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| author | Shreyas B. Prabhu <shreyas@linux.vnet.ibm.com> | 2015-04-20 08:02:58 +0300 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2015-05-22 08:12:30 +0300 |
| commit | 5703d2f4a1da6d23b3be896947ce255226fc4295 (patch) | |
| tree | 1ccff1655f657ff13c7f1a24fb6756b273db324d /arch/powerpc/include/asm/opal-api.h | |
| parent | d405a98c70ebbaa6ef276d7307d034a682321b95 (diff) | |
| download | linux-5703d2f4a1da6d23b3be896947ce255226fc4295.tar.xz | |
powerpc/powernv: Introduce sysfs control for fastsleep workaround behavior
Fastsleep is one of the idle state which cpuidle subsystem currently
uses on power8 machines. In this state L2 cache is brought down to a
threshold voltage. Therefore when the core is in fastsleep, the
communication between L2 and L3 needs to be fenced. But there is a bug
in the current power8 chips surrounding this fencing.
OPAL provides a workaround which precludes the possibility of hitting
this bug. But running with this workaround applied causes checkstop
if any correctable error in L2 cache directory is detected. Hence OPAL
also provides a way to undo the workaround.
In the existing implementation, workaround is applied by the last thread
of the core entering fastsleep and undone by the first thread waking up.
But this has a performance cost. These OPAL calls account for roughly
4000 cycles everytime the core has to enter or wakeup from fastsleep.
This patch introduces a sysfs attribute (fastsleep_workaround_applyonce)
to choose the behavior of this workaround.
By default, fastsleep_workaround_applyonce = 0. In this case, workaround
is applied/undone everytime the core enters/exits fastsleep.
fastsleep_workaround_applyonce = 1. In this case the workaround is
applied once on all the cores and never undone. This can be triggered by
echo 1 > /sys/devices/system/cpu/fastsleep_workaround_applyonce
For simplicity this attribute can be modified only once. Implying, once
fastsleep_workaround_applyonce is changed to 1, it cannot be reverted
to the default state.
Signed-off-by: Shreyas B. Prabhu <shreyas@linux.vnet.ibm.com>
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/include/asm/opal-api.h')
| -rw-r--r-- | arch/powerpc/include/asm/opal-api.h | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/powerpc/include/asm/opal-api.h b/arch/powerpc/include/asm/opal-api.h index 0321a909e663..a49e5fa6f939 100644 --- a/arch/powerpc/include/asm/opal-api.h +++ b/arch/powerpc/include/asm/opal-api.h @@ -165,6 +165,13 @@ #define OPAL_PM_WINKLE_ENABLED 0x00040000 #define OPAL_PM_SLEEP_ENABLED_ER1 0x00080000 /* with workaround */ +/* + * OPAL_CONFIG_CPU_IDLE_STATE parameters + */ +#define OPAL_CONFIG_IDLE_FASTSLEEP 1 +#define OPAL_CONFIG_IDLE_UNDO 0 +#define OPAL_CONFIG_IDLE_APPLY 1 + #ifndef __ASSEMBLY__ /* Other enums */ |