1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Copyright 2017 Google Inc
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.
9 * Typically used by the BMC to "watch" host boot progress via port
10 * 0x80 writes made by the BIOS during the boot process.
13 #include <linux/bitops.h>
14 #include <linux/clk.h>
15 #include <linux/interrupt.h>
17 #include <linux/kfifo.h>
18 #include <linux/mfd/syscon.h>
19 #include <linux/miscdevice.h>
20 #include <linux/module.h>
22 #include <linux/of_device.h>
23 #include <linux/platform_device.h>
24 #include <linux/poll.h>
25 #include <linux/regmap.h>
27 #define DEVICE_NAME "aspeed-lpc-snoop"
29 #define NUM_SNOOP_CHANNELS 2
30 #define SNOOP_FIFO_SIZE 2048
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)
38 #define HICR6_STR_SNP0W BIT(0)
39 #define HICR6_STR_SNP1W BIT(1)
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
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
51 #define HICRB_ENSNP0D BIT(14)
52 #define HICRB_ENSNP1D BIT(15)
54 struct aspeed_lpc_snoop_model_data {
55 /* The ast2400 has bits 14 and 15 as reserved, whereas the ast2500
58 unsigned int has_hicrb_ensnp;
61 struct aspeed_lpc_snoop_channel {
64 struct miscdevice miscdev;
67 struct aspeed_lpc_snoop {
68 struct regmap *regmap;
71 struct aspeed_lpc_snoop_channel chan[NUM_SNOOP_CHANNELS];
74 static struct aspeed_lpc_snoop_channel *snoop_file_to_chan(struct file *file)
76 return container_of(file->private_data,
77 struct aspeed_lpc_snoop_channel,
81 static ssize_t snoop_file_read(struct file *file, char __user *buffer,
82 size_t count, loff_t *ppos)
84 struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
88 if (kfifo_is_empty(&chan->fifo)) {
89 if (file->f_flags & O_NONBLOCK)
91 ret = wait_event_interruptible(chan->wq,
92 !kfifo_is_empty(&chan->fifo));
93 if (ret == -ERESTARTSYS)
96 ret = kfifo_to_user(&chan->fifo, buffer, count, &copied);
103 static __poll_t snoop_file_poll(struct file *file,
104 struct poll_table_struct *pt)
106 struct aspeed_lpc_snoop_channel *chan = snoop_file_to_chan(file);
108 poll_wait(file, &chan->wq, pt);
109 return !kfifo_is_empty(&chan->fifo) ? EPOLLIN : 0;
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,
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)
122 if (!kfifo_initialized(&chan->fifo))
124 if (kfifo_is_full(&chan->fifo))
125 kfifo_skip(&chan->fifo);
126 kfifo_put(&chan->fifo, val);
127 wake_up_interruptible(&chan->wq);
130 static irqreturn_t aspeed_lpc_snoop_irq(int irq, void *arg)
132 struct aspeed_lpc_snoop *lpc_snoop = arg;
135 if (regmap_read(lpc_snoop->regmap, HICR6, ®))
138 /* Check if one of the snoop channels is interrupting */
139 reg &= (HICR6_STR_SNP0W | HICR6_STR_SNP1W);
143 /* Ack pending IRQs */
144 regmap_write(lpc_snoop->regmap, HICR6, reg);
146 /* Read and save most recent snoop'ed data byte to FIFO */
147 regmap_read(lpc_snoop->regmap, SNPWDR, &data);
149 if (reg & HICR6_STR_SNP0W) {
150 u8 val = (data & SNPWDR_CH0_MASK) >> SNPWDR_CH0_SHIFT;
152 put_fifo_with_discard(&lpc_snoop->chan[0], val);
154 if (reg & HICR6_STR_SNP1W) {
155 u8 val = (data & SNPWDR_CH1_MASK) >> SNPWDR_CH1_SHIFT;
157 put_fifo_with_discard(&lpc_snoop->chan[1], val);
163 static int aspeed_lpc_snoop_config_irq(struct aspeed_lpc_snoop *lpc_snoop,
164 struct platform_device *pdev)
166 struct device *dev = &pdev->dev;
169 lpc_snoop->irq = platform_get_irq(pdev, 0);
173 rc = devm_request_irq(dev, lpc_snoop->irq,
174 aspeed_lpc_snoop_irq, IRQF_SHARED,
175 DEVICE_NAME, lpc_snoop);
177 dev_warn(dev, "Unable to request IRQ %d\n", lpc_snoop->irq);
185 static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
187 int channel, u16 lpc_port)
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);
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);
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);
210 /* Enable LPC snoop channel at requested port */
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;
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;
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,
238 static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
243 regmap_update_bits(lpc_snoop->regmap, HICR5,
244 HICR5_EN_SNP0W | HICR5_ENINT_SNP0W,
248 regmap_update_bits(lpc_snoop->regmap, HICR5,
249 HICR5_EN_SNP1W | HICR5_ENINT_SNP1W,
256 kfifo_free(&lpc_snoop->chan[channel].fifo);
257 misc_deregister(&lpc_snoop->chan[channel].miscdev);
260 static int aspeed_lpc_snoop_probe(struct platform_device *pdev)
262 struct aspeed_lpc_snoop *lpc_snoop;
264 struct device_node *np;
270 lpc_snoop = devm_kzalloc(dev, sizeof(*lpc_snoop), GFP_KERNEL);
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");
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");
288 dev_set_drvdata(&pdev->dev, lpc_snoop);
290 rc = of_property_read_u32_index(dev->of_node, "snoop-ports", 0, &port);
292 dev_err(dev, "no snoop ports configured\n");
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");
303 rc = clk_prepare_enable(lpc_snoop->clk);
305 dev_err(dev, "couldn't enable clock\n");
309 rc = aspeed_lpc_snoop_config_irq(lpc_snoop, pdev);
313 rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 0, port);
317 /* Configuration of 2nd snoop channel port is optional */
318 if (of_property_read_u32_index(dev->of_node, "snoop-ports",
320 rc = aspeed_lpc_enable_snoop(lpc_snoop, dev, 1, port);
322 aspeed_lpc_disable_snoop(lpc_snoop, 0);
330 clk_disable_unprepare(lpc_snoop->clk);
335 static int aspeed_lpc_snoop_remove(struct platform_device *pdev)
337 struct aspeed_lpc_snoop *lpc_snoop = dev_get_drvdata(&pdev->dev);
339 /* Disable both snoop channels */
340 aspeed_lpc_disable_snoop(lpc_snoop, 0);
341 aspeed_lpc_disable_snoop(lpc_snoop, 1);
343 clk_disable_unprepare(lpc_snoop->clk);
348 static const struct aspeed_lpc_snoop_model_data ast2400_model_data = {
349 .has_hicrb_ensnp = 0,
352 static const struct aspeed_lpc_snoop_model_data ast2500_model_data = {
353 .has_hicrb_ensnp = 1,
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 },
366 static struct platform_driver aspeed_lpc_snoop_driver = {
369 .of_match_table = aspeed_lpc_snoop_match,
371 .probe = aspeed_lpc_snoop_probe,
372 .remove = aspeed_lpc_snoop_remove,
375 module_platform_driver(aspeed_lpc_snoop_driver);
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");