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sh: speculative execution support for SH7780.

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SH7780 has a speculative execution mode where it can speculatively
perform an instruction fetch for subroutine returns, this allows it
to be enabled. There are some various pitfalls associated with this
mode, so it's left as depending on CONFIG_EXPERIMENTAL and not
enabled by default.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
This commit is contained in:
Paul Mundt 2007-03-08 18:12:17 +09:00 committed by Paul Mundt
parent fc31b80957
commit 45ed285b54
2 changed files with 29 additions and 0 deletions
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10
arch/sh/Kconfig
View File

@ -366,6 +366,16 @@ config SH_STORE_QUEUES
Selecting this option will enable an in-kernel API for manipulating
the store queues integrated in the SH-4 processors.
config SPECULATIVE_EXECUTION
bool "Speculative subroutine return"
depends on CPU_SUBTYPE_SH7780 && EXPERIMENTAL
help
This enables support for a speculative instruction fetch for
subroutine return. There are various pitfalls associated with
this, as outlined in the SH7780 hardware manual.
If unsure, say N.
config CPU_HAS_INTEVT
bool

19
arch/sh/kernel/cpu/init.c
View File

@ -41,6 +41,23 @@ __setup("no" __stringify(x), x##_setup);
onchip_setup(fpu);
onchip_setup(dsp);
#ifdef CONFIG_SPECULATIVE_EXECUTION
#define CPUOPM 0xff2f0000
#define CPUOPM_RABD (1 << 5)
static void __init speculative_execution_init(void)
{
/* Clear RABD */
ctrl_outl(ctrl_inl(CPUOPM) & ~CPUOPM_RABD, CPUOPM);
/* Flush the update */
(void)ctrl_inl(CPUOPM);
ctrl_barrier();
}
#else
#define speculative_execution_init() do { } while (0)
#endif
/*
* Generic first-level cache init
*/
@ -261,4 +278,6 @@ asmlinkage void __init sh_cpu_init(void)
*/
ubc_wakeup();
#endif
speculative_execution_init();
}