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