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sh: delay slot future proofing via EXPMASK on SH-4A parts.

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This implements EXPMASK initialization code for SH-4A parts, where it is
possible to disable compat features that will go away in newer cores.
Presently this includes disabling support for non-nop instructions in the
rte delay slot, as well as a sleep instruction being placed in a delay
slot (neither of which the kernel does any longer). As a result of this,
any future offenders will have illegal slot exceptions generated for
them.

Associative writes for the memory-mapped cache array are still left
enabled, until such a point that special cache operations for SH-4A are
provided to move off of the current (and rather dated) SH-4 versions.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
This commit is contained in:
Paul Mundt 2009-08-15 07:43:21 +09:00
parent 7a90e00dda
commit 7dd6662a92
1 changed files with 33 additions and 1 deletions
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34
arch/sh/kernel/cpu/init.c
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@ -3,7 +3,7 @@
*
* CPU init code
*
* Copyright (C) 2002 - 2007 Paul Mundt
* Copyright (C) 2002 - 2009 Paul Mundt
* Copyright (C) 2003 Richard Curnow
*
* This file is subject to the terms and conditions of the GNU General Public
@ -62,6 +62,37 @@ static void __init speculative_execution_init(void)
#define speculative_execution_init() do { } while (0)
#endif
#ifdef CONFIG_CPU_SH4A
#define EXPMASK 0xff2f0004
#define EXPMASK_RTEDS (1 << 0)
#define EXPMASK_BRDSSLP (1 << 1)
#define EXPMASK_MMCAW (1 << 4)
static void __init expmask_init(void)
{
unsigned long expmask = __raw_readl(EXPMASK);
/*
* Future proofing.
*
* Disable support for slottable sleep instruction
* and non-nop instructions in the rte delay slot.
*/
expmask &= ~(EXPMASK_RTEDS | EXPMASK_BRDSSLP);
/*
* Enable associative writes to the memory-mapped cache array
* until the cache flush ops have been rewritten.
*/
expmask |= EXPMASK_MMCAW;
__raw_writel(expmask, EXPMASK);
ctrl_barrier();
}
#else
#define expmask_init() do { } while (0)
#endif
/* 2nd-level cache init */
void __uses_jump_to_uncached __attribute__ ((weak)) l2_cache_init(void)
{
@ -321,4 +352,5 @@ asmlinkage void __init sh_cpu_init(void)
#endif
speculative_execution_init();
expmask_init();
}