1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright 2010 2011 Mark Nelson and Tseng-Hui (Frank) Lin, IBM Corporation
4  */
5 
6 #include <linux/errno.h>
7 #include <linux/slab.h>
8 #include <linux/export.h>
9 #include <linux/irq.h>
10 #include <linux/interrupt.h>
11 #include <linux/of.h>
12 #include <linux/list.h>
13 #include <linux/notifier.h>
14 
15 #include <asm/machdep.h>
16 #include <asm/rtas.h>
17 #include <asm/irq.h>
18 #include <asm/io_event_irq.h>
19 
20 #include "pseries.h"
21 
22 /*
23  * IO event interrupt is a mechanism provided by RTAS to return
24  * information about hardware error and non-error events. Device
25  * drivers can register their event handlers to receive events.
26  * Device drivers are expected to use atomic_notifier_chain_register()
27  * and atomic_notifier_chain_unregister() to register and unregister
28  * their event handlers. Since multiple IO event types and scopes
29  * share an IO event interrupt, the event handlers are called one
30  * by one until the IO event is claimed by one of the handlers.
31  * The event handlers are expected to return NOTIFY_OK if the
32  * event is handled by the event handler or NOTIFY_DONE if the
33  * event does not belong to the handler.
34  *
35  * Usage:
36  *
37  * Notifier function:
38  * #include <asm/io_event_irq.h>
39  * int event_handler(struct notifier_block *nb, unsigned long val, void *data) {
40  * 	p = (struct pseries_io_event_sect_data *) data;
41  * 	if (! is_my_event(p->scope, p->event_type)) return NOTIFY_DONE;
42  * 		:
43  * 		:
44  * 	return NOTIFY_OK;
45  * }
46  * struct notifier_block event_nb = {
47  * 	.notifier_call = event_handler,
48  * }
49  *
50  * Registration:
51  * atomic_notifier_chain_register(&pseries_ioei_notifier_list, &event_nb);
52  *
53  * Unregistration:
54  * atomic_notifier_chain_unregister(&pseries_ioei_notifier_list, &event_nb);
55  */
56 
57 ATOMIC_NOTIFIER_HEAD(pseries_ioei_notifier_list);
58 EXPORT_SYMBOL_GPL(pseries_ioei_notifier_list);
59 
60 static int ioei_check_exception_token;
61 
62 static char ioei_rtas_buf[RTAS_DATA_BUF_SIZE] __cacheline_aligned;
63 
64 /**
65  * Find the data portion of an IO Event section from event log.
66  * @elog: RTAS error/event log.
67  *
68  * Return:
69  * 	pointer to a valid IO event section data. NULL if not found.
70  */
71 static struct pseries_io_event * ioei_find_event(struct rtas_error_log *elog)
72 {
73 	struct pseries_errorlog *sect;
74 
75 	/* We should only ever get called for io-event interrupts, but if
76 	 * we do get called for another type then something went wrong so
77 	 * make some noise about it.
78 	 * RTAS_TYPE_IO only exists in extended event log version 6 or later.
79 	 * No need to check event log version.
80 	 */
81 	if (unlikely(rtas_error_type(elog) != RTAS_TYPE_IO)) {
82 		printk_once(KERN_WARNING"io_event_irq: Unexpected event type %d",
83 			    rtas_error_type(elog));
84 		return NULL;
85 	}
86 
87 	sect = get_pseries_errorlog(elog, PSERIES_ELOG_SECT_ID_IO_EVENT);
88 	if (unlikely(!sect)) {
89 		printk_once(KERN_WARNING "io_event_irq: RTAS extended event "
90 			    "log does not contain an IO Event section. "
91 			    "Could be a bug in system firmware!\n");
92 		return NULL;
93 	}
94 	return (struct pseries_io_event *) &sect->data;
95 }
96 
97 /*
98  * PAPR:
99  * - check-exception returns the first found error or event and clear that
100  *   error or event so it is reported once.
101  * - Each interrupt returns one event. If a plateform chooses to report
102  *   multiple events through a single interrupt, it must ensure that the
103  *   interrupt remains asserted until check-exception has been used to
104  *   process all out-standing events for that interrupt.
105  *
106  * Implementation notes:
107  * - Events must be processed in the order they are returned. Hence,
108  *   sequential in nature.
109  * - The owner of an event is determined by combinations of scope,
110  *   event type, and sub-type. There is no easy way to pre-sort clients
111  *   by scope or event type alone. For example, Torrent ISR route change
112  *   event is reported with scope 0x00 (Not Applicable) rather than
113  *   0x3B (Torrent-hub). It is better to let the clients to identify
114  *   who owns the event.
115  */
116 
117 static irqreturn_t ioei_interrupt(int irq, void *dev_id)
118 {
119 	struct pseries_io_event *event;
120 	int rtas_rc;
121 
122 	for (;;) {
123 		rtas_rc = rtas_call(ioei_check_exception_token, 6, 1, NULL,
124 				    RTAS_VECTOR_EXTERNAL_INTERRUPT,
125 				    virq_to_hw(irq),
126 				    RTAS_IO_EVENTS, 1 /* Time Critical */,
127 				    __pa(ioei_rtas_buf),
128 				    RTAS_DATA_BUF_SIZE);
129 		if (rtas_rc != 0)
130 			break;
131 
132 		event = ioei_find_event((struct rtas_error_log *)ioei_rtas_buf);
133 		if (!event)
134 			continue;
135 
136 		atomic_notifier_call_chain(&pseries_ioei_notifier_list,
137 					   0, event);
138 	}
139 	return IRQ_HANDLED;
140 }
141 
142 static int __init ioei_init(void)
143 {
144 	struct device_node *np;
145 
146 	ioei_check_exception_token = rtas_token("check-exception");
147 	if (ioei_check_exception_token == RTAS_UNKNOWN_SERVICE)
148 		return -ENODEV;
149 
150 	np = of_find_node_by_path("/event-sources/ibm,io-events");
151 	if (np) {
152 		request_event_sources_irqs(np, ioei_interrupt, "IO_EVENT");
153 		pr_info("IBM I/O event interrupts enabled\n");
154 		of_node_put(np);
155 	} else {
156 		return -ENODEV;
157 	}
158 	return 0;
159 }
160 machine_subsys_initcall(pseries, ioei_init);
161 
162