1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
4  *
5  * Authors:
6  *   Serge Semin <Sergey.Semin@baikalelectronics.ru>
7  *
8  * Baikal-T1 APB-bus driver
9  */
10 
11 #include <linux/kernel.h>
12 #include <linux/module.h>
13 #include <linux/types.h>
14 #include <linux/device.h>
15 #include <linux/atomic.h>
16 #include <linux/platform_device.h>
17 #include <linux/interrupt.h>
18 #include <linux/io.h>
19 #include <linux/nmi.h>
20 #include <linux/of.h>
21 #include <linux/regmap.h>
22 #include <linux/clk.h>
23 #include <linux/reset.h>
24 #include <linux/time64.h>
25 #include <linux/clk.h>
26 #include <linux/sysfs.h>
27 
28 #define APB_EHB_ISR			0x00
29 #define APB_EHB_ISR_PENDING		BIT(0)
30 #define APB_EHB_ISR_MASK		BIT(1)
31 #define APB_EHB_ADDR			0x04
32 #define APB_EHB_TIMEOUT			0x08
33 
34 #define APB_EHB_TIMEOUT_MIN		0x000003FFU
35 #define APB_EHB_TIMEOUT_MAX		0xFFFFFFFFU
36 
37 /*
38  * struct bt1_apb - Baikal-T1 APB EHB private data
39  * @dev: Pointer to the device structure.
40  * @regs: APB EHB registers map.
41  * @res: No-device error injection memory region.
42  * @irq: Errors IRQ number.
43  * @rate: APB-bus reference clock rate.
44  * @pclk: APB-reference clock.
45  * @prst: APB domain reset line.
46  * @count: Number of errors detected.
47  */
48 struct bt1_apb {
49 	struct device *dev;
50 
51 	struct regmap *regs;
52 	void __iomem *res;
53 	int irq;
54 
55 	unsigned long rate;
56 	struct clk *pclk;
57 
58 	struct reset_control *prst;
59 
60 	atomic_t count;
61 };
62 
63 static const struct regmap_config bt1_apb_regmap_cfg = {
64 	.reg_bits = 32,
65 	.val_bits = 32,
66 	.reg_stride = 4,
67 	.max_register = APB_EHB_TIMEOUT,
68 	.fast_io = true
69 };
70 
bt1_apb_n_to_timeout_us(struct bt1_apb * apb,u32 n)71 static inline unsigned long bt1_apb_n_to_timeout_us(struct bt1_apb *apb, u32 n)
72 {
73 	u64 timeout = (u64)n * USEC_PER_SEC;
74 
75 	do_div(timeout, apb->rate);
76 
77 	return timeout;
78 
79 }
80 
bt1_apb_timeout_to_n_us(struct bt1_apb * apb,unsigned long timeout)81 static inline unsigned long bt1_apb_timeout_to_n_us(struct bt1_apb *apb,
82 						    unsigned long timeout)
83 {
84 	u64 n = (u64)timeout * apb->rate;
85 
86 	do_div(n, USEC_PER_SEC);
87 
88 	return n;
89 
90 }
91 
bt1_apb_isr(int irq,void * data)92 static irqreturn_t bt1_apb_isr(int irq, void *data)
93 {
94 	struct bt1_apb *apb = data;
95 	u32 addr = 0;
96 
97 	regmap_read(apb->regs, APB_EHB_ADDR, &addr);
98 
99 	dev_crit_ratelimited(apb->dev,
100 		"APB-bus fault %d: Slave access timeout at 0x%08x\n",
101 		atomic_inc_return(&apb->count),
102 		addr);
103 
104 	/*
105 	 * Print backtrace on each CPU. This might be pointless if the fault
106 	 * has happened on the same CPU as the IRQ handler is executed or
107 	 * the other core proceeded further execution despite the error.
108 	 * But if it's not, by looking at the trace we would get straight to
109 	 * the cause of the problem.
110 	 */
111 	trigger_all_cpu_backtrace();
112 
113 	regmap_update_bits(apb->regs, APB_EHB_ISR, APB_EHB_ISR_PENDING, 0);
114 
115 	return IRQ_HANDLED;
116 }
117 
bt1_apb_clear_data(void * data)118 static void bt1_apb_clear_data(void *data)
119 {
120 	struct bt1_apb *apb = data;
121 	struct platform_device *pdev = to_platform_device(apb->dev);
122 
123 	platform_set_drvdata(pdev, NULL);
124 }
125 
bt1_apb_create_data(struct platform_device * pdev)126 static struct bt1_apb *bt1_apb_create_data(struct platform_device *pdev)
127 {
128 	struct device *dev = &pdev->dev;
129 	struct bt1_apb *apb;
130 	int ret;
131 
132 	apb = devm_kzalloc(dev, sizeof(*apb), GFP_KERNEL);
133 	if (!apb)
134 		return ERR_PTR(-ENOMEM);
135 
136 	ret = devm_add_action(dev, bt1_apb_clear_data, apb);
137 	if (ret) {
138 		dev_err(dev, "Can't add APB EHB data clear action\n");
139 		return ERR_PTR(ret);
140 	}
141 
142 	apb->dev = dev;
143 	atomic_set(&apb->count, 0);
144 	platform_set_drvdata(pdev, apb);
145 
146 	return apb;
147 }
148 
bt1_apb_request_regs(struct bt1_apb * apb)149 static int bt1_apb_request_regs(struct bt1_apb *apb)
150 {
151 	struct platform_device *pdev = to_platform_device(apb->dev);
152 	void __iomem *regs;
153 
154 	regs = devm_platform_ioremap_resource_byname(pdev, "ehb");
155 	if (IS_ERR(regs)) {
156 		dev_err(apb->dev, "Couldn't map APB EHB registers\n");
157 		return PTR_ERR(regs);
158 	}
159 
160 	apb->regs = devm_regmap_init_mmio(apb->dev, regs, &bt1_apb_regmap_cfg);
161 	if (IS_ERR(apb->regs)) {
162 		dev_err(apb->dev, "Couldn't create APB EHB regmap\n");
163 		return PTR_ERR(apb->regs);
164 	}
165 
166 	apb->res = devm_platform_ioremap_resource_byname(pdev, "nodev");
167 	if (IS_ERR(apb->res))
168 		dev_err(apb->dev, "Couldn't map reserved region\n");
169 
170 	return PTR_ERR_OR_ZERO(apb->res);
171 }
172 
bt1_apb_request_rst(struct bt1_apb * apb)173 static int bt1_apb_request_rst(struct bt1_apb *apb)
174 {
175 	int ret;
176 
177 	apb->prst = devm_reset_control_get_optional_exclusive(apb->dev, "prst");
178 	if (IS_ERR(apb->prst)) {
179 		dev_warn(apb->dev, "Couldn't get reset control line\n");
180 		return PTR_ERR(apb->prst);
181 	}
182 
183 	ret = reset_control_deassert(apb->prst);
184 	if (ret)
185 		dev_err(apb->dev, "Failed to deassert the reset line\n");
186 
187 	return ret;
188 }
189 
bt1_apb_disable_clk(void * data)190 static void bt1_apb_disable_clk(void *data)
191 {
192 	struct bt1_apb *apb = data;
193 
194 	clk_disable_unprepare(apb->pclk);
195 }
196 
bt1_apb_request_clk(struct bt1_apb * apb)197 static int bt1_apb_request_clk(struct bt1_apb *apb)
198 {
199 	int ret;
200 
201 	apb->pclk = devm_clk_get(apb->dev, "pclk");
202 	if (IS_ERR(apb->pclk)) {
203 		dev_err(apb->dev, "Couldn't get APB clock descriptor\n");
204 		return PTR_ERR(apb->pclk);
205 	}
206 
207 	ret = clk_prepare_enable(apb->pclk);
208 	if (ret) {
209 		dev_err(apb->dev, "Couldn't enable the APB clock\n");
210 		return ret;
211 	}
212 
213 	ret = devm_add_action_or_reset(apb->dev, bt1_apb_disable_clk, apb);
214 	if (ret) {
215 		dev_err(apb->dev, "Can't add APB EHB clocks disable action\n");
216 		return ret;
217 	}
218 
219 	apb->rate = clk_get_rate(apb->pclk);
220 	if (!apb->rate) {
221 		dev_err(apb->dev, "Invalid clock rate\n");
222 		return -EINVAL;
223 	}
224 
225 	return 0;
226 }
227 
bt1_apb_clear_irq(void * data)228 static void bt1_apb_clear_irq(void *data)
229 {
230 	struct bt1_apb *apb = data;
231 
232 	regmap_update_bits(apb->regs, APB_EHB_ISR, APB_EHB_ISR_MASK, 0);
233 }
234 
bt1_apb_request_irq(struct bt1_apb * apb)235 static int bt1_apb_request_irq(struct bt1_apb *apb)
236 {
237 	struct platform_device *pdev = to_platform_device(apb->dev);
238 	int ret;
239 
240 	apb->irq = platform_get_irq(pdev, 0);
241 	if (apb->irq < 0)
242 		return apb->irq;
243 
244 	ret = devm_request_irq(apb->dev, apb->irq, bt1_apb_isr, IRQF_SHARED,
245 			       "bt1-apb", apb);
246 	if (ret) {
247 		dev_err(apb->dev, "Couldn't request APB EHB IRQ\n");
248 		return ret;
249 	}
250 
251 	ret = devm_add_action(apb->dev, bt1_apb_clear_irq, apb);
252 	if (ret) {
253 		dev_err(apb->dev, "Can't add APB EHB IRQs clear action\n");
254 		return ret;
255 	}
256 
257 	/* Unmask IRQ and clear it' pending flag. */
258 	regmap_update_bits(apb->regs, APB_EHB_ISR,
259 			   APB_EHB_ISR_PENDING | APB_EHB_ISR_MASK,
260 			   APB_EHB_ISR_MASK);
261 
262 	return 0;
263 }
264 
count_show(struct device * dev,struct device_attribute * attr,char * buf)265 static ssize_t count_show(struct device *dev, struct device_attribute *attr,
266 			  char *buf)
267 {
268 	struct bt1_apb *apb = dev_get_drvdata(dev);
269 
270 	return scnprintf(buf, PAGE_SIZE, "%d\n", atomic_read(&apb->count));
271 }
272 static DEVICE_ATTR_RO(count);
273 
timeout_show(struct device * dev,struct device_attribute * attr,char * buf)274 static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,
275 			    char *buf)
276 {
277 	struct bt1_apb *apb = dev_get_drvdata(dev);
278 	unsigned long timeout;
279 	int ret;
280 	u32 n;
281 
282 	ret = regmap_read(apb->regs, APB_EHB_TIMEOUT, &n);
283 	if (ret)
284 		return ret;
285 
286 	timeout = bt1_apb_n_to_timeout_us(apb, n);
287 
288 	return scnprintf(buf, PAGE_SIZE, "%lu\n", timeout);
289 }
290 
timeout_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)291 static ssize_t timeout_store(struct device *dev,
292 			     struct device_attribute *attr,
293 			     const char *buf, size_t count)
294 {
295 	struct bt1_apb *apb = dev_get_drvdata(dev);
296 	unsigned long timeout;
297 	int ret;
298 	u32 n;
299 
300 	if (kstrtoul(buf, 0, &timeout) < 0)
301 		return -EINVAL;
302 
303 	n = bt1_apb_timeout_to_n_us(apb, timeout);
304 	n = clamp(n, APB_EHB_TIMEOUT_MIN, APB_EHB_TIMEOUT_MAX);
305 
306 	ret = regmap_write(apb->regs, APB_EHB_TIMEOUT, n);
307 
308 	return ret ?: count;
309 }
310 static DEVICE_ATTR_RW(timeout);
311 
inject_error_show(struct device * dev,struct device_attribute * attr,char * buf)312 static ssize_t inject_error_show(struct device *dev,
313 				 struct device_attribute *attr, char *buf)
314 {
315 	return scnprintf(buf, PAGE_SIZE, "Error injection: nodev irq\n");
316 }
317 
inject_error_store(struct device * dev,struct device_attribute * attr,const char * data,size_t count)318 static ssize_t inject_error_store(struct device *dev,
319 				  struct device_attribute *attr,
320 				  const char *data, size_t count)
321 {
322 	struct bt1_apb *apb = dev_get_drvdata(dev);
323 
324 	/*
325 	 * Either dummy read from the unmapped address in the APB IO area
326 	 * or manually set the IRQ status.
327 	 */
328 	if (sysfs_streq(data, "nodev"))
329 		readl(apb->res);
330 	else if (sysfs_streq(data, "irq"))
331 		regmap_update_bits(apb->regs, APB_EHB_ISR, APB_EHB_ISR_PENDING,
332 				   APB_EHB_ISR_PENDING);
333 	else
334 		return -EINVAL;
335 
336 	return count;
337 }
338 static DEVICE_ATTR_RW(inject_error);
339 
340 static struct attribute *bt1_apb_sysfs_attrs[] = {
341 	&dev_attr_count.attr,
342 	&dev_attr_timeout.attr,
343 	&dev_attr_inject_error.attr,
344 	NULL
345 };
346 ATTRIBUTE_GROUPS(bt1_apb_sysfs);
347 
bt1_apb_remove_sysfs(void * data)348 static void bt1_apb_remove_sysfs(void *data)
349 {
350 	struct bt1_apb *apb = data;
351 
352 	device_remove_groups(apb->dev, bt1_apb_sysfs_groups);
353 }
354 
bt1_apb_init_sysfs(struct bt1_apb * apb)355 static int bt1_apb_init_sysfs(struct bt1_apb *apb)
356 {
357 	int ret;
358 
359 	ret = device_add_groups(apb->dev, bt1_apb_sysfs_groups);
360 	if (ret) {
361 		dev_err(apb->dev, "Failed to create EHB APB sysfs nodes\n");
362 		return ret;
363 	}
364 
365 	ret = devm_add_action_or_reset(apb->dev, bt1_apb_remove_sysfs, apb);
366 	if (ret)
367 		dev_err(apb->dev, "Can't add APB EHB sysfs remove action\n");
368 
369 	return ret;
370 }
371 
bt1_apb_probe(struct platform_device * pdev)372 static int bt1_apb_probe(struct platform_device *pdev)
373 {
374 	struct bt1_apb *apb;
375 	int ret;
376 
377 	apb = bt1_apb_create_data(pdev);
378 	if (IS_ERR(apb))
379 		return PTR_ERR(apb);
380 
381 	ret = bt1_apb_request_regs(apb);
382 	if (ret)
383 		return ret;
384 
385 	ret = bt1_apb_request_rst(apb);
386 	if (ret)
387 		return ret;
388 
389 	ret = bt1_apb_request_clk(apb);
390 	if (ret)
391 		return ret;
392 
393 	ret = bt1_apb_request_irq(apb);
394 	if (ret)
395 		return ret;
396 
397 	ret = bt1_apb_init_sysfs(apb);
398 	if (ret)
399 		return ret;
400 
401 	return 0;
402 }
403 
404 static const struct of_device_id bt1_apb_of_match[] = {
405 	{ .compatible = "baikal,bt1-apb" },
406 	{ }
407 };
408 MODULE_DEVICE_TABLE(of, bt1_apb_of_match);
409 
410 static struct platform_driver bt1_apb_driver = {
411 	.probe = bt1_apb_probe,
412 	.driver = {
413 		.name = "bt1-apb",
414 		.of_match_table = bt1_apb_of_match
415 	}
416 };
417 module_platform_driver(bt1_apb_driver);
418 
419 MODULE_AUTHOR("Serge Semin <Sergey.Semin@baikalelectronics.ru>");
420 MODULE_DESCRIPTION("Baikal-T1 APB-bus driver");
421 MODULE_LICENSE("GPL v2");
422