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/dev_printk.h>
16 #include <linux/interrupt.h>
17 #include <linux/fs.h>
18 #include <linux/kfifo.h>
19 #include <linux/mfd/syscon.h>
20 #include <linux/miscdevice.h>
21 #include <linux/module.h>
22 #include <linux/of.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 SNOOP_FIFO_SIZE 2048
30
31 #define HICR5 0x80
32 #define HICR5_EN_SNP0W BIT(0)
33 #define HICR5_ENINT_SNP0W BIT(1)
34 #define HICR5_EN_SNP1W BIT(2)
35 #define HICR5_ENINT_SNP1W BIT(3)
36 #define HICR6 0x84
37 #define HICR6_STR_SNP0W BIT(0)
38 #define HICR6_STR_SNP1W BIT(1)
39 #define SNPWADR 0x90
40 #define SNPWADR_CH0_MASK GENMASK(15, 0)
41 #define SNPWADR_CH0_SHIFT 0
42 #define SNPWADR_CH1_MASK GENMASK(31, 16)
43 #define SNPWADR_CH1_SHIFT 16
44 #define SNPWDR 0x94
45 #define SNPWDR_CH0_MASK GENMASK(7, 0)
46 #define SNPWDR_CH0_SHIFT 0
47 #define SNPWDR_CH1_MASK GENMASK(15, 8)
48 #define SNPWDR_CH1_SHIFT 8
49 #define HICRB 0x100
50 #define HICRB_ENSNP0D BIT(14)
51 #define HICRB_ENSNP1D BIT(15)
52
53 struct aspeed_lpc_snoop_model_data {
54 /* The ast2400 has bits 14 and 15 as reserved, whereas the ast2500
55 * can use them.
56 */
57 unsigned int has_hicrb_ensnp;
58 };
59
60 enum aspeed_lpc_snoop_index {
61 ASPEED_LPC_SNOOP_INDEX_0 = 0,
62 ASPEED_LPC_SNOOP_INDEX_1 = 1,
63 ASPEED_LPC_SNOOP_INDEX_MAX = ASPEED_LPC_SNOOP_INDEX_1,
64 };
65
66 struct aspeed_lpc_snoop_channel_cfg {
67 enum aspeed_lpc_snoop_index index;
68 u32 hicr5_en;
69 u32 snpwadr_mask;
70 u32 snpwadr_shift;
71 u32 hicrb_en;
72 };
73
74 struct aspeed_lpc_snoop_channel {
75 const struct aspeed_lpc_snoop_channel_cfg *cfg;
76 bool enabled;
77 struct kfifo fifo;
78 wait_queue_head_t wq;
79 struct miscdevice miscdev;
80 };
81
82 struct aspeed_lpc_snoop {
83 struct regmap *regmap;
84 int irq;
85 struct clk *clk;
86 struct aspeed_lpc_snoop_channel chan[ASPEED_LPC_SNOOP_INDEX_MAX + 1];
87 };
88
89 static const struct aspeed_lpc_snoop_channel_cfg channel_cfgs[ASPEED_LPC_SNOOP_INDEX_MAX + 1] = {
90 {
91 .index = ASPEED_LPC_SNOOP_INDEX_0,
92 .hicr5_en = HICR5_EN_SNP0W | HICR5_ENINT_SNP0W,
93 .snpwadr_mask = SNPWADR_CH0_MASK,
94 .snpwadr_shift = SNPWADR_CH0_SHIFT,
95 .hicrb_en = HICRB_ENSNP0D,
96 },
97 {
98 .index = ASPEED_LPC_SNOOP_INDEX_1,
99 .hicr5_en = HICR5_EN_SNP1W | HICR5_ENINT_SNP1W,
100 .snpwadr_mask = SNPWADR_CH1_MASK,
101 .snpwadr_shift = SNPWADR_CH1_SHIFT,
102 .hicrb_en = HICRB_ENSNP1D,
103 },
104 };
105
snoop_file_to_chan(struct file * file)106 static struct aspeed_lpc_snoop_channel *snoop_file_to_chan(struct file *file)
107 {
108 return container_of(file->private_data,
109 struct aspeed_lpc_snoop_channel,
110 miscdev);
111 }
112
snoop_file_read(struct file * file,char __user * buffer,size_t count,loff_t * ppos)113 static ssize_t snoop_file_read(struct file *file, char __user *buffer,
114 size_t count, loff_t *ppos)
115 {
116 struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
117 unsigned int copied;
118 int ret = 0;
119
120 if (kfifo_is_empty(&chan->fifo)) {
121 if (file->f_flags & O_NONBLOCK)
122 return -EAGAIN;
123 ret = wait_event_interruptible(chan->wq,
124 !kfifo_is_empty(&chan->fifo));
125 if (ret == -ERESTARTSYS)
126 return -EINTR;
127 }
128 ret = kfifo_to_user(&chan->fifo, buffer, count, &copied);
129 if (ret)
130 return ret;
131
132 return copied;
133 }
134
snoop_file_poll(struct file * file,struct poll_table_struct * pt)135 static __poll_t snoop_file_poll(struct file *file,
136 struct poll_table_struct *pt)
137 {
138 struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
139
140 poll_wait(file, &chan->wq, pt);
141 return !kfifo_is_empty(&chan->fifo) ? EPOLLIN : 0;
142 }
143
144 static const struct file_operations snoop_fops = {
145 .owner = THIS_MODULE,
146 .read = snoop_file_read,
147 .poll = snoop_file_poll,
148 .llseek = noop_llseek,
149 };
150
151 /* 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)152 static void put_fifo_with_discard(struct aspeed_lpc_snoop_channel *chan, u8 val)
153 {
154 if (!kfifo_initialized(&chan->fifo))
155 return;
156 if (kfifo_is_full(&chan->fifo))
157 kfifo_skip(&chan->fifo);
158 kfifo_put(&chan->fifo, val);
159 wake_up_interruptible(&chan->wq);
160 }
161
aspeed_lpc_snoop_irq(int irq,void * arg)162 static irqreturn_t aspeed_lpc_snoop_irq(int irq, void *arg)
163 {
164 struct aspeed_lpc_snoop *lpc_snoop = arg;
165 u32 reg, data;
166
167 if (regmap_read(lpc_snoop->regmap, HICR6, ®))
168 return IRQ_NONE;
169
170 /* Check if one of the snoop channels is interrupting */
171 reg &= (HICR6_STR_SNP0W | HICR6_STR_SNP1W);
172 if (!reg)
173 return IRQ_NONE;
174
175 /* Ack pending IRQs */
176 regmap_write(lpc_snoop->regmap, HICR6, reg);
177
178 /* Read and save most recent snoop'ed data byte to FIFO */
179 regmap_read(lpc_snoop->regmap, SNPWDR, &data);
180
181 if (reg & HICR6_STR_SNP0W) {
182 u8 val = (data & SNPWDR_CH0_MASK) >> SNPWDR_CH0_SHIFT;
183
184 put_fifo_with_discard(&lpc_snoop->chan[0], val);
185 }
186 if (reg & HICR6_STR_SNP1W) {
187 u8 val = (data & SNPWDR_CH1_MASK) >> SNPWDR_CH1_SHIFT;
188
189 put_fifo_with_discard(&lpc_snoop->chan[1], val);
190 }
191
192 return IRQ_HANDLED;
193 }
194
aspeed_lpc_snoop_config_irq(struct aspeed_lpc_snoop * lpc_snoop,struct platform_device * pdev)195 static int aspeed_lpc_snoop_config_irq(struct aspeed_lpc_snoop *lpc_snoop,
196 struct platform_device *pdev)
197 {
198 struct device *dev = &pdev->dev;
199 int rc;
200
201 lpc_snoop->irq = platform_get_irq(pdev, 0);
202 if (lpc_snoop->irq < 0)
203 return -ENODEV;
204
205 rc = devm_request_irq(dev, lpc_snoop->irq,
206 aspeed_lpc_snoop_irq, IRQF_SHARED,
207 DEVICE_NAME, lpc_snoop);
208 if (rc < 0) {
209 dev_warn(dev, "Unable to request IRQ %d\n", lpc_snoop->irq);
210 lpc_snoop->irq = 0;
211 return rc;
212 }
213
214 return 0;
215 }
216
217 __attribute__((nonnull))
aspeed_lpc_enable_snoop(struct device * dev,struct aspeed_lpc_snoop * lpc_snoop,struct aspeed_lpc_snoop_channel * channel,const struct aspeed_lpc_snoop_channel_cfg * cfg,u16 lpc_port)218 static int aspeed_lpc_enable_snoop(struct device *dev,
219 struct aspeed_lpc_snoop *lpc_snoop,
220 struct aspeed_lpc_snoop_channel *channel,
221 const struct aspeed_lpc_snoop_channel_cfg *cfg,
222 u16 lpc_port)
223 {
224 const struct aspeed_lpc_snoop_model_data *model_data;
225 int rc = 0;
226
227 if (WARN_ON(channel->enabled))
228 return -EBUSY;
229
230 init_waitqueue_head(&channel->wq);
231
232 channel->cfg = cfg;
233 channel->miscdev.minor = MISC_DYNAMIC_MINOR;
234 channel->miscdev.fops = &snoop_fops;
235 channel->miscdev.parent = dev;
236
237 channel->miscdev.name =
238 devm_kasprintf(dev, GFP_KERNEL, "%s%d", DEVICE_NAME, cfg->index);
239 if (!channel->miscdev.name)
240 return -ENOMEM;
241
242 rc = kfifo_alloc(&channel->fifo, SNOOP_FIFO_SIZE, GFP_KERNEL);
243 if (rc)
244 return rc;
245
246 rc = misc_register(&channel->miscdev);
247 if (rc)
248 goto err_free_fifo;
249
250 /* Enable LPC snoop channel at requested port */
251 regmap_set_bits(lpc_snoop->regmap, HICR5, cfg->hicr5_en);
252 regmap_update_bits(lpc_snoop->regmap, SNPWADR, cfg->snpwadr_mask,
253 lpc_port << cfg->snpwadr_shift);
254
255 model_data = of_device_get_match_data(dev);
256 if (model_data && model_data->has_hicrb_ensnp)
257 regmap_set_bits(lpc_snoop->regmap, HICRB, cfg->hicrb_en);
258
259 channel->enabled = true;
260
261 return 0;
262
263 err_free_fifo:
264 kfifo_free(&channel->fifo);
265 return rc;
266 }
267
268 __attribute__((nonnull))
aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop * lpc_snoop,struct aspeed_lpc_snoop_channel * channel)269 static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
270 struct aspeed_lpc_snoop_channel *channel)
271 {
272 if (!channel->enabled)
273 return;
274
275 /* Disable interrupts along with the device */
276 regmap_clear_bits(lpc_snoop->regmap, HICR5, channel->cfg->hicr5_en);
277
278 channel->enabled = false;
279 /* Consider improving safety wrt concurrent reader(s) */
280 misc_deregister(&channel->miscdev);
281 kfifo_free(&channel->fifo);
282 }
283
aspeed_lpc_snoop_remove(struct platform_device * pdev)284 static void aspeed_lpc_snoop_remove(struct platform_device *pdev)
285 {
286 struct aspeed_lpc_snoop *lpc_snoop = dev_get_drvdata(&pdev->dev);
287
288 /* Disable both snoop channels */
289 aspeed_lpc_disable_snoop(lpc_snoop, &lpc_snoop->chan[0]);
290 aspeed_lpc_disable_snoop(lpc_snoop, &lpc_snoop->chan[1]);
291 }
292
aspeed_lpc_snoop_probe(struct platform_device * pdev)293 static int aspeed_lpc_snoop_probe(struct platform_device *pdev)
294 {
295 struct aspeed_lpc_snoop *lpc_snoop;
296 struct device_node *np;
297 struct device *dev;
298 int idx;
299 int rc;
300
301 dev = &pdev->dev;
302
303 lpc_snoop = devm_kzalloc(dev, sizeof(*lpc_snoop), GFP_KERNEL);
304 if (!lpc_snoop)
305 return -ENOMEM;
306
307 np = pdev->dev.parent->of_node;
308 if (!of_device_is_compatible(np, "aspeed,ast2400-lpc-v2") &&
309 !of_device_is_compatible(np, "aspeed,ast2500-lpc-v2") &&
310 !of_device_is_compatible(np, "aspeed,ast2600-lpc-v2")) {
311 dev_err(dev, "unsupported LPC device binding\n");
312 return -ENODEV;
313 }
314
315 lpc_snoop->regmap = syscon_node_to_regmap(np);
316 if (IS_ERR(lpc_snoop->regmap))
317 return dev_err_probe(dev, PTR_ERR(lpc_snoop->regmap), "Couldn't get regmap\n");
318
319 dev_set_drvdata(&pdev->dev, lpc_snoop);
320
321 lpc_snoop->clk = devm_clk_get_enabled(dev, NULL);
322 if (IS_ERR(lpc_snoop->clk))
323 return dev_err_probe(dev, PTR_ERR(lpc_snoop->clk), "couldn't get clock");
324
325 rc = aspeed_lpc_snoop_config_irq(lpc_snoop, pdev);
326 if (rc)
327 return rc;
328
329 static_assert(ARRAY_SIZE(channel_cfgs) == ARRAY_SIZE(lpc_snoop->chan),
330 "Broken implementation assumption regarding cfg count");
331 for (idx = ASPEED_LPC_SNOOP_INDEX_0; idx <= ASPEED_LPC_SNOOP_INDEX_MAX; idx++) {
332 u32 port;
333
334 rc = of_property_read_u32_index(dev->of_node, "snoop-ports", idx, &port);
335 if (rc)
336 break;
337
338 rc = aspeed_lpc_enable_snoop(dev, lpc_snoop, &lpc_snoop->chan[idx],
339 &channel_cfgs[idx], port);
340 if (rc)
341 goto cleanup_channels;
342 }
343
344 return idx == ASPEED_LPC_SNOOP_INDEX_0 ? -ENODEV : 0;
345
346 cleanup_channels:
347 aspeed_lpc_snoop_remove(pdev);
348
349 return rc;
350 }
351
352 static const struct aspeed_lpc_snoop_model_data ast2400_model_data = {
353 .has_hicrb_ensnp = 0,
354 };
355
356 static const struct aspeed_lpc_snoop_model_data ast2500_model_data = {
357 .has_hicrb_ensnp = 1,
358 };
359
360 static const struct of_device_id aspeed_lpc_snoop_match[] = {
361 { .compatible = "aspeed,ast2400-lpc-snoop",
362 .data = &ast2400_model_data },
363 { .compatible = "aspeed,ast2500-lpc-snoop",
364 .data = &ast2500_model_data },
365 { .compatible = "aspeed,ast2600-lpc-snoop",
366 .data = &ast2500_model_data },
367 { },
368 };
369
370 static struct platform_driver aspeed_lpc_snoop_driver = {
371 .driver = {
372 .name = DEVICE_NAME,
373 .of_match_table = aspeed_lpc_snoop_match,
374 },
375 .probe = aspeed_lpc_snoop_probe,
376 .remove_new = aspeed_lpc_snoop_remove,
377 };
378
379 module_platform_driver(aspeed_lpc_snoop_driver);
380
381 MODULE_DEVICE_TABLE(of, aspeed_lpc_snoop_match);
382 MODULE_LICENSE("GPL");
383 MODULE_AUTHOR("Robert Lippert <rlippert@google.com>");
384 MODULE_DESCRIPTION("Linux driver to control Aspeed LPC snoop functionality");
385