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Commit 45ed285b authored by Paul Mundt's avatar Paul Mundt Committed by Paul Mundt
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sh: speculative execution support for SH7780. 



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: default avatarPaul Mundt <lethal@linux-sh.org>
parent fc31b809

arch/sh/Kconfig

+10 −0
Original line number Diff line number Diff line
@@ -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

arch/sh/kernel/cpu/init.c

+19 −0
Original line number Diff line number Diff line
@@ -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();

}