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	0x0
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
38#define HICR6	0x4
39#define HICR6_STR_SNP0W		BIT(0)
40#define HICR6_STR_SNP1W		BIT(1)
41#define SNPWADR	0x10
42#define SNPWADR_CH0_MASK	GENMASK(15, 0)
43#define SNPWADR_CH0_SHIFT	0
44#define SNPWADR_CH1_MASK	GENMASK(31, 16)
45#define SNPWADR_CH1_SHIFT	16
46#define SNPWDR	0x14
47#define SNPWDR_CH0_MASK		GENMASK(7, 0)
48#define SNPWDR_CH0_SHIFT	0
49#define SNPWDR_CH1_MASK		GENMASK(15, 8)
50#define SNPWDR_CH1_SHIFT	8
51#define HICRB	0x80
52#define HICRB_ENSNP0D		BIT(14)
53#define HICRB_ENSNP1D		BIT(15)
54
55struct aspeed_lpc_snoop_model_data {
56	/* The ast2400 has bits 14 and 15 as reserved, whereas the ast2500
57	 * can use them.
58	 */
59	unsigned int has_hicrb_ensnp;
60};
61
62struct aspeed_lpc_snoop_channel {
63	struct kfifo		fifo;
64	wait_queue_head_t	wq;
65	struct miscdevice	miscdev;
66};
67
68struct aspeed_lpc_snoop {
69	struct regmap		*regmap;
70	int			irq;
71	struct clk		*clk;
72	struct aspeed_lpc_snoop_channel chan[NUM_SNOOP_CHANNELS];
73};
74
75static struct aspeed_lpc_snoop_channel *snoop_file_to_chan(struct file *file)
76{
77	return container_of(file->private_data,
78			    struct aspeed_lpc_snoop_channel,
79			    miscdev);
80}
81
82static ssize_t snoop_file_read(struct file *file, char __user *buffer,
83				size_t count, loff_t *ppos)
84{
85	struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
86	unsigned int copied;
87	int ret = 0;
88
89	if (kfifo_is_empty(&chan->fifo)) {
90		if (file->f_flags & O_NONBLOCK)
91			return -EAGAIN;
92		ret = wait_event_interruptible(chan->wq,
93				!kfifo_is_empty(&chan->fifo));
94		if (ret == -ERESTARTSYS)
95			return -EINTR;
96	}
97	ret = kfifo_to_user(&chan->fifo, buffer, count, &copied);
98	if (ret)
99		return ret;
100
101	return copied;
102}
103
104static __poll_t 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) ? EPOLLIN : 0;
111}
112
113static 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 */
121static 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
131static 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
164static 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
186static 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
239static 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
261static 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	lpc_snoop->clk = devm_clk_get(dev, NULL);
290	if (IS_ERR(lpc_snoop->clk)) {
291		rc = PTR_ERR(lpc_snoop->clk);
292		if (rc != -EPROBE_DEFER)
293			dev_err(dev, "couldn't get clock\n");
294		return rc;
295	}
296	rc = clk_prepare_enable(lpc_snoop->clk);
297	if (rc) {
298		dev_err(dev, "couldn't enable clock\n");
299		return rc;
300	}
301
302	rc = aspeed_lpc_snoop_config_irq(lpc_snoop, pdev);
303	if (rc)
304		goto err;
305
306	rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 0, port);
307	if (rc)
308		goto err;
309
310	/* Configuration of 2nd snoop channel port is optional */
311	if (of_property_read_u32_index(dev->of_node, "snoop-ports",
312				       1, &port) == 0) {
313		rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 1, port);
314		if (rc) {
315			aspeed_lpc_disable_snoop(lpc_snoop, 0);
316			goto err;
317		}
318	}
319
320	return 0;
321
322err:
323	clk_disable_unprepare(lpc_snoop->clk);
324
325	return rc;
326}
327
328static int aspeed_lpc_snoop_remove(struct platform_device *pdev)
329{
330	struct aspeed_lpc_snoop *lpc_snoop = dev_get_drvdata(&pdev->dev);
331
332	/* Disable both snoop channels */
333	aspeed_lpc_disable_snoop(lpc_snoop, 0);
334	aspeed_lpc_disable_snoop(lpc_snoop, 1);
335
336	clk_disable_unprepare(lpc_snoop->clk);
337
338	return 0;
339}
340
341static const struct aspeed_lpc_snoop_model_data ast2400_model_data = {
342	.has_hicrb_ensnp = 0,
343};
344
345static const struct aspeed_lpc_snoop_model_data ast2500_model_data = {
346	.has_hicrb_ensnp = 1,
347};
348
349static const struct of_device_id aspeed_lpc_snoop_match[] = {
350	{ .compatible = "aspeed,ast2400-lpc-snoop",
351	  .data = &ast2400_model_data },
352	{ .compatible = "aspeed,ast2500-lpc-snoop",
353	  .data = &ast2500_model_data },
354	{ },
355};
356
357static struct platform_driver aspeed_lpc_snoop_driver = {
358	.driver = {
359		.name		= DEVICE_NAME,
360		.of_match_table = aspeed_lpc_snoop_match,
361	},
362	.probe = aspeed_lpc_snoop_probe,
363	.remove = aspeed_lpc_snoop_remove,
364};
365
366module_platform_driver(aspeed_lpc_snoop_driver);
367
368MODULE_DEVICE_TABLE(of, aspeed_lpc_snoop_match);
369MODULE_LICENSE("GPL");
370MODULE_AUTHOR("Robert Lippert <rlippert@google.com>");
371MODULE_DESCRIPTION("Linux driver to control Aspeed LPC snoop functionality");
372