1 /*
2  * arch/arm/kernel/crunch.c
3  * Cirrus MaverickCrunch context switching and handling
4  *
5  * Copyright (C) 2006 Lennert Buytenhek <buytenh@wantstofly.org>
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License version 2 as
9  * published by the Free Software Foundation.
10  */
11 
12 #include <linux/module.h>
13 #include <linux/types.h>
14 #include <linux/kernel.h>
15 #include <linux/signal.h>
16 #include <linux/sched.h>
17 #include <linux/init.h>
18 #include <linux/io.h>
19 
20 #include <asm/thread_notify.h>
21 
22 #include "soc.h"
23 
24 struct crunch_state *crunch_owner;
25 
crunch_task_release(struct thread_info * thread)26 void crunch_task_release(struct thread_info *thread)
27 {
28 	local_irq_disable();
29 	if (crunch_owner == &thread->crunchstate)
30 		crunch_owner = NULL;
31 	local_irq_enable();
32 }
33 
crunch_enabled(u32 devcfg)34 static int crunch_enabled(u32 devcfg)
35 {
36 	return !!(devcfg & EP93XX_SYSCON_DEVCFG_CPENA);
37 }
38 
crunch_do(struct notifier_block * self,unsigned long cmd,void * t)39 static int crunch_do(struct notifier_block *self, unsigned long cmd, void *t)
40 {
41 	struct thread_info *thread = (struct thread_info *)t;
42 	struct crunch_state *crunch_state;
43 	u32 devcfg;
44 
45 	crunch_state = &thread->crunchstate;
46 
47 	switch (cmd) {
48 	case THREAD_NOTIFY_FLUSH:
49 		memset(crunch_state, 0, sizeof(*crunch_state));
50 
51 		/*
52 		 * FALLTHROUGH: Ensure we don't try to overwrite our newly
53 		 * initialised state information on the first fault.
54 		 */
55 
56 	case THREAD_NOTIFY_EXIT:
57 		crunch_task_release(thread);
58 		break;
59 
60 	case THREAD_NOTIFY_SWITCH:
61 		devcfg = __raw_readl(EP93XX_SYSCON_DEVCFG);
62 		if (crunch_enabled(devcfg) || crunch_owner == crunch_state) {
63 			/*
64 			 * We don't use ep93xx_syscon_swlocked_write() here
65 			 * because we are on the context switch path and
66 			 * preemption is already disabled.
67 			 */
68 			devcfg ^= EP93XX_SYSCON_DEVCFG_CPENA;
69 			__raw_writel(0xaa, EP93XX_SYSCON_SWLOCK);
70 			__raw_writel(devcfg, EP93XX_SYSCON_DEVCFG);
71 		}
72 		break;
73 	}
74 
75 	return NOTIFY_DONE;
76 }
77 
78 static struct notifier_block crunch_notifier_block = {
79 	.notifier_call	= crunch_do,
80 };
81 
crunch_init(void)82 int __init crunch_init(void)
83 {
84 	thread_register_notifier(&crunch_notifier_block);
85 	elf_hwcap |= HWCAP_CRUNCH;
86 
87 	return 0;
88 }
89