Linux driver to control Aspeed LPC snoop functionality");
381