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authorVaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>2013-09-06 00:25:06 +0530
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-09-26 17:18:01 -0700
commitd08bfff9ef39c029befa68b2641ad2f7a2c894b6 (patch)
tree1e8050f424710f962a89c9fcb466eef9bbc73201 /arch/powerpc/platforms/pseries/setup.c
parentd8ba750f9a2feb07bb6f0448807907b674ca4525 (diff)
downloadlinaro-lsk-d08bfff9ef39c029befa68b2641ad2f7a2c894b6.tar.gz
powerpc: Default arch idle could cede processor on pseries
commit 363edbe2614aa90df706c0f19ccfa2a6c06af0be upstream. When adding cpuidle support to pSeries, we introduced two regressions: - The new cpuidle backend driver only works under hypervisors supporting the "SLPLAR" option, which isn't the case of the old POWER4 hypervisor and the HV "light" used on js2x blades - The cpuidle driver registers fairly late, meaning that for a significant portion of the boot process, we end up having all threads spinning. This slows down the boot process and increases the overall resource usage if the hypervisor has shared processors. This fixes both by implementing a "default" idle that will cede to the hypervisor when possible, in a very simple way without all the bells and whisles of cpuidle. Reported-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> Acked-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/powerpc/platforms/pseries/setup.c')
-rw-r--r--arch/powerpc/platforms/pseries/setup.c31
1 files changed, 21 insertions, 10 deletions
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index c11c8238797..54b998f2750 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -354,7 +354,7 @@ static int alloc_dispatch_log_kmem_cache(void)
}
early_initcall(alloc_dispatch_log_kmem_cache);
-static void pSeries_idle(void)
+static void pseries_lpar_idle(void)
{
/* This would call on the cpuidle framework, and the back-end pseries
* driver to go to idle states
@@ -362,10 +362,22 @@ static void pSeries_idle(void)
if (cpuidle_idle_call()) {
/* On error, execute default handler
* to go into low thread priority and possibly
- * low power mode.
+ * low power mode by cedeing processor to hypervisor
*/
- HMT_low();
- HMT_very_low();
+
+ /* Indicate to hypervisor that we are idle. */
+ get_lppaca()->idle = 1;
+
+ /*
+ * Yield the processor to the hypervisor. We return if
+ * an external interrupt occurs (which are driven prior
+ * to returning here) or if a prod occurs from another
+ * processor. When returning here, external interrupts
+ * are enabled.
+ */
+ cede_processor();
+
+ get_lppaca()->idle = 0;
}
}
@@ -456,15 +468,14 @@ static void __init pSeries_setup_arch(void)
pSeries_nvram_init();
- if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
+ if (firmware_has_feature(FW_FEATURE_LPAR)) {
vpa_init(boot_cpuid);
- ppc_md.power_save = pSeries_idle;
- }
-
- if (firmware_has_feature(FW_FEATURE_LPAR))
+ ppc_md.power_save = pseries_lpar_idle;
ppc_md.enable_pmcs = pseries_lpar_enable_pmcs;
- else
+ } else {
+ /* No special idle routine */
ppc_md.enable_pmcs = power4_enable_pmcs;
+ }
ppc_md.pcibios_root_bridge_prepare = pseries_root_bridge_prepare;