aspeed-lpc-snoop.c

  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
 53struct 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
 60enum 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
 66struct 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
 74struct 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
 82struct 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
 89static 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
106static 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
113static 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
135static __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
144static 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 */
152static 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
162static 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, &reg))
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
195static 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))
218static 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
263err_free_fifo:
264	kfifo_free(&channel->fifo);
265	return rc;
266}
267
268__attribute__((nonnull))
269static 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
284static 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
293static 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
346cleanup_channels:
347	aspeed_lpc_snoop_remove(pdev);
348
349	return rc;
350}
351
352static const struct aspeed_lpc_snoop_model_data ast2400_model_data = {
353	.has_hicrb_ensnp = 0,
354};
355
356static const struct aspeed_lpc_snoop_model_data ast2500_model_data = {
357	.has_hicrb_ensnp = 1,
358};
359
360static 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
370static 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 = aspeed_lpc_snoop_remove,
377};
378
379module_platform_driver(aspeed_lpc_snoop_driver);
380
381MODULE_DEVICE_TABLE(of, aspeed_lpc_snoop_match);
382MODULE_LICENSE("GPL");
383MODULE_AUTHOR("Robert Lippert <rlippert@google.com>");
384MODULE_DESCRIPTION("Linux driver to control Aspeed LPC snoop functionality");