1 /*
2  * Open Multi-Processor Interrupt Controller driver
3  *
4  * Copyright (C) 2014 Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
5  * Copyright (C) 2017 Stafford Horne <shorne@gmail.com>
6  *
7  * This file is licensed under the terms of the GNU General Public License
8  * version 2.  This program is licensed "as is" without any warranty of any
9  * kind, whether express or implied.
10  *
11  * The ompic device handles IPI communication between cores in multi-core
12  * OpenRISC systems.
13  *
14  * Registers
15  *
16  * For each CPU the ompic has 2 registers. The control register for sending
17  * and acking IPIs and the status register for receiving IPIs. The register
18  * layouts are as follows:
19  *
20  *  Control register
21  *  +---------+---------+----------+---------+
22  *  | 31      | 30      | 29 .. 16 | 15 .. 0 |
23  *  ----------+---------+----------+----------
24  *  | IRQ ACK | IRQ GEN | DST CORE | DATA    |
25  *  +---------+---------+----------+---------+
26  *
27  *  Status register
28  *  +----------+-------------+----------+---------+
29  *  | 31       | 30          | 29 .. 16 | 15 .. 0 |
30  *  -----------+-------------+----------+---------+
31  *  | Reserved | IRQ Pending | SRC CORE | DATA    |
32  *  +----------+-------------+----------+---------+
33  *
34  * Architecture
35  *
36  * - The ompic generates a level interrupt to the CPU PIC when a message is
37  *   ready.  Messages are delivered via the memory bus.
38  * - The ompic does not have any interrupt input lines.
39  * - The ompic is wired to the same irq line on each core.
40  * - Devices are wired to the same irq line on each core.
41  *
42  *   +---------+                         +---------+
43  *   | CPU     |                         | CPU     |
44  *   |  Core 0 |<==\ (memory access) /==>|  Core 1 |
45  *   |  [ PIC ]|   |                 |   |  [ PIC ]|
46  *   +----^-^--+   |                 |   +----^-^--+
47  *        | |      v                 v        | |
48  *   <====|=|=================================|=|==> (memory bus)
49  *        | |      ^                  ^       | |
50  *  (ipi  | +------|---------+--------|-------|-+ (device irq)
51  *   irq  |        |         |        |       |
52  *  core0)| +------|---------|--------|-------+ (ipi irq core1)
53  *        | |      |         |        |
54  *   +----o-o-+    |    +--------+    |
55  *   | ompic  |<===/    | Device |<===/
56  *   |  IPI   |         +--------+
57  *   +--------+*
58  *
59  */
60 
61 #include <linux/io.h>
62 #include <linux/ioport.h>
63 #include <linux/interrupt.h>
64 #include <linux/smp.h>
65 #include <linux/of.h>
66 #include <linux/of_irq.h>
67 #include <linux/of_address.h>
68 
69 #include <linux/irqchip.h>
70 
71 #define OMPIC_CPUBYTES		8
72 #define OMPIC_CTRL(cpu)		(0x0 + (cpu * OMPIC_CPUBYTES))
73 #define OMPIC_STAT(cpu)		(0x4 + (cpu * OMPIC_CPUBYTES))
74 
75 #define OMPIC_CTRL_IRQ_ACK	(1 << 31)
76 #define OMPIC_CTRL_IRQ_GEN	(1 << 30)
77 #define OMPIC_CTRL_DST(cpu)	(((cpu) & 0x3fff) << 16)
78 
79 #define OMPIC_STAT_IRQ_PENDING	(1 << 30)
80 
81 #define OMPIC_DATA(x)		((x) & 0xffff)
82 
83 DEFINE_PER_CPU(unsigned long, ops);
84 
85 static void __iomem *ompic_base;
86 
ompic_readreg(void __iomem * base,loff_t offset)87 static inline u32 ompic_readreg(void __iomem *base, loff_t offset)
88 {
89 	return ioread32be(base + offset);
90 }
91 
ompic_writereg(void __iomem * base,loff_t offset,u32 data)92 static void ompic_writereg(void __iomem *base, loff_t offset, u32 data)
93 {
94 	iowrite32be(data, base + offset);
95 }
96 
ompic_raise_softirq(const struct cpumask * mask,unsigned int ipi_msg)97 static void ompic_raise_softirq(const struct cpumask *mask,
98 				unsigned int ipi_msg)
99 {
100 	unsigned int dst_cpu;
101 	unsigned int src_cpu = smp_processor_id();
102 
103 	for_each_cpu(dst_cpu, mask) {
104 		set_bit(ipi_msg, &per_cpu(ops, dst_cpu));
105 
106 		/*
107 		 * On OpenRISC the atomic set_bit() call implies a memory
108 		 * barrier.  Otherwise we would need: smp_wmb(); paired
109 		 * with the read in ompic_ipi_handler.
110 		 */
111 
112 		ompic_writereg(ompic_base, OMPIC_CTRL(src_cpu),
113 			       OMPIC_CTRL_IRQ_GEN |
114 			       OMPIC_CTRL_DST(dst_cpu) |
115 			       OMPIC_DATA(1));
116 	}
117 }
118 
ompic_ipi_handler(int irq,void * dev_id)119 static irqreturn_t ompic_ipi_handler(int irq, void *dev_id)
120 {
121 	unsigned int cpu = smp_processor_id();
122 	unsigned long *pending_ops = &per_cpu(ops, cpu);
123 	unsigned long ops;
124 
125 	ompic_writereg(ompic_base, OMPIC_CTRL(cpu), OMPIC_CTRL_IRQ_ACK);
126 	while ((ops = xchg(pending_ops, 0)) != 0) {
127 
128 		/*
129 		 * On OpenRISC the atomic xchg() call implies a memory
130 		 * barrier.  Otherwise we may need an smp_rmb(); paired
131 		 * with the write in ompic_raise_softirq.
132 		 */
133 
134 		do {
135 			unsigned long ipi_msg;
136 
137 			ipi_msg = __ffs(ops);
138 			ops &= ~(1UL << ipi_msg);
139 
140 			handle_IPI(ipi_msg);
141 		} while (ops);
142 	}
143 
144 	return IRQ_HANDLED;
145 }
146 
ompic_of_init(struct device_node * node,struct device_node * parent)147 static int __init ompic_of_init(struct device_node *node,
148 				struct device_node *parent)
149 {
150 	struct resource res;
151 	int irq;
152 	int ret;
153 
154 	/* Validate the DT */
155 	if (ompic_base) {
156 		pr_err("ompic: duplicate ompic's are not supported");
157 		return -EEXIST;
158 	}
159 
160 	if (of_address_to_resource(node, 0, &res)) {
161 		pr_err("ompic: reg property requires an address and size");
162 		return -EINVAL;
163 	}
164 
165 	if (resource_size(&res) < (num_possible_cpus() * OMPIC_CPUBYTES)) {
166 		pr_err("ompic: reg size, currently %d must be at least %d",
167 			resource_size(&res),
168 			(num_possible_cpus() * OMPIC_CPUBYTES));
169 		return -EINVAL;
170 	}
171 
172 	/* Setup the device */
173 	ompic_base = ioremap(res.start, resource_size(&res));
174 	if (!ompic_base) {
175 		pr_err("ompic: unable to map registers");
176 		return -ENOMEM;
177 	}
178 
179 	irq = irq_of_parse_and_map(node, 0);
180 	if (irq <= 0) {
181 		pr_err("ompic: unable to parse device irq");
182 		ret = -EINVAL;
183 		goto out_unmap;
184 	}
185 
186 	ret = request_irq(irq, ompic_ipi_handler, IRQF_PERCPU,
187 				"ompic_ipi", NULL);
188 	if (ret)
189 		goto out_irq_disp;
190 
191 	set_smp_cross_call(ompic_raise_softirq);
192 
193 	return 0;
194 
195 out_irq_disp:
196 	irq_dispose_mapping(irq);
197 out_unmap:
198 	iounmap(ompic_base);
199 	ompic_base = NULL;
200 	return ret;
201 }
202 IRQCHIP_DECLARE(ompic, "openrisc,ompic", ompic_of_init);
203