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/*
* linux/arch/arm/kernel/xscale-cp0.c
*
* XScale DSP and iWMMXt coprocessor context switching and handling
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/io.h>
#include <asm/thread_notify.h>
static inline void dsp_save_state(u32 *state)
{
__asm__ __volatile__ (
"mrrc p0, 0, %0, %1, c0\n"
: "=r" (state[0]), "=r" (state[1]));
}
static inline void dsp_load_state(u32 *state)
{
__asm__ __volatile__ (
"mcrr p0, 0, %0, %1, c0\n"
: : "r" (state[0]), "r" (state[1]));
}
static int dsp_do(struct notifier_block *self, unsigned long cmd, void *t)
{
struct thread_info *thread = t;
switch (cmd) {
case THREAD_NOTIFY_FLUSH:
thread->cpu_context.extra[0] = 0;
thread->cpu_context.extra[1] = 0;
break;
case THREAD_NOTIFY_SWITCH:
dsp_save_state(current_thread_info()->cpu_context.extra);
dsp_load_state(thread->cpu_context.extra);
break;
}
return NOTIFY_DONE;
}
static struct notifier_block dsp_notifier_block = {
.notifier_call = dsp_do,
};
#ifdef CONFIG_IWMMXT
static int iwmmxt_do(struct notifier_block *self, unsigned long cmd, void *t)
{
struct thread_info *thread = t;
switch (cmd) {
case THREAD_NOTIFY_FLUSH:
/*
* flush_thread() zeroes thread->fpstate, so no need
* to do anything here.
*
* FALLTHROUGH: Ensure we don't try to overwrite our newly
* initialised state information on the first fault.
*/
case THREAD_NOTIFY_EXIT:
iwmmxt_task_release(thread);
break;
case THREAD_NOTIFY_SWITCH:
iwmmxt_task_switch(thread);
break;
}
return NOTIFY_DONE;
}
static struct notifier_block iwmmxt_notifier_block = {
.notifier_call = iwmmxt_do,
};
#endif
static u32 __init xscale_cp_access_read(void)
{
u32 value;
__asm__ __volatile__ (
"mrc p15, 0, %0, c15, c1, 0\n\t"
: "=r" (value));
return value;
}
static void __init xscale_cp_access_write(u32 value)
{
u32 temp;
__asm__ __volatile__ (
"mcr p15, 0, %1, c15, c1, 0\n\t"
"mrc p15, 0, %0, c15, c1, 0\n\t"
"mov %0, %0\n\t"
"sub pc, pc, #4\n\t"
: "=r" (temp) : "r" (value));
}
/*
* Detect whether we have a MAC coprocessor (40 bit register) or an
* iWMMXt coprocessor (64 bit registers) by loading 00000100:00000000
* into a coprocessor register and reading it back, and checking
* whether the upper word survived intact.
*/
static int __init cpu_has_iwmmxt(void)
{
u32 lo;
u32 hi;
/*
* This sequence is interpreted by the DSP coprocessor as:
* mar acc0, %2, %3
* mra %0, %1, acc0
*
* And by the iWMMXt coprocessor as:
* tmcrr wR0, %2, %3
* tmrrc %0, %1, wR0
*/
__asm__ __volatile__ (
"mcrr p0, 0, %2, %3, c0\n"
"mrrc p0, 0, %0, %1, c0\n"
: "=r" (lo), "=r" (hi)
: "r" (0), "r" (0x100));
return !!hi;
}
/*
* If we detect that the CPU has iWMMXt (and CONFIG_IWMMXT=y), we
* disable CP0/CP1 on boot, and let call_fpe() and the iWMMXt lazy
* switch code handle iWMMXt context switching. If on the other
* hand the CPU has a DSP coprocessor, we keep access to CP0 enabled
* all the time, and save/restore acc0 on context switch in non-lazy
* fashion.
*/
static int __init xscale_cp0_init(void)
{
u32 cp_access;
cp_access = xscale_cp_access_read() & ~3;
xscale_cp_access_write(cp_access | 1);
if (cpu_has_iwmmxt()) {
#ifndef CONFIG_IWMMXT
pr_warn("CAUTION: XScale iWMMXt coprocessor detected, but kernel support is missing.\n");
#else
pr_info("XScale iWMMXt coprocessor detected.\n");
elf_hwcap |= HWCAP_IWMMXT;
thread_register_notifier(&iwmmxt_notifier_block);
#endif
} else {
pr_info("XScale DSP coprocessor detected.\n");
thread_register_notifier(&dsp_notifier_block);
cp_access |= 1;
}
xscale_cp_access_write(cp_access);
return 0;
}
late_initcall(xscale_cp0_init);
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