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authorPaul Mundt <lethal@linux-sh.org>2007-03-08 18:12:17 +0900
committerPaul Mundt <lethal@hera.kernel.org>2007-05-07 02:10:51 +0000
commit45ed285b54930767937deb0eaf718b1d08c3c475 (patch)
tree6132a0116f3c6370884d64928dbc2825b964f510 /arch/sh
parentfc31b80957a14a60513d953cc67a55519a2b09c7 (diff)
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: Paul Mundt <lethal@linux-sh.org>
Diffstat (limited to 'arch/sh')
-rw-r--r--arch/sh/Kconfig10
-rw-r--r--arch/sh/kernel/cpu/init.c19
2 files changed, 29 insertions, 0 deletions
diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index 4d16d891707..2715834f72b 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -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
diff --git a/arch/sh/kernel/cpu/init.c b/arch/sh/kernel/cpu/init.c
index 726acfcb9b7..6451ad63017 100644
--- a/arch/sh/kernel/cpu/init.c
+++ b/arch/sh/kernel/cpu/init.c
@@ -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();
}