1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2017 SiFive
4  * Copyright (C) 2018 Christoph Hellwig
5  */
6 #define pr_fmt(fmt) "plic: " fmt
7 #include <linux/cpu.h>
8 #include <linux/interrupt.h>
9 #include <linux/io.h>
10 #include <linux/irq.h>
11 #include <linux/irqchip.h>
12 #include <linux/irqchip/chained_irq.h>
13 #include <linux/irqdomain.h>
14 #include <linux/module.h>
15 #include <linux/of.h>
16 #include <linux/of_address.h>
17 #include <linux/of_irq.h>
18 #include <linux/platform_device.h>
19 #include <linux/spinlock.h>
20 #include <asm/smp.h>
21 
22 /*
23  * This driver implements a version of the RISC-V PLIC with the actual layout
24  * specified in chapter 8 of the SiFive U5 Coreplex Series Manual:
25  *
26  *     https://static.dev.sifive.com/U54-MC-RVCoreIP.pdf
27  *
28  * The largest number supported by devices marked as 'sifive,plic-1.0.0', is
29  * 1024, of which device 0 is defined as non-existent by the RISC-V Privileged
30  * Spec.
31  */
32 
33 #define MAX_DEVICES			1024
34 #define MAX_CONTEXTS			15872
35 
36 /*
37  * Each interrupt source has a priority register associated with it.
38  * We always hardwire it to one in Linux.
39  */
40 #define PRIORITY_BASE			0
41 #define     PRIORITY_PER_ID		4
42 
43 /*
44  * Each hart context has a vector of interrupt enable bits associated with it.
45  * There's one bit for each interrupt source.
46  */
47 #define ENABLE_BASE			0x2000
48 #define     ENABLE_PER_HART		0x80
49 
50 /*
51  * Each hart context has a set of control registers associated with it.  Right
52  * now there's only two: a source priority threshold over which the hart will
53  * take an interrupt, and a register to claim interrupts.
54  */
55 #define CONTEXT_BASE			0x200000
56 #define     CONTEXT_PER_HART		0x1000
57 #define     CONTEXT_THRESHOLD		0x00
58 #define     CONTEXT_CLAIM		0x04
59 
60 #define	PLIC_DISABLE_THRESHOLD		0x7
61 #define	PLIC_ENABLE_THRESHOLD		0
62 
63 struct plic_priv {
64 	struct cpumask lmask;
65 	struct irq_domain *irqdomain;
66 	void __iomem *regs;
67 };
68 
69 struct plic_handler {
70 	bool			present;
71 	void __iomem		*hart_base;
72 	/*
73 	 * Protect mask operations on the registers given that we can't
74 	 * assume atomic memory operations work on them.
75 	 */
76 	raw_spinlock_t		enable_lock;
77 	void __iomem		*enable_base;
78 	struct plic_priv	*priv;
79 };
80 static int plic_parent_irq;
81 static bool plic_cpuhp_setup_done;
82 static DEFINE_PER_CPU(struct plic_handler, plic_handlers);
83 
84 static inline void plic_toggle(struct plic_handler *handler,
85 				int hwirq, int enable)
86 {
87 	u32 __iomem *reg = handler->enable_base + (hwirq / 32) * sizeof(u32);
88 	u32 hwirq_mask = 1 << (hwirq % 32);
89 
90 	raw_spin_lock(&handler->enable_lock);
91 	if (enable)
92 		writel(readl(reg) | hwirq_mask, reg);
93 	else
94 		writel(readl(reg) & ~hwirq_mask, reg);
95 	raw_spin_unlock(&handler->enable_lock);
96 }
97 
98 static inline void plic_irq_toggle(const struct cpumask *mask,
99 				   struct irq_data *d, int enable)
100 {
101 	int cpu;
102 	struct plic_priv *priv = irq_data_get_irq_chip_data(d);
103 
104 	writel(enable, priv->regs + PRIORITY_BASE + d->hwirq * PRIORITY_PER_ID);
105 	for_each_cpu(cpu, mask) {
106 		struct plic_handler *handler = per_cpu_ptr(&plic_handlers, cpu);
107 
108 		if (handler->present &&
109 		    cpumask_test_cpu(cpu, &handler->priv->lmask))
110 			plic_toggle(handler, d->hwirq, enable);
111 	}
112 }
113 
114 static void plic_irq_unmask(struct irq_data *d)
115 {
116 	struct cpumask amask;
117 	unsigned int cpu;
118 	struct plic_priv *priv = irq_data_get_irq_chip_data(d);
119 
120 	cpumask_and(&amask, &priv->lmask, cpu_online_mask);
121 	cpu = cpumask_any_and(irq_data_get_affinity_mask(d),
122 					   &amask);
123 	if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
124 		return;
125 	plic_irq_toggle(cpumask_of(cpu), d, 1);
126 }
127 
128 static void plic_irq_mask(struct irq_data *d)
129 {
130 	struct plic_priv *priv = irq_data_get_irq_chip_data(d);
131 
132 	plic_irq_toggle(&priv->lmask, d, 0);
133 }
134 
135 #ifdef CONFIG_SMP
136 static int plic_set_affinity(struct irq_data *d,
137 			     const struct cpumask *mask_val, bool force)
138 {
139 	unsigned int cpu;
140 	struct cpumask amask;
141 	struct plic_priv *priv = irq_data_get_irq_chip_data(d);
142 
143 	cpumask_and(&amask, &priv->lmask, mask_val);
144 
145 	if (force)
146 		cpu = cpumask_first(&amask);
147 	else
148 		cpu = cpumask_any_and(&amask, cpu_online_mask);
149 
150 	if (cpu >= nr_cpu_ids)
151 		return -EINVAL;
152 
153 	plic_irq_toggle(&priv->lmask, d, 0);
154 	plic_irq_toggle(cpumask_of(cpu), d, !irqd_irq_masked(d));
155 
156 	irq_data_update_effective_affinity(d, cpumask_of(cpu));
157 
158 	return IRQ_SET_MASK_OK_DONE;
159 }
160 #endif
161 
162 static void plic_irq_eoi(struct irq_data *d)
163 {
164 	struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
165 
166 	writel(d->hwirq, handler->hart_base + CONTEXT_CLAIM);
167 }
168 
169 static struct irq_chip plic_chip = {
170 	.name		= "SiFive PLIC",
171 	.irq_mask	= plic_irq_mask,
172 	.irq_unmask	= plic_irq_unmask,
173 	.irq_eoi	= plic_irq_eoi,
174 #ifdef CONFIG_SMP
175 	.irq_set_affinity = plic_set_affinity,
176 #endif
177 };
178 
179 static int plic_irqdomain_map(struct irq_domain *d, unsigned int irq,
180 			      irq_hw_number_t hwirq)
181 {
182 	struct plic_priv *priv = d->host_data;
183 
184 	irq_domain_set_info(d, irq, hwirq, &plic_chip, d->host_data,
185 			    handle_fasteoi_irq, NULL, NULL);
186 	irq_set_noprobe(irq);
187 	irq_set_affinity(irq, &priv->lmask);
188 	return 0;
189 }
190 
191 static int plic_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
192 				 unsigned int nr_irqs, void *arg)
193 {
194 	int i, ret;
195 	irq_hw_number_t hwirq;
196 	unsigned int type;
197 	struct irq_fwspec *fwspec = arg;
198 
199 	ret = irq_domain_translate_onecell(domain, fwspec, &hwirq, &type);
200 	if (ret)
201 		return ret;
202 
203 	for (i = 0; i < nr_irqs; i++) {
204 		ret = plic_irqdomain_map(domain, virq + i, hwirq + i);
205 		if (ret)
206 			return ret;
207 	}
208 
209 	return 0;
210 }
211 
212 static const struct irq_domain_ops plic_irqdomain_ops = {
213 	.translate	= irq_domain_translate_onecell,
214 	.alloc		= plic_irq_domain_alloc,
215 	.free		= irq_domain_free_irqs_top,
216 };
217 
218 /*
219  * Handling an interrupt is a two-step process: first you claim the interrupt
220  * by reading the claim register, then you complete the interrupt by writing
221  * that source ID back to the same claim register.  This automatically enables
222  * and disables the interrupt, so there's nothing else to do.
223  */
224 static void plic_handle_irq(struct irq_desc *desc)
225 {
226 	struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
227 	struct irq_chip *chip = irq_desc_get_chip(desc);
228 	void __iomem *claim = handler->hart_base + CONTEXT_CLAIM;
229 	irq_hw_number_t hwirq;
230 
231 	WARN_ON_ONCE(!handler->present);
232 
233 	chained_irq_enter(chip, desc);
234 
235 	while ((hwirq = readl(claim))) {
236 		int irq = irq_find_mapping(handler->priv->irqdomain, hwirq);
237 
238 		if (unlikely(irq <= 0))
239 			pr_warn_ratelimited("can't find mapping for hwirq %lu\n",
240 					hwirq);
241 		else
242 			generic_handle_irq(irq);
243 	}
244 
245 	chained_irq_exit(chip, desc);
246 }
247 
248 static void plic_set_threshold(struct plic_handler *handler, u32 threshold)
249 {
250 	/* priority must be > threshold to trigger an interrupt */
251 	writel(threshold, handler->hart_base + CONTEXT_THRESHOLD);
252 }
253 
254 static int plic_dying_cpu(unsigned int cpu)
255 {
256 	if (plic_parent_irq)
257 		disable_percpu_irq(plic_parent_irq);
258 
259 	return 0;
260 }
261 
262 static int plic_starting_cpu(unsigned int cpu)
263 {
264 	struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
265 
266 	if (plic_parent_irq)
267 		enable_percpu_irq(plic_parent_irq,
268 				  irq_get_trigger_type(plic_parent_irq));
269 	else
270 		pr_warn("cpu%d: parent irq not available\n", cpu);
271 	plic_set_threshold(handler, PLIC_ENABLE_THRESHOLD);
272 
273 	return 0;
274 }
275 
276 static int __init plic_init(struct device_node *node,
277 		struct device_node *parent)
278 {
279 	int error = 0, nr_contexts, nr_handlers = 0, i;
280 	u32 nr_irqs;
281 	struct plic_priv *priv;
282 	struct plic_handler *handler;
283 
284 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
285 	if (!priv)
286 		return -ENOMEM;
287 
288 	priv->regs = of_iomap(node, 0);
289 	if (WARN_ON(!priv->regs)) {
290 		error = -EIO;
291 		goto out_free_priv;
292 	}
293 
294 	error = -EINVAL;
295 	of_property_read_u32(node, "riscv,ndev", &nr_irqs);
296 	if (WARN_ON(!nr_irqs))
297 		goto out_iounmap;
298 
299 	nr_contexts = of_irq_count(node);
300 	if (WARN_ON(!nr_contexts))
301 		goto out_iounmap;
302 
303 	error = -ENOMEM;
304 	priv->irqdomain = irq_domain_add_linear(node, nr_irqs + 1,
305 			&plic_irqdomain_ops, priv);
306 	if (WARN_ON(!priv->irqdomain))
307 		goto out_iounmap;
308 
309 	for (i = 0; i < nr_contexts; i++) {
310 		struct of_phandle_args parent;
311 		irq_hw_number_t hwirq;
312 		int cpu, hartid;
313 
314 		if (of_irq_parse_one(node, i, &parent)) {
315 			pr_err("failed to parse parent for context %d.\n", i);
316 			continue;
317 		}
318 
319 		/*
320 		 * Skip contexts other than external interrupts for our
321 		 * privilege level.
322 		 */
323 		if (parent.args[0] != RV_IRQ_EXT)
324 			continue;
325 
326 		hartid = riscv_of_parent_hartid(parent.np);
327 		if (hartid < 0) {
328 			pr_warn("failed to parse hart ID for context %d.\n", i);
329 			continue;
330 		}
331 
332 		cpu = riscv_hartid_to_cpuid(hartid);
333 		if (cpu < 0) {
334 			pr_warn("Invalid cpuid for context %d\n", i);
335 			continue;
336 		}
337 
338 		/* Find parent domain and register chained handler */
339 		if (!plic_parent_irq && irq_find_host(parent.np)) {
340 			plic_parent_irq = irq_of_parse_and_map(node, i);
341 			if (plic_parent_irq)
342 				irq_set_chained_handler(plic_parent_irq,
343 							plic_handle_irq);
344 		}
345 
346 		/*
347 		 * When running in M-mode we need to ignore the S-mode handler.
348 		 * Here we assume it always comes later, but that might be a
349 		 * little fragile.
350 		 */
351 		handler = per_cpu_ptr(&plic_handlers, cpu);
352 		if (handler->present) {
353 			pr_warn("handler already present for context %d.\n", i);
354 			plic_set_threshold(handler, PLIC_DISABLE_THRESHOLD);
355 			goto done;
356 		}
357 
358 		cpumask_set_cpu(cpu, &priv->lmask);
359 		handler->present = true;
360 		handler->hart_base =
361 			priv->regs + CONTEXT_BASE + i * CONTEXT_PER_HART;
362 		raw_spin_lock_init(&handler->enable_lock);
363 		handler->enable_base =
364 			priv->regs + ENABLE_BASE + i * ENABLE_PER_HART;
365 		handler->priv = priv;
366 done:
367 		for (hwirq = 1; hwirq <= nr_irqs; hwirq++)
368 			plic_toggle(handler, hwirq, 0);
369 		nr_handlers++;
370 	}
371 
372 	/*
373 	 * We can have multiple PLIC instances so setup cpuhp state only
374 	 * when context handler for current/boot CPU is present.
375 	 */
376 	handler = this_cpu_ptr(&plic_handlers);
377 	if (handler->present && !plic_cpuhp_setup_done) {
378 		cpuhp_setup_state(CPUHP_AP_IRQ_SIFIVE_PLIC_STARTING,
379 				  "irqchip/sifive/plic:starting",
380 				  plic_starting_cpu, plic_dying_cpu);
381 		plic_cpuhp_setup_done = true;
382 	}
383 
384 	pr_info("%pOFP: mapped %d interrupts with %d handlers for"
385 		" %d contexts.\n", node, nr_irqs, nr_handlers, nr_contexts);
386 	return 0;
387 
388 out_iounmap:
389 	iounmap(priv->regs);
390 out_free_priv:
391 	kfree(priv);
392 	return error;
393 }
394 
395 IRQCHIP_DECLARE(sifive_plic, "sifive,plic-1.0.0", plic_init);
396 IRQCHIP_DECLARE(riscv_plic0, "riscv,plic0", plic_init); /* for legacy systems */
397