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powerpc/powernv/idle: Disable LOSE_FULL_CONTEXT states when stop-api fails

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Currently, we use the opal call opal_slw_set_reg() to inform the
Sleep-Winkle Engine (SLW) to restore the contents of some of the
Hypervisor state on wakeup from deep idle states that lose full
hypervisor context (characterized by the flag
OPAL_PM_LOSE_FULL_CONTEXT).

However, the current code has a bug in that if opal_slw_set_reg()
fails, we don't disable the use of these deep states (winkle on
POWER8, stop4 onwards on POWER9).

This patch fixes this bug by ensuring that if programing the
sleep-winkle engine to restore the hypervisor states in
pnv_save_sprs_for_deep_states() fails, then we exclude such states by
clearing the OPAL_PM_LOSE_FULL_CONTEXT flag from
supported_cpuidle_states. As a result POWER8 will be prevented from
using winkle for CPU-Hotplug, and POWER9 will put the offlined CPUs to
the default stop state when available.

Further, we ensure in the initialization of the cpuidle-powernv driver
to only include those states whose flags are present in
supported_cpuidle_states, thereby skipping OPAL_PM_LOSE_FULL_CONTEXT
states when they have been disabled due to stop-api failure.

Fixes: 1e1601b38e ("powerpc/powernv/idle: Restore SPRs for deep idle
states via stop API.")

Signed-off-by: Gautham R. Shenoy <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
This commit is contained in:
Gautham R. Shenoy 2017-08-08 14:13:15 +05:30 • committed by Michael Ellerman
commit 785a12afdb
2 changed files with 48 additions and 3 deletions
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10
drivers/cpuidle/cpuidle-powernv.c
View file

@ -235,6 +235,7 @@ static inline int validate_dt_prop_sizes(const char *prop1, int prop1_len,
return -1;
}
extern u32 pnv_get_supported_cpuidle_states(void);
static int powernv_add_idle_states(void)
{
struct device_node *power_mgt;
@ -248,6 +249,8 @@ static int powernv_add_idle_states(void)
const char *names[CPUIDLE_STATE_MAX];
u32 has_stop_states = 0;
int i, rc;
u32 supported_flags = pnv_get_supported_cpuidle_states();
/* Currently we have snooze statically defined */
@ -362,6 +365,13 @@ static int powernv_add_idle_states(void)
for (i = 0; i < dt_idle_states; i++) {
unsigned int exit_latency, target_residency;
bool stops_timebase = false;
/*
* Skip the platform idle state whose flag isn't in
* the supported_cpuidle_states flag mask.
*/
if ((flags[i] & supported_flags) != flags[i])
continue;
/*
* If an idle state has exit latency beyond
* POWERNV_THRESHOLD_LATENCY_NS then don't use it