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 #include <mach/ep93xx-regs.h>
20 #include <asm/thread_notify.h>
21 
22 struct crunch_state *crunch_owner;
23 
crunch_task_release(struct thread_info * thread)24 void crunch_task_release(struct thread_info *thread)
25 {
26 	local_irq_disable();
27 	if (crunch_owner == &thread->crunchstate)
28 		crunch_owner = NULL;
29 	local_irq_enable();
30 }
31 
crunch_enabled(u32 devcfg)32 static int crunch_enabled(u32 devcfg)
33 {
34 	return !!(devcfg & EP93XX_SYSCON_DEVCFG_CPENA);
35 }
36 
crunch_do(struct notifier_block * self,unsigned long cmd,void * t)37 static int crunch_do(struct notifier_block *self, unsigned long cmd, void *t)
38 {
39 	struct thread_info *thread = (struct thread_info *)t;
40 	struct crunch_state *crunch_state;
41 	u32 devcfg;
42 
43 	crunch_state = &thread->crunchstate;
44 
45 	switch (cmd) {
46 	case THREAD_NOTIFY_FLUSH:
47 		memset(crunch_state, 0, sizeof(*crunch_state));
48 
49 		/*
50 		 * FALLTHROUGH: Ensure we don't try to overwrite our newly
51 		 * initialised state information on the first fault.
52 		 */
53 
54 	case THREAD_NOTIFY_EXIT:
55 		crunch_task_release(thread);
56 		break;
57 
58 	case THREAD_NOTIFY_SWITCH:
59 		devcfg = __raw_readl(EP93XX_SYSCON_DEVCFG);
60 		if (crunch_enabled(devcfg) || crunch_owner == crunch_state) {
61 			/*
62 			 * We don't use ep93xx_syscon_swlocked_write() here
63 			 * because we are on the context switch path and
64 			 * preemption is already disabled.
65 			 */
66 			devcfg ^= EP93XX_SYSCON_DEVCFG_CPENA;
67 			__raw_writel(0xaa, EP93XX_SYSCON_SWLOCK);
68 			__raw_writel(devcfg, EP93XX_SYSCON_DEVCFG);
69 		}
70 		break;
71 	}
72 
73 	return NOTIFY_DONE;
74 }
75 
76 static struct notifier_block crunch_notifier_block = {
77 	.notifier_call	= crunch_do,
78 };
79 
crunch_init(void)80 static int __init crunch_init(void)
81 {
82 	thread_register_notifier(&crunch_notifier_block);
83 	elf_hwcap |= HWCAP_CRUNCH;
84 
85 	return 0;
86 }
87 
88 late_initcall(crunch_init);
89