linux/arch/arm/kernel/xscale-cp0.c
Russell King 797245f5da ARM: Convert VFP/Crunch/XscaleCP thread_release() to exit_thread()
This avoids races in the VFP code where the dead thread may have
state on another CPU.  By moving this code to exit_thread(), we
will be running as the thread, and therefore be running on the
current CPU.

This means that we can ensure that the only local state is accessed
in the thread notifiers.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2009-12-18 14:53:41 +00:00

180 lines
3.9 KiB
C

/*
* 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/module.h>
#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
printk(KERN_WARNING "CAUTION: XScale iWMMXt coprocessor "
"detected, but kernel support is missing.\n");
#else
printk(KERN_INFO "XScale iWMMXt coprocessor detected.\n");
elf_hwcap |= HWCAP_IWMMXT;
thread_register_notifier(&iwmmxt_notifier_block);
#endif
} else {
printk(KERN_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);