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
55 struct 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
62 struct aspeed_lpc_snoop_channel {
63 struct kfifo fifo;
64 wait_queue_head_t wq;
65 struct miscdevice miscdev;
66 };
67
68 struct 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
snoop_file_to_chan(struct file *file)75 static 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
snoop_file_read(struct file *file, char __user *buffer, size_t count, loff_t *ppos)82 static 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
snoop_file_poll(struct file *file, struct poll_table_struct *pt)104 static __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
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 */
put_fifo_with_discard(struct aspeed_lpc_snoop_channel *chan, u8 val)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
aspeed_lpc_snoop_irq(int irq, void *arg)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, ®))
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
aspeed_lpc_snoop_config_irq(struct aspeed_lpc_snoop *lpc_snoop, struct platform_device *pdev)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
aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop, struct device *dev, int channel, u16 lpc_port)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
aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop, int channel)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
aspeed_lpc_snoop_probe(struct platform_device *pdev)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 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
322 err:
323 clk_disable_unprepare(lpc_snoop->clk);
324
325 return rc;
326 }
327
aspeed_lpc_snoop_remove(struct platform_device *pdev)328 static 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
341 static const struct aspeed_lpc_snoop_model_data ast2400_model_data = {
342 .has_hicrb_ensnp = 0,
343 };
344
345 static const struct aspeed_lpc_snoop_model_data ast2500_model_data = {
346 .has_hicrb_ensnp = 1,
347 };
348
349 static 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
357 static 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
366 module_platform_driver(aspeed_lpc_snoop_driver);
367
368 MODULE_DEVICE_TABLE(of, aspeed_lpc_snoop_match);
369 MODULE_LICENSE("GPL");
370 MODULE_AUTHOR("Robert Lippert <rlippert@google.com>");
371 MODULE_DESCRIPTION("Linux driver to control Aspeed LPC snoop functionality");
372