1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright 2016 IBM Corporation.
4  */
5 #include <linux/types.h>
6 #include <linux/kernel.h>
7 #include <linux/irq.h>
8 #include <linux/smp.h>
9 #include <linux/interrupt.h>
10 #include <linux/irqdomain.h>
11 #include <linux/cpu.h>
12 #include <linux/of.h>
13 
14 #include <asm/smp.h>
15 #include <asm/irq.h>
16 #include <asm/errno.h>
17 #include <asm/xics.h>
18 #include <asm/io.h>
19 #include <asm/opal.h>
20 #include <asm/kvm_ppc.h>
21 
22 static void icp_opal_teardown_cpu(void)
23 {
24 	int hw_cpu = hard_smp_processor_id();
25 
26 	/* Clear any pending IPI */
27 	opal_int_set_mfrr(hw_cpu, 0xff);
28 }
29 
30 static void icp_opal_flush_ipi(void)
31 {
32 	/*
33 	 * We take the ipi irq but and never return so we need to EOI the IPI,
34 	 * but want to leave our priority 0.
35 	 *
36 	 * Should we check all the other interrupts too?
37 	 * Should we be flagging idle loop instead?
38 	 * Or creating some task to be scheduled?
39 	 */
40 	if (opal_int_eoi((0x00 << 24) | XICS_IPI) > 0)
41 		force_external_irq_replay();
42 }
43 
44 static unsigned int icp_opal_get_xirr(void)
45 {
46 	unsigned int kvm_xirr;
47 	__be32 hw_xirr;
48 	int64_t rc;
49 
50 	/* Handle an interrupt latched by KVM first */
51 	kvm_xirr = kvmppc_get_xics_latch();
52 	if (kvm_xirr)
53 		return kvm_xirr;
54 
55 	/* Then ask OPAL */
56 	rc = opal_int_get_xirr(&hw_xirr, false);
57 	if (rc < 0)
58 		return 0;
59 	return be32_to_cpu(hw_xirr);
60 }
61 
62 static unsigned int icp_opal_get_irq(void)
63 {
64 	unsigned int xirr;
65 	unsigned int vec;
66 	unsigned int irq;
67 
68 	xirr = icp_opal_get_xirr();
69 	vec = xirr & 0x00ffffff;
70 	if (vec == XICS_IRQ_SPURIOUS)
71 		return 0;
72 
73 	irq = irq_find_mapping(xics_host, vec);
74 	if (likely(irq)) {
75 		xics_push_cppr(vec);
76 		return irq;
77 	}
78 
79 	/* We don't have a linux mapping, so have rtas mask it. */
80 	xics_mask_unknown_vec(vec);
81 
82 	/* We might learn about it later, so EOI it */
83 	if (opal_int_eoi(xirr) > 0)
84 		force_external_irq_replay();
85 
86 	return 0;
87 }
88 
89 static void icp_opal_set_cpu_priority(unsigned char cppr)
90 {
91 	/*
92 	 * Here be dragons. The caller has asked to allow only IPI's and not
93 	 * external interrupts. But OPAL XIVE doesn't support that. So instead
94 	 * of allowing no interrupts allow all. That's still not right, but
95 	 * currently the only caller who does this is xics_migrate_irqs_away()
96 	 * and it works in that case.
97 	 */
98 	if (cppr >= DEFAULT_PRIORITY)
99 		cppr = LOWEST_PRIORITY;
100 
101 	xics_set_base_cppr(cppr);
102 	opal_int_set_cppr(cppr);
103 	iosync();
104 }
105 
106 static void icp_opal_eoi(struct irq_data *d)
107 {
108 	unsigned int hw_irq = (unsigned int)irqd_to_hwirq(d);
109 	int64_t rc;
110 
111 	iosync();
112 	rc = opal_int_eoi((xics_pop_cppr() << 24) | hw_irq);
113 
114 	/*
115 	 * EOI tells us whether there are more interrupts to fetch.
116 	 *
117 	 * Some HW implementations might not be able to send us another
118 	 * external interrupt in that case, so we force a replay.
119 	 */
120 	if (rc > 0)
121 		force_external_irq_replay();
122 }
123 
124 #ifdef CONFIG_SMP
125 
126 static void icp_opal_cause_ipi(int cpu)
127 {
128 	int hw_cpu = get_hard_smp_processor_id(cpu);
129 
130 	kvmppc_set_host_ipi(cpu);
131 	opal_int_set_mfrr(hw_cpu, IPI_PRIORITY);
132 }
133 
134 static irqreturn_t icp_opal_ipi_action(int irq, void *dev_id)
135 {
136 	int cpu = smp_processor_id();
137 
138 	kvmppc_clear_host_ipi(cpu);
139 	opal_int_set_mfrr(get_hard_smp_processor_id(cpu), 0xff);
140 
141 	return smp_ipi_demux();
142 }
143 
144 /*
145  * Called when an interrupt is received on an off-line CPU to
146  * clear the interrupt, so that the CPU can go back to nap mode.
147  */
148 void icp_opal_flush_interrupt(void)
149 {
150 	unsigned int xirr;
151 	unsigned int vec;
152 
153 	do {
154 		xirr = icp_opal_get_xirr();
155 		vec = xirr & 0x00ffffff;
156 		if (vec == XICS_IRQ_SPURIOUS)
157 			break;
158 		if (vec == XICS_IPI) {
159 			/* Clear pending IPI */
160 			int cpu = smp_processor_id();
161 			kvmppc_clear_host_ipi(cpu);
162 			opal_int_set_mfrr(get_hard_smp_processor_id(cpu), 0xff);
163 		} else {
164 			pr_err("XICS: hw interrupt 0x%x to offline cpu, "
165 			       "disabling\n", vec);
166 			xics_mask_unknown_vec(vec);
167 		}
168 
169 		/* EOI the interrupt */
170 	} while (opal_int_eoi(xirr) > 0);
171 }
172 
173 #endif /* CONFIG_SMP */
174 
175 static const struct icp_ops icp_opal_ops = {
176 	.get_irq	= icp_opal_get_irq,
177 	.eoi		= icp_opal_eoi,
178 	.set_priority	= icp_opal_set_cpu_priority,
179 	.teardown_cpu	= icp_opal_teardown_cpu,
180 	.flush_ipi	= icp_opal_flush_ipi,
181 #ifdef CONFIG_SMP
182 	.ipi_action	= icp_opal_ipi_action,
183 	.cause_ipi	= icp_opal_cause_ipi,
184 #endif
185 };
186 
187 int icp_opal_init(void)
188 {
189 	struct device_node *np;
190 
191 	np = of_find_compatible_node(NULL, NULL, "ibm,opal-intc");
192 	if (!np)
193 		return -ENODEV;
194 
195 	icp_ops = &icp_opal_ops;
196 
197 	printk("XICS: Using OPAL ICP fallbacks\n");
198 
199 	return 0;
200 }
201 
202