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authorRichard Henderson <rth@twiddle.net>2013-07-12 09:36:21 -0700
committerMatt Turner <mattst88@gmail.com>2013-11-16 16:33:15 -0800
commit7f3bbb82e0c371d6881129f776c90130ba66f051 (patch)
treee2bb143c17545c720484602fbaa829eae2e66119 /arch/alpha/Kconfig
parentfddd87d6e135924b92499917bace103e46c22d00 (diff)
alpha: Primitive support for CPU power down.
Use WTINT to wait for the next interrupt. Squash the WTINT call if the PALcode doesn't support it (e.g. MILO). No attempt is yet made to skip clock ticks during normal scheduling in order to stay in power down mode longer. Signed-off-by: Richard Henderson <rth@twiddle.net>
Diffstat (limited to 'arch/alpha/Kconfig')
-rw-r--r--arch/alpha/Kconfig24
1 files changed, 24 insertions, 0 deletions
diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
index a67b971c830a..f9e84da49716 100644
--- a/arch/alpha/Kconfig
+++ b/arch/alpha/Kconfig
@@ -586,6 +586,30 @@ config NUMA
Access). This option is for configuring high-end multiprocessor
server machines. If in doubt, say N.
+config ALPHA_WTINT
+ bool "Use WTINT" if ALPHA_SRM || ALPHA_GENERIC
+ default y if ALPHA_QEMU
+ default n if ALPHA_EV5 || ALPHA_EV56 || (ALPHA_EV4 && !ALPHA_LCA)
+ default n if !ALPHA_SRM && !ALPHA_GENERIC
+ default y if SMP
+ ---help---
+ The Wait for Interrupt (WTINT) PALcall attempts to place the CPU
+ to sleep until the next interrupt. This may reduce the power
+ consumed, and the heat produced by the computer. However, it has
+ the side effect of making the cycle counter unreliable as a timing
+ device across the sleep.
+
+ For emulation under QEMU, definitely say Y here, as we have other
+ mechanisms for measuring time than the cycle counter.
+
+ For EV4 (but not LCA), EV5 and EV56 systems, or for systems running
+ MILO, sleep mode is not supported so you might as well say N here.
+
+ For SMP systems we cannot use the cycle counter for timing anyway,
+ so you might as well say Y here.
+
+ If unsure, say N.
+
config NODES_SHIFT
int
default "7"